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Recycled materials relational database

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Title:
Recycled materials relational database design and implementation aspects
Physical Description:
Book
Language:
English
Creator:
McDonald, Rory Morgan
Publisher:
University of South Florida
Place of Publication:
Tampa, Fla.
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Subjects

Subjects / Keywords:
compendium
Microsoft access
industrial byproducts
database management system
waste materials
Dissertations, Academic -- Civil Engineering -- Masters -- USF   ( lcsh )
Genre:
government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
ABSTRACT: Although there has been a rise in the use of recycled materials in highway and geotechnical systems, many tons of potentially useful industrial and domestic by-products are still being discarded in the United States each year. While extensive research has been conducted to investigate the use of recycled materials in engineering applications, the dissemination of the findings is often limited. The problem is compounded by the lack of a single resource containing relevant engineering and environmental characteristics of each material; the tendency of the researchers to publish their findings in technical reports rather than archived publications; and the wide discrepancies among local and state environmental regulations and acceptability. A relational database is proposed as a method to improve implementation of recycled material research. A comprehensive review is conducted on data available for a wide variety of recycled materials and their usage in highway and geotechnical applications. Mechanical and environmental data and information from case histories are organized into approximately 10 tables in a relational database management system. More than 30 parameters, including engineering properties, availability and cost, are recorded for 23 materials in a highly-organized compendium. Through a simple user interface, a vast amount of data can be sorted to implement a recycled material program based on historic and current data. The DBMS is updatable and the design is amendable to account for future expansion.
Thesis:
Thesis (M.S.C.E.)--University of South Florida, 2004.
Bibliography:
Includes bibliographical references.
System Details:
System requirements: World Wide Web browser and PDF reader.
System Details:
Mode of access: World Wide Web.
Statement of Responsibility:
by Rory Morgan McDonald.
General Note:
Title from PDF of title page.
General Note:
Document formatted into pages;contains 105 pages.

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Resource Identifier:
aleph - 001478746
oclc - 56389573
notis - AJS2436
usfldc doi - E14-SFE0000388
usfldc handle - e14.388
System ID:
SFS0025080:00001


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ABSTRACT: Although there has been a rise in the use of recycled materials in highway and geotechnical systems, many tons of potentially useful industrial and domestic by-products are still being discarded in the United States each year. While extensive research has been conducted to investigate the use of recycled materials in engineering applications, the dissemination of the findings is often limited. The problem is compounded by the lack of a single resource containing relevant engineering and environmental characteristics of each material; the tendency of the researchers to publish their findings in technical reports rather than archived publications; and the wide discrepancies among local and state environmental regulations and acceptability. A relational database is proposed as a method to improve implementation of recycled material research. A comprehensive review is conducted on data available for a wide variety of recycled materials and their usage in highway and geotechnical applications. Mechanical and environmental data and information from case histories are organized into approximately 10 tables in a relational database management system. More than 30 parameters, including engineering properties, availability and cost, are recorded for 23 materials in a highly-organized compendium. Through a simple user interface, a vast amount of data can be sorted to implement a recycled material program based on historic and current data. The DBMS is updatable and the design is amendable to account for future expansion.
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Recycled Materials Relational Databa se: Design and Implementation Aspects by Rory Morgan McDonald A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering Department of Civil and Environmental Engineering College of Engineering University of South Florida Major Professor: Alaa K. Ashmawy, Ph.D. Manjriker Gunaratne, Ph.D. Rajan Sen, Ph.D. Date of Approval: June 25, 2004 Keywords: waste materials, database ma nagement system, industrial byproducts, Microsoft access, compendium Copyright 2004, Rory Morgan McDonald

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Dedication This work is dedicated to my wife, Anne and our newborn son, Dane Anne has been a tremendous support – sacrificing to stay hom e with our baby while I was finishing the research in preparation for the defense. Du ring the laborious proc ess of thesis writing, Dane provided much-needed stress relief in the form of father/son playtimes. The support and love of my whole family especial ly J.P., Jan, PGI, and the President allowed me the unparalleled opportunity of pursui ng a graduate degree in geotechnical engineering with Dr. Ashmawy at th e University of South Florida.

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Acknowledgement Several individuals and organizations made this effort possible. The Florida Department of Transportation funded the recycled materi als project through a research grant to the University of South Florida. Newel Wh ite, Amr “Sal” Sallam, and Jessica McRory provided high quality insights on technical issues. Paul Gillrie, Dave Houssian, and Adam Gillrie of the Paul Gillrie Institute sh ared their knowledge of database management systems. Materials and harassment were grac iously provided by R upert Bodden. Finally, Dr. Ashmawy deserves a special thanks not onl y for being the best professor with whom I have ever been in contact, but also for be ing an unexpected mentor and friend. He requires much from his students but gives them much more in return.

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i Table of Contents List of Tables................................................................................................................. .....v List of Figures................................................................................................................ ....vi Abstract....................................................................................................................... ......vii Chapter One: Introduction and General Literature Review...............................................1 Introduction................................................................................................................... ..1 Original Project Scope....................................................................................................1 Stabilizing Mechanisms..............................................................................................2 Proposed Tasks............................................................................................................2 Project Evolution............................................................................................................2 Problem Redefinition..................................................................................................3 Proposed Solution: Recycled Materials Relational Database.........................................4 Past Efforts: Comprehensive Resources.........................................................................4 Collins and Ciesielski, (1994).....................................................................................4 Chesner, Stein, Collins, and MacKay (1998)..............................................................5 Chesner, Collins, MacKay, and Emery (2002)...........................................................7 Current Effort: Recycled Mate rials Relational Database...............................................9 Database Organization..............................................................................................12 Connecting the Data..................................................................................................12 Subsequent Chapters.................................................................................................15 Chapter Two: Materials and Availability........................................................................16 Introduction................................................................................................................... 16 Material Selection.........................................................................................................18 Material Categories and Descriptions...........................................................................19 Category: Domestic Waste........................................................................................20 Category: Industrial Waste........................................................................................20

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ii Category: Mineral Waste...........................................................................................20 Description: Domestic Waste....................................................................................20 Description: Industrial Waste....................................................................................23 Description: Mineral Waste.......................................................................................27 Material Availability.....................................................................................................28 Observations.................................................................................................................29 DBMS Organization.....................................................................................................30 Materials Table.............................................................................................................31 Materials Form..........................................................................................................31 Chapter Three: Processing and Applications...................................................................32 Introduction................................................................................................................... 32 Applications..................................................................................................................3 2 Description of Applications..........................................................................................33 Embankmen t/Fill.......................................................................................................33 Flowable Fill..............................................................................................................33 Concrete Additive......................................................................................................34 Asphalt Pavement......................................................................................................34 Base/ Subbase............................................................................................................35 Stabilized Base..........................................................................................................35 Soil Reinforcement/ Stability....................................................................................36 Other.......................................................................................................................... 36 Processes...................................................................................................................... .37 Material Processing: An Overview...............................................................................37 User Interaction.............................................................................................................43 Application Table.........................................................................................................43 Application Form......................................................................................................44 Process Table................................................................................................................44 Process Form.............................................................................................................46 Chapter Four: Engineering and Envir onmental Properties and Performance..................47 Introduction................................................................................................................... 47

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iii Properties..................................................................................................................... .47 Engineering Properties..............................................................................................47 Omitted Engineering Properties................................................................................48 Environmental Properties.............................................................................................49 Organization and Input..............................................................................................50 Data Range................................................................................................................53 Evaluating Performance................................................................................................53 Plastics....................................................................................................................... 54 Incinerator Ash..........................................................................................................55 Scrap Tires.................................................................................................................55 Roof Shingles............................................................................................................58 Coal Byproducts (Fly Ash, Bottom Ash, Boiler Slag)..............................................58 Scrubber Base............................................................................................................59 Demolition Debris.....................................................................................................60 Slags (Blast-furnace, Steel-mill, Non-ferrous)..........................................................60 Kiln Dusts (Cement and Lime).................................................................................61 Reclaimed Asphalt Pavement and R eclaimed Concrete Pavement...........................62 Foundry Waste..........................................................................................................63 Paper Mill Sludge......................................................................................................63 Carpet Fibers.............................................................................................................64 Mill Tailings..............................................................................................................65 Phosphogypsum.........................................................................................................65 Quarry Waste.............................................................................................................66 Waste Glass...............................................................................................................66 Chapter Five: Database Design........................................................................................68 Identification of Tables and Fields...............................................................................68 Developing Data Relationships....................................................................................70 Table Relationships.......................................................................................................71 Content Overview.........................................................................................................72 Material Table...........................................................................................................72

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iv Applications Table....................................................................................................73 Process Table.............................................................................................................74 Performance Table....................................................................................................74 Other Tables..............................................................................................................75 Using the Database.......................................................................................................75 Forms.........................................................................................................................7 6 Queries.......................................................................................................................7 8 Reports.......................................................................................................................8 1 Interface...................................................................................................................... ..81 Navigating Existing Data Forms...............................................................................82 Navigating New Data Forms.....................................................................................82 Modification..................................................................................................................8 4 Chapter Six: Cost and Recommendations........................................................................85 Cost........................................................................................................................... ....85 Overview...................................................................................................................85 Considerations...........................................................................................................86 Cost Breakdown............................................................................................................86 Material Cost.............................................................................................................86 Installation Cost.........................................................................................................88 Life-Cycle Cost.........................................................................................................88 Environmental Cost...................................................................................................89 Database and Cost.........................................................................................................89 Recommendations.........................................................................................................90 General Recommendations........................................................................................90 Additional Research..................................................................................................91 Database Recommendations......................................................................................91 Conclusion....................................................................................................................9 2 References..................................................................................................................... ....93

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v List of Tables Table 2-1 Comprehensiv e Material Studies...............................................................17 Table 2-2 Recycled Materials for Current Research..................................................19 Table 2-3 Material Availabil ity (Million Tons per Year)..........................................29 Table 3-1 Database Application Categories...............................................................33 Table 3-2 Plastic Resins and their Source..................................................................38 Table 4-1 Database Engineering Properties...............................................................48 Table 4-2 Environmenta l Properties Tables...............................................................50 Table 4-3 Properties of Environmental Concern........................................................51 Table 4-4 Regulatory Methods Tests.........................................................................52 Table 4-5 Scrap Tire Leachate Summary in mg/L.....................................................57 Table 5-1 Types of Queries........................................................................................79

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vi List of Figures Figure 1-1 “Recycled Material s Information Database”...............................................7 Figure 1-2 “User Guidelines for Waste Materials in Pavement Construction”.............9 Figure 1-3a Hierarchical Model....................................................................................10 Figure 1-3b Relational Model........................................................................................11 Figure 1-4 Database Schema.......................................................................................14 Figure 2-1 Material Availability Bar Graph................................................................30 Figure 3-1 Scrap Tire Use for U.S. and Florida..........................................................40 Figure 3-2 Partial Process Table..................................................................................44 Figure 5-1 Part of th e Material Table..........................................................................69 Figure 5-2 Case Process Form (‘View Existing Data’)...............................................77 Figure 5-3 Process Form (‘Add New Data’)...............................................................78 Figure 5-4 Fly Ash Query Design...............................................................................80 Figure 5-5 Fly Ash Query Output................................................................................80 Figure 5-6 Fly Ash Custom Report.............................................................................81 Figure 5-7 Interface Flow Diagram.............................................................................84

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vii Recycled Materials Relational Database : Design and Implementation Aspects Rory Morgan McDonald ABSTRACT Although there has been a rise in the use of recycled materials in highway and geotechnical systems, many tons of poten tially useful industrial and domestic byproducts are still being discarded in the Un ited States each year. While extensive research has been conducted to investigate th e use of recycled materials in engineering applications, the dissemination of the findings is often limited. The problem is compounded by the lack of a single resour ce containing relevant engineering and environmental characteristics of each material ; the tendency of the researchers to publish their findings in technical reports rather than archived publications; and the wide discrepancies among local and state environm ental regulations and acceptability. A relational database is proposed as a met hod to improve implementation of recycled material research. A compre hensive review is conducted on data available for a wide variety of recycled materials and their usag e in highway and geotechnical applications. Mechanical and environmental data and info rmation from case hist ories are organized into approximately 10 tables in a relational da tabase management system. More than 30 parameters, including engineeri ng properties, availability an d cost, are recorded for 23 materials in a highly-organized compendium. Through a simple user interface, a vast amount of data can be sorted to implement a recycled material program based on historic and current data. The DBMS is updatable an d the design is amendable to account for future expansion.

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1 Chapter One: Introduction and General Literature Review Introduction Recycled materials provide an attractiv e alternative to traditional engineering construction materials such as asphalt, concrete natural aggregate and others. This is due in part to their suitable engineering propertie s, which allow them to be used as substitute materials in several transpor tation and geotechnical applic ations. Equally important, recycled materials offer both economic and environmental incentives. In addition to a lower cost in comparison to traditional materi als, their use has the potential to alleviate landfill problems as well as avert costs typically associated with their disposal. Original Project Scope Originally, the purpose of this project was to investigate the use of recycled materials in geotechnical and transportation a pplications. Specifically, it was concerned with marginal soils. Soft clays, muc k, organic deposits, and loose sand are often unsuitable for use in construction due to their less-than-desirable engi neering properties. Traditional methods of stabilizing these soils through in-situ ground improvement or replacement techniques are costly. Recycled ma terials such as scrap tires, plastics, ash, slag, and construction debris provide a viable alternative both for their relatively lower cost and desirable engineering properties. Furthermore, use of recycled materials prevents their disposal into landfills, whic h are approaching capacity across the country.

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2 Stabilizing Mechanisms Initially, it was proposed to investigate di fferent types of margin al soils stabilized with recycled materials. Particularly, th e interest was in examining two stabilizing mechanisms: discrete and homogenous. In disc rete stabilizing, indivi dual elements such as recycled plastic piles (RPPs) are driven into the soil to prevent slope failure and improve global stability. Homogeneous stab ilizing, on the other hand, refers to mixing much smaller particles of recycled materials su ch as plastics, ash, or carpet fibers with marginal soils to improve their strength. It was envisioned that by classifying these systems and identifying candidate applica tions, both construction methods and design procedures could be developed. Proposed Tasks Several components of the initial project were proposed. First, a comprehensive literature review was to be c onducted in order to gather avai lability information, technical specifications, and parameter data for several recycled materials. Then, through feedback from the State and District Florida Departme nt of Transportation offices, the procedure would be to categorize the types of marginal soils encountered and current solutions and then classify them according to the appropriate stabilizing mechanism. Next, a laboratory and field experimental program would be setup to investigate both prope rties of stabilized soils and mixing methods. This would allow for the development of design and construction procedures. Finall y, large-scale field evaluation s would be carried out as a means of testing design and construction procedures. Project Evolution During the first stage of the project, th e literature review, th e project began to evolve. Recycled material research was much more developed than originally anticipated – spanning some twenty years. The majority of early studies dealt with new material identification and laboratory testing to determine material properties (Collins and

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3 Ciesielski, 1994; Edil and Benson, 1998). More recent research has included large-scale field tests, predominantly environmen tal studies, and pro cessing technique characterization (O’Shaughnessy and Garga, 1999; Liu et al., 2000; C onsoli et al., 2002). Perhaps the most surprising finding was the relative lack of documented implementation programs. With so much quality research in recycled materials, it is clear that implementation has not kept pace. This point was tested and reinforced by means of a recycled material survey sent to the seven Florida Department of Transportation district offices. When representatives from each were asked to document use of recycled materials in their district, very few had had any experience to share. This supports a theory that a large gap exists between acad emic research on recycled materials and engineering practice and implementation. Problem Redefinition Despite current efforts, many tons of pot entially useful industrial and domestic by-products are still being disc arded each year. Moreover, implementation of recycled material programs at the state level has not kept pace with research. This phenomenon can be explained by several factors. Firs t, the lack of a single resource containing relevant engineering and environmental ch aracteristics of each material limits the dissemination of findings. This makes it difficult to adequately compare several materials before deciding to adopt one into practice. Second, researchers tend to publish data in technical reports, on line sources, and special publications as opposed to archived publications. Sorting through and finding pert inent information can be time-consuming and tedious. The wide discrepancies among lo cal and state environmental regulations in terms of material acceptability make it difficu lt to establish consis tent practices among various states and regions. Finally, the rapi d generation of new res earch exacerbates the existing logistics problem of data organization.

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4 Proposed Solution: Recycled Materials Relational Database A relational database is proposed as a method to organize current data, simplify the interface that the user encounters, and ultimately improve implementation of recycled material research. If the ga p discussed earlier is valid, then there must be a way to mitigate the separation between academic research in recycled materials and engineering practice. The initial effort will be centere d on a relational database. Essentially a collection of attributes that describe sp ecific objects, a relati onal database provides several advantages to traditional methods of organization. For example, such a database stores information in the form of related tables – allowing the same data to be viewed in different ways. It is not nece ssary for the user to know how th e data is related in order to meaningfully interact with it. Through fo rms, queries, and reports – the fundamental elements of any database management system the user can rapidl y sort through a vast amount of current, relevant da ta. Furthermore, the database management system is updatable and the design is amendable to account for future expansion. The result is an effective tool to aid in the implementation of recycled material research. Past Efforts: Comprehensive Resources Collins and Ciesielski, (1994) In conjunction with the National C ooperative Highway Research Program (NCHRP) and the American Association of State Highway and Transportation Officials (AASHTO), a study was undertaken to synthesize the information available on the use of waste materials in highway construction. Th e report sought to systematically compile useful information before disseminating it to the public. Primarily targeted at “administrators, policy makers, engineers, and others involved in highway construction,” the resource contains useful information regarding everything from design considerations and environmental aspects to the econom ics, availability, and actual highway construction use of waste materials (Collins and Ciesielski, 1994). Organized according to four source identifications: agricultural, domestic, industrial, and mineral wastes, the

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5 report addresses the gap theory by admitting th at “what has been l earned about a problem frequently is not assembled, costly research findings may go unused, valuable experience may be overlooked, and full consideration may not be given to available practices for solving or alleviating the problem ” (Collins and Ciesielski, 1994). Although somewhat lacking in detail their findings are nonetheless more comprehensive than previous work. Information is provided on at least 38 materials. In addition, several processes and applications as well as environmental issues are mentioned for each material. Actual uses in field construction are documented according to the state in which they took place. In ge neral, the source is a very good summary of research and practice in recycled material s before 1994. Excellent data on material availability and detailed stateby-state use of recycled materials in several applications are perhaps the best contributions. Unfortuna tely, the report lacks detail. Virtually no specific information is available on engineeri ng and environmental prope rties. Finally, as a printed report, there is still no relief fr om having to painstak ingly search for the information that is of interest. The only wa y to update the report is to produce a new one. Chesner, Stein, Collins, and MacKay (1998) Sponsored by the American Associati on of State Highway and Transportation Officials (AASHTO) and in connection with the Federal Highway Administration, the “Recycled Materials Information Database” wa s designed as a single source. Its stated purpose was to provide “a tool that could be used to access from a database, information on recycled material propertie s, applications, and testing procedures” (Chesner et al., 2003). The database is organized according to twenty waste materials and six applications. After choosing a material, ni ne primary tabs provide easily navigable access to 28 subcategories. The primary ta bs are: General Info rmation, Production and Use, Engineering Properties, Environmen tal Properties, Applications, Laboratory Testing, Field Testing, References, and c ontacts. The subcategories range from availability by region and chemical compositio n by material to construction procedures and bibliographical references. Figure 1-1 shows one screen from the database. The

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6 primary tab “Production and Use” and the se condary tab “U.S.A. Production” have been chosen for “Coal Fly Ash.” Availability or production data is presented in a state-bystate breakdown. Features also allow users to edit and delete both the text and existing tables or create new data tabl es and figures as new informa tion becomes available. In short, the “Recycled Materials Informati on Database” is a valiant effort aimed specifically at the bridging the gap. Perhaps the most important features of th e database are its attention to detail, its rigid organization and its fac ilitation of moving rapidly fro m one area of interest to another. With a click of the mouse, a user can browse trace metal concentration data for a particular material or view the availability of a different material state-by-state. Another helpful addition is the ability to upda te the existing resources. A user can add new data as it becomes available. Ther e are however, several drawbacks to this approach. First, the database has a hierarch ical relationship structure. Similar to a pyramid, this type of relati onship is top down. A user must start the search by first choosing a material, and then progressing to a subcategory involving that material. In order to compare data, it is necessary to go back to the beginning and choose a different material. A hierarchical model has two ma in deficiencies: 1) the user has to know something either about the subject or about the way in which the data is organized and related and 2) the user cannot search for sp ecific information in a specific subcategory without first going back to the beginning of the hierarchy. As a result of these limitations, the database can best be used by an individual with intimate knowledge of recycled material research.

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7 Figure 1-1: “Recycled Mate rials Information Database” (Chesner et al., 1998) Chesner, Collins, MacKay, and Emery (2002) As a result of recent fede ral initiatives for recycled material use in highway construction in the U.S., a project was unde rtaken to provide information on waste materials in specific applicati ons. In addition, the project sought to address issues of suitability for relatively unknown materials and identify areas in need of future research (Chesner et al., 2003). The result, “User Guidelines for Waste and Byproduct Materials in Pavement Construction,” is an online re source organized through twenty-one recycled materials and six applications. It is primarily an online ve rsion of a tec hnical report, providing users with access to information such as material origin, processing requirements, market sources, management op tions, and material properties (Chesner et al., 2002). Many of the tables and other general information in the user guidelines are borrowed directly from its predecessor, the “Recycled Materials Information Database.”

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8 Currently, no features exist that allow the us er to edit or add to existing information. However, the shear volume of information available makes it a valuable single, comprehensive resource. The advantages of the user guidelines ar e threefold. First, they are very wellorganized and detailed. Unlike the printed technical report by Co llins and Cielieski, material properties are available in the form of data tables. The second advantage is the user interface. It is both seamless and aes thetically pleasing – allowing the user to effortlessly move from one cate gory to the next with a click of the mouse. Finally, by making it available on the web, us ers are not required to download software or order it in report format. Instead they can simply go to the website and star t perusing. However, there are certain drawbacks. Like the databa se described previously, the user guidelines are set up as a hierarchical model. Th e user may only choose a material or a material/application combination before viewi ng the information appert aining to it. This feature requires the user to have some knowledge of recycl ed materials or at least how the information has been organized. The user cannot search an d sort by property, availability, chemical compositi on or any other subcategory fo r that matter. Similarly, the user has no ability to add, update, or delete information. This makes the useful life of the user guidelines somewhat limited. In Fi gure 1-2, the user guide lines page for scrap tires is reproduced.

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9 Figure 1-2: “User Guidelines for Wast e and Byproduct Materials in Pavement Construction” (Chesner et al., 2002) Current Effort: Recycled Materials Relational Database A new thread of recycled materials research has surfaced: compendium development. This research attempts to ad d to this thread. To be considered truly original and useful, the relational database must continue to build upon the positive advances of past studies and address the lim itations of those mentioned here. First, the database must be robust. Studies by Chesne r et al. (1998) and Chesner et al. (2002) satisfy this requirement through the large volum e of detailed data that they include. In the relational model presented in this thesis, some nine tables composed of more than 60 fields and comprising the work of almost 90 research studie s form the skeleton of the 15 mega byte database. By incorporating almost every possible category of information that may be of interest to both academics and engineering professionals, the recycled materials database is a one-stop single s ource that is comprehensive in nature.

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10 Further components that must be built upon rather than repl aced include data organization, detail, and user interface. The latter especially will be admittedly difficult to duplicate without a professiona l web designer. However, it is still possibl e to deliver an aesthetically pleasing, seamless interface, wh ich is user-friendly. The tables and fields are chosen to provide unpara lleled organization and maxi mum detail. The relational database model addresses limitations that are consistent among the other three efforts. First, access to queries improves searchabilit y. By creating a cust om query, a user can search for information from any table or any field and combine that information into one table for viewing. The user is not forced to se arch simply by material type or application. Therefore, the user is not required to ha ve previous knowledge of either recycled materials or the structure of the database. Th is is one of the advantages of a relational model in which all data is linked together as opposed to a hierarchical model in which initial choices lead to increasingly narrow br anches of data. Figure 1-3 and 1-4 provide an example of the hierarchical and re lational database model, respectively. Figure 1-3a: Hierarchical Model Level 1 Choice 1 Choice 2 Choice 3 A B C D E

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11 Figure 1-3b: Relational Model Two more important features are amenability and control of data entry. Only the project by Chesner et al (1998), allows th e user to add, edit, or delete data. However, doing so requires basic knowledge of database design. Also, there is no way to control data entry – to keep a user from inputting dup licate, false, or poorly-formatted data. In the relational model, data is inputted through simple forms that make up one branch of the interface. Field properties and indexing properties are changed so as not to allow duplications in specific data entries. In a ddition, pull-down boxes and validation rule settings prevent users from entering impr operly-formatted data. Finally, forms for viewing data are locked to prevent editing correctly-entered existing data. If any of these controls become burdensome or prove to be in adequate or inappropria te, they can easily be changed by a database designer. Choice 1 C D Choice 2 A B E

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12 Database Organization The database is organized with nine data tables serving as the framework. These tables are chosen both for their relevant impor tance as recycled material topics and for their ability to easily link the data together. The nine tabl es are Material, Application, Process, Performance, Case/Process, Ch emical Composition, Metal Concentration, Organic Concentration, and Leachate. The f unction of most tables is obvious from the name of that table. However, there are a few exceptions. The Process table not only contains descriptions of refining sequences but it also has keeps track of every unique combination of material and application (e .g., fly ash as a concrete additive). The Performance table essentially documents cas e studies by providing detailed references that correspond to a specific process. So for a study on carpet fibers used in soil reinforcement, the authors of the study, the full bibliographi cal reference, the year, and the state would be documented. The Case/Pro cess table acts as a ma trix of engineering properties. Each reco rd corresponds to a unique combinat ion of case study and process. For example, a record might be kept of a st udy by a particular resear cher to investigate the use of waste roof shingles in asphalt pavement. Connecting the Data Each of the first five tables has an ID field that serves as a primary key. In addition to serving as a unique identifier of the entire record, the primary key links each table to at least one other table through a fo reign key. The foreign keys contain the same numbers as the primary keys though they may or may not be unique. The last four tables, which are the environmental property tables only have primary ke ys. Because every table is linked to at least one other table and all nine tabl es are linked to the group, access to one table grants access to all tables. In Figure 1-5, tables and relationships are shown by way of a database organizational chart or schema. Each table name is bolded, and each primary key is underlined. The entries that are not bolded or underlined constitute the subfields within the tables. The lines between the tables indicate relationships that exist. The numbers above a nd below the lines, ‘1’ and ‘ ’ refer to one and many

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13 respectively. They characterize the relations hips (one-to-one, one-to-many) that exist between the tables generally and the primary and foreign keys specifically.

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14 MATERIAL IDMaterial MaterialName MaterialDescrip Availability PROCESS IDProcess IDMaterial IDApplication ProcessDescrip CostPerTon APPLICATION IDApplication ApplicationName ApplicationDescrip PERFORMANCE IDCaseStudy IDProcess Authors Reference Year State/Summary CASE/PROCESS IDCaseProcess IDProcess IDCaseStudy UnitWeight SpecificGravity Shape Size Absorption LL/PL Classification Hardness/CBR Cohesion MaxDryDensity InternalFriction OptWcontent CompressStrength Permeability EnvironNotes/Other 1 1 1 CHEMCOMPOS IDChemCompound IDCaseProcess PercentWeight METALCONCENTR IDMetal IDCaseProcess MetalConcen ORGANCONCENTR IDOrgCompound IDCaseProcess OrganicConcen/Class LEACHATE IDConstituent IDCaseProcess TCLP/SPLP EPTox/ASTM Fig. 1-4: Database Schema 1 Figure 1-4: Database Schema

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15 Subsequent Chapters Subsequent chapters consider the resear ch that has gone into the creation of the Recycled Materials Relational Database. Ma ny of the components th at were chosen for the database came about as a result of this res earch. However, the format of the database itself warrants additional development of t opics such as materials, applications, processes, properties, and performance. The fifth chapter puts it all together and builds on the topics presented in this chapter. Speci fically, it details the design of the database. A final chapter is included for recommendations and cost issues.

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16 Chapter Two: Materials and Availability Introduction Although several additional, e qually-important parameters exist in the realm of recycled material research, the majority of studies that have b een conducted typically begin with specifying the materials that are to be studied. In most cases, researchers select a material about which research has al ready been conducted in one form or another and test it to determine its pr edicted performance for a partic ular real-world application. Usually, there is some type of laboratory program that includes tests for grain-size distribution, plasticity limits direct shear, triaxial, and ma ny others. Researchers might also conduct mid-size experiments using testi ng apparatuses and procedures of their own design. For example, Bosscher et al. (1997) performed tests on model embankments in the laboratory so as to generate deformati on response data. Other studies have included full-size field testing programs. When used in conjunction with la boratory procedures, these studies have attempted to quantify the performance of r ecycled materials in various geotechnical and transportation applications. Most of the more recent recycled materi al research has focused on one of two aspects: 1) new ways of usi ng existing materials and 2) comp letely new materials or old materials processed in new ways. A study by Reid et al. (1998) examined the use of rubber tire chips as a method to reduce the bumps at the ends of bridges. This illustrates the specialized nature of some of these new ways to use existing recycled materials. Fahoum (1998) capitalized on local conditions by cons tructing a road-supporting embankment out of lime taken from the lagoon th at the road was to cross. Cleary, these two projects are c onsidered original. Unfortunately, a portion of the recycled mate rial research available is not quite as original. Sometimes, researchers simply rehash previously-performed experiments on

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17 old materials so as to valid ate prior findings. Certain wi dely available materials are clearly given preference over mo re obscure materials. This is not because the former are more promising. As a result, a vast amount of data is available fo r materials such as recycled tire shreds and fly ash, while a rela tively limited amount exists for mill tailings and phosphogypsum. Unfortunately, research is often repeated because of the difficulty in tracking down previous efforts. The tendenc y of researchers to publish their findings in technical reports, online sour ces, and in other special public ations rather than archived publications exacerbates the problem. A new research thread has developed around th is third aspect of recycled material research, and it is the subject of the current rese arch as well as that of at least three other studies (Collins and Cies ielski, 1994; Chesner et al., 199 8; Chesner et al. 2002). As described earlier, the first summarizes info rmation on 38 recycled materials, the second contains 20 materials, and the third pres ents 21 materials. The first study is a comprehensive technical report and the other tw o are online databases. The full extent of these efforts was outlined in Chapter 1. Fo r the purpose of the current study, it is sufficient to present the materials and provide some rationale for selecting those that will be part of this study. In Table 1-1, the ma terials included in each of the three earlier studies are marked. Notice the close overl ap of materials be tween the second two studies. This is no surprise as bo th have the same principal author. Table 2-1: Comprehens ive Material Studies Recycled Material Collins/Ciesielski (1994) Chesner et al. (1998) Chesner et al. (2002) Crop Wastes Logging/Wood Waste Miscellaneous Organics Paper/Paperboard Yard Waste Plastics Incinerator Ash (MSW) Sewage Sludge Scrap Tires Compost Used Oil Coal Fly Ash Bottom Ash

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18Table 2-1 Continued Boiler Slag Demolition Debris Blast-Furnace Slag Steel Mill Slag Non-Ferrous Slags Cement/Lime Kiln Dust Reclaimed Asphalt Pavement Reclaimed Concrete Pavement Foundry Wastes Silica Fume Roofing Shingle Waste Sulfate Waste Lime Waste Ceramic Wastes Paper Mill Sludge Contaminated Soils Quarry Waste Mill Tailings Coal Refuse Washery Rejects Phosphogypsum Baghouse Fines Carpet Waste Waste Glass Flue Gas Scrubber Material Selection There are several criteria by which materi als must be selected for the current research. First, and perhaps most importantl y, reliable data must be available about each material selected. With all the parameters us ed to describe the various materials still to be developed, it is a dubious idea to include an exciting new material about which there is little research available. Second, care must be taken not to duplicate any material. This could be a problem for certain materials, which can be processed in two or more drastically different ways. Another potential material redundancy problem occurs when one material can be referred to by more than one name. As a brief example, consider incinerator ash, which is also referred to as municipal solid waste combustor ash and waste-to-energy ash. With this in mind, care must be taken not only in the selection of materials stage but also during the data collec tion and entry stage. A final consideration

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19 for selection is that the data is updatabl e and the design is amendable. Any omitted materials may be added immediately and the future discovery of new materials may be added as the research becomes available. Though by no means a comprehensive list, the 24 recycled materials selected for this study provide a robust framework from which to launch the database. Moreover, they are representative of the r ecycled material research as a whole. Table 2-2 lists these 24 materials. Table 2-2: Recycled Materials for Current Research Paper Demolition Debris Paper Mill Sludge Plastics Blast-Furnace Slag Wood Waste Incinerator Ash (MSW) Steel Mill Slag Carpet Fibers Scrap Tires Non-Ferr ous Slag Mine Tailings Roof Shingles Cement/Lime Kiln Dust Phosphogypsum Fly Ash (Coal Ash) Reclaimed Asphalt Pavement Quarry Waste Bottom Ash (Coal) Reclaimed Concrete Pavement Glass Scrubber Base (Coal) Foundry Wastes Boiler Slag Material Categories and Descriptions This section serves as a background of and companion to the recycled materials database. In this section, a general descrip tion of each of the materi als is provided. This description includes the various terms used interchangeably that refer to the same material as well as the material’s indu stry origin and othe r general descriptive characteristics. Collins and Ciesielski (1994) suggest dividing the materials into four categories: agricultural, dome stic, industrial, and mineral. However, research of “agricultural” materials is extremely limited, an d the one material of interest from that category, wood waste, also fits in to the industrial byproducts category. For the purposes of this study, the 24 recy cled materials are divided into three categories based on general origin – domestic wa ste materials, industrial waste materials, and mineral waste materials. Although the literature suggests adding additional categories and subcategories to allow for a more detailed breakdown, the chosen categories are adequate. Additional categor ies would only serve to complicate user

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20 interaction with the database. It is conceivabl e that several of the materials could fit into multiple categories (i.e. roof shingles, scrap tires, plastic etc.), but they are included in only one here. Category: Domestic Waste Domestic waste materials comprise wa ste generated in the form of both commercial and household garbage. They are often called post-consumer materials. Domestic waste materials are as follows: paper waste, plastics, incinerator ash, scrap tires, glass/ceramics, and carpet wa ste (Collins and Ciesielski, 1994). Category: Industrial Waste Industrial waste materials are exactly th at – byproducts of industry. Industrial waste materials specified in this study are: roof shingles, fly ash, bottom ash, boiler slag, scrubber base, wood waste, demolition debris blast-furnace slag, steel mill slag, nonferrous slag, cement and lime kiln dust, reclaimed asphalt pavement, reclaimed concrete pavement, foundry waste, and paper mill sludge. Category: Mineral Waste Finally, mineral wastes result from mi ning activities or more specifically, the extraction of ores and minerals. Mineral waste materials: quarry waste, mill tailings, and phosphogypsum. Again, it must be emphasized that this list of mate rials is by no means comprehensive. Other waste materials exist and certainly a range of variations can occur from different processing techniques. However, the list is adequate for the intended use. Description: Domestic Waste Waste paper refers to trash in the form of newspapers, magazines, cardboard, and other miscellaneous paper produ cts. Although the vast major ity of this waste paper is

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21 recycled to produce other paper products, its limited use has been reported in highway applications though mainly in aesthetic a pplications (Collins and Ciesielski, 1994). Plastics are much more versat ile. Trash bags, plastic pipe s, milk jugs, battery casings, plastic cups/plates, and plastic soda bottles all are potential sources for waste plastic (Collins and Ciesielski, 1994). These sources are composed of various types of plastic resins among them polyethy lene terephthalate (PET) a nd high-density polyethylene (HDPE). In the past, resear chers have taken two very di fferent approaches to using plastics in engineering applications. As a result, they make use of two very different forms of the same material depending on the stabilizing mechanism desired: discrete or homogeneous. Discrete stabilizing incorporat es individual elements such as plastic lumber or plastic piles for the purpose of in terfering with a failure surface (Loehr and Bowders, 2000). Homogeneous stabilizati on on the other hand denotes mixing small pieces or strips of the plastic, usually PET fi bers from plastic bottles with soil, pavement, or concrete for the purpose of improving en gineering properties such as strength or stiffness (Consoli et al. 2002). Stabilizi ng mechanisms will be described in the application and field performance section of the paper. Another widely researched domestic wast e material is incinerator ash, also referred to as MSW ash. Burning of municipa l solid waste produces this type of ash. The residue is divided into two types – bottom ash and fly ash of which the vast majority is bottom ash. The bottom is lighter in color but because it is usually moist, it produces little dust. One the other hand, fly ash is a darker, fine, powdery substance (Chesner et al., 1998). Usually, the two are combined for di sposal. Recently, this material attracted negative attention by the EPA due to its tende ncy to leach high concentrations of heavy metals (Collins and Ciesielski, 1994). Perhaps the most extensively researched r ecycled materials currently, scrap tires, are gaining notoriety for their versatility. Potentially usable forms include whole tires, sliced tires, tire chips, tire shreds, and sma ller, soil-like particles referred to collectively as crumb rubber. The size of the tire chips is a function the shredding machine itself. To produce a smaller sized chip, it is often necessa ry to employ more than one processing machine (Bosscher et al., 1997). One tire sh red processing company produces a rough

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22 shred, a 2.5-4cm shred, a 1.25-2.5cm shred, a nd a 0.6-1.25cm crumb (Chesner et al., 1998). Depending on the processi ng method and intended application, the size of the crumb rubber can vary dramatically, from a semi-irregular 1.5cm crumb all the way down to a graphite-like powdery substance. In addition, the company produces a product it calls “fines.” Composed prim arily of various types of rubbe r, recycled tire shreds also contain carbon black, polymers, and fabrics as well as steel wire or belt materials (Chesner et al. 2002). Waste glass typically refers to any recycled, post-cons umer glass products. Such products include soda containers as well as wi ndows and similar materi als. The majority of recycled glass is used as feedstock for the production of ot her glass contai ners, but it is also used in engineering applications. As a product of superc ooling, it is composed primarily of silicon dioxide (sand) and sodium carbonate (Chesner et al., 2002). Further processing of the glass partic les yields a product that re sembles gravel or sand and exhibits properties similar to those material s. Material recovery efforts have been centered on Material Recover Facilities (Che sner et al., 2002). Ceramic waste, on the other hand, is usually produced in the form of materials rejected by factories such as porcelain and china but could al so be waste from the home in the form of toilets and sinks. Similar to glass, ceramics waste is crushed to resemble a fine aggregate. Carpet waste, also referred to as carpet fibers, consists of waste from industrial production and discarded consumer carpet. E ssentially, the material is made up of two layers. Yarn-like fabrics are connected by an adhesive SBR, st yrene-butadiene latex rubber (Wang, 1999). Nylon face fibers are clumped into the first layer. Before application of the adhesive, a “soft waste” can be produced, which is usually reused in various non-engineering applications (Wang, 1999). However, the post-adhesive carpet waste, or “hard waste” is of interest in this study. Randomly inserted discrete fibers are mixed with soil in small dosages. An investig ation of these mixtures will follow in this thesis.

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23 Description: Industrial Waste Roofing shingle waste consists of both discarded industrial waste shingles and surplus domestic shingles used on houses. Two types of byproducts are normally considered. The first type is “prompt roofing shingle scra p” or “roofing shingle tabs” (Chesner, 1998). This type is generated as new shingles are formed to their specified dimensions. The second type, “tear-off roof sh ingles,” is generated as existing roofs are replaced or removed. Consisti ng of asphalt, fiberglass, aggr egate and other additives in various concentrations, roof shingles waste is non-uniform. Similar to tire shreds, the type and size of roof shingles waste vari es dramatically depending on the processing mechanism. The waste can range from a well-graded, irregular ly-shaped, coal-like byproduct to poorly-graded, black, sand-sized fi nes. In either case, questions of contamination arise due to th e variation in exposure and age of the recycled shingles. Fly ash is a byproduct that results from th e combustion of coal. Predominantly a fine-grained, powdery material, fly ash boa sts a variety of appearances, chemical compositions, and material properties. These va riations are due to discrepancies in parent coal properties, burning mechanisms, and mate rial handling (Vipulan andan et al., 1998). Even so, constant constituents include sili ca, alumina, iron oxide, lime, and carbon (Vipulanandan et al. 1998). Four types of co al are burned to produce fly ash: anthracite, bituminous, lignite, and sub-bituminous. Indivi dually, they produce two types of fly ash, which are characterized by calcium oxide conten t. Class-F fly ash contains less than 10 percent CaO, and it comes from anthracitic or bituminous coal. Class-C fly ash contains more than 10 percent CaO, and it comes from lignite or sub-bituminous coal (Vipulanandan et al. 1998). For facility of data interaction, this study lumps both types of fly ash into a single material. The sagacity of this decision will be examined during betatesting. Another coal burning byproduct, bottom ash, consists of a dark gray, coarse, wellgraded material that is produced in combin ation with fly ash (Chesner et al., 1998 and Chesner et al., 2002). Bottom ash is usually darker in color and consists of slightly larger particles. It is consider ed both coarser and more porou s than fly ash although the

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24 particles are about the same size as sand. Furt her differentiation of th ese materials can be found in the process sec tion of this report. Boiler slag and bottom ash are very similar materials. First, they both are byproducts of the coal burning pr ocess. Second, they exhibit very similar physical and mechanical properties. In fact, the two are often combined by researchers and considered as a single material. However, the production of either bottom ash or boiler slag depends on the type of coal-burning furnace. Moreover, the appearance of boiler slag is “coarse, hard, black, angular, and glassy ” (Chesner et al., 2002). It is poorly-graded and smooth in texture, and it is generated in much lowe r quantities than both fly ash and bottom ash. As an afterthought to initial research effort s, boiler slag and bottom ash were separated and now serve as distinct materials for the purposes of this research. Scrubber base is the term given to a compos ite recycled material. Also referred to as general sulfate waste or as FGD scrubber ma terial, it is an equal parts mixture of flue gas desulfurization sludge (FGD) and fly ash (Vipulanandan and Basheer, 1998). The former originated from a method to reduce SO2 emissions during the burning of coal in electric power plants. This scrubber syst em as it is termed yields a whitish calcium sulfite or calcium sulfate slurry. Calcium sulfite slurries are thixotropic and are generally more difficult to handle and treat than calci um sulfate slurries (Chesner et al., 2002; Collins and Ciesielski, 1994). Wood waste is a collective term for compost and construction byproducts from wooden structures such as homes, fences, docks et c. It is wasted in the form of “logging residues, wood and bark chips, and sawdust” from sawmills (Collins and Ciesielski, 1994). The few researchers who have examined this waste material have examined it exclusively in mulching applications and some lightweight fill applications. However, it is envisioned that this material will play a significant role in future research efforts. Demolition debris or C&D as it is referred to, is the general term for a host of waste materials generated from the cons truction industry. C onsisting of building materials such as concrete, gla ss, brick, and metal as well as other materials such as wood and plaster, C&D waste must be processed before it can be incorporated into engineering uses (Collins and Ciesielski, 1994). Similar to glass and roofing shingles, C&D waste is

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25 essentially a non-uniform materi al, making its comprehensive characterization difficult. Likewise, sorting poses a problem. Like roof shingles, C&D waste raises the question of possible contamination from asbestos and ot her hazardous materials. Some researchers have considered construction and demolition debris as a parent category for both reclaimed asphalt pavement and reclaimed c oncrete pavement. However, the three materials are separated in this study. Several materials belong to the genera l category of industr ial waste byproducts collectively referred to as sl ags. Two varieties exist: iron/steel slags and non-ferrous slags. Blast-furnace slag is a nonmetallic byproduct of producing iron in a blast furnace. Its chemical and physical properties vary acco rding to cooling the molten slag byproduct. The different processes produce four types of blast-furnace slag: air-cooled slag or expanded slag, palletized slag, an d granulated slag (Chesner et al., 2002). It is composed mostly of silicates and alumino-silicates of lime (Collins and Ciesielski, 1994). The resultant aggregate materials va ry in porosity and unit weight. Steel slag is a byproduct of the steel-making pr ocess. It is ini tially generated as a molten liquid, but it solidifies as it is c ooled. The reaction of lime flux with metal produces steel slag, which is made up mainly of oxides and silicates. There are several grades of steel based on carbon content. Depending on the grade of steel that is produced, steel slag occurs as one of four s ub-materials: tap slag, raker slag, synthetic slag, or cleanout slag (Chesner et al., 2002). Steel slag re sembles aggregate although the particles are generally harder and heavier. As the name implies, non-ferrous slag s are generated from the recovery and processing of natural ores ot her than iron. Primarily, this includes copper, phosphate, lead, nickel, and zinc (Chesner et al., 2002) Copper and phosphate slags are the most prevalent. Like steel slags, the initial molten byproduct evolves into a hard, aggregate material as it is cooled. The color and ge neral appearance of non-ferrous slags varies with their parent ores. Nonferrous slags can be dark blac k to brown or red and either glassy or dull depending on the metal from which they were processed and the method used. Obviously, non-ferrous slags are rea lly the name given to several different

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26 materials that exhibit similar albeit unequal properties. Beca use non-ferrous slag data is limited, the materials will all be included under the non-ferrous slag material heading. Kiln dusts in general are “fine by-pr oducts of Portland cement and lime hightemperature rotary kiln production operations th at are captured in the air pollution control dust collection system” (Chesner et al., 2002). Cement and lime kiln dusts are both fine, dry, powdery substances. A lthough physically similar, th e materials exhibit very different chemical properties. While cement kiln dust can contain reactive calcium oxide, lime kiln dust is potentially more reactive due to its free lime com position (Collins and Ciesielski, 1994). Both dusts may contain hazardous wastes. Although they could potentially fit in to the category of construction and demolition debris, both reclaimed asphalt pa vement and reclaimed concrete pavement have been researched and used extensivel y enough to warrant their own citation here. Also known as RAP, reclaimed asphalt pavement is generated as roads are repaired or replaced. RAP consists of asphalt and aggr egate and must be processed to become a usable recycled material. Before processi ng, the material resembles non-uniform oversized aggregate. The compos ition of reclaimed concrete pa vement (also referred to as reclaimed concrete material, recycled concre te pavement, or RCA) varies more than the composition of RAP (Papp et al., 1998). Cement structures such as roads, bridges, sidewalks, buildings, foundations, and retainin g walls can generate reclaimed concrete pavement material. Because the method of installation, exposure to environments, and concrete type and quality can all vary dramatically among these structures, uniformity in type and quality of reclaimed concrete pave ment is difficult to achieve (Collins and Ciesielski, 1994). The processed materi al is a well-graded gray aggregate. Foundry waste is used in metal casting plants, and it is composed of uniform silica sand or furnace dust (Edil and Benson, 1998). The clean sand becomes compromised during casting resulting in a mixture of sand, bentonite, and sea coal collectively referred to as “green sand” (Abichou et al., 1998). The waste sand’s bentonite component varies. There is some question as to the presence of chemicals, trace metals, and stones even in the proces sed waste material. The final product is poorly-graded.

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27 Paper mill sludge is a by-product of the pulp and paper industry. Edil and Benson (1998) cite residues from wastewater treatment plants at paper mills as the primary source for this material. The sludge, composed of mineral fines such as kaolinite and calcite, is generally considered an inorganic waste. The mate rial is also mixed with sand to produce a more uniform aggregate-type ma terial. Another by-pr oduct of the industry is spent sulfite liquor, a promising material for future geotechnical testing (Collins and Ciesielski, 1994). Description: Mineral Waste Quarry waste is a general term for any material that is generated from the processing of stone at quarries A series of processes produ ces different types of quarry waste: screenings, setting pond fines, and baghous e fines. For the current research, they will be treated as one material. Both the consistency and composition of this waste varies with the geographic location of the quarry, but the product is usuall y characterized by small pieces of chipped rock and fines. Mill tailings are a byproduct from the or e concentration processes. They are produced initially in slurry fo rm. Typically, the parent ores include iron, copper, lead, zinc, and uranium among others (Collines and Ciesielski, 1994). Mill tailings range in size from sand to silty-clay, but the particles are generally characterized as hard, angular, aggregate-type material composed of significantl y large fractions of fines. Like many of the other materials, mill tailings vary great ly in terms of particle size, physical and chemical properties. This is due to a variety of factors such as processing, disposal, type of ore etc. Phosphogypsum, sometimes included in the more general category, sulfate waste, is another mineral waste material. It is generated from the production of phosphoric acid from phosphate rock (Collines and Ciesiels ki, 1994). Composed of calcium sulfate hydrate, the final by-produc t is a wet, gray, silt-sized substa nce. There are concerns as to its impact on the environment as expres sed by the EPA over radon contamination

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28 (Collines and Ciesielski, 1994). However, the shear volume of phosphogypsum produced, especially locally, ma kes it an interesting materi al byproduct to include here. Material Availability Availability data is widely scattered and difficult to concretize. This is due mainly to two factors. First, availability of materials changes each year, and there is currently no resource availabl e that tracks these changes. Second, researchers tend to publish their findings on indivi dual materials in technical reports and online sources rather than archived publications. This make s the process of comparing availability data supplied by researchers tedious and timeconsuming. The comprehensive relational database approach is envisioned as a way to not only organize availability data from a variety of sources, but also track annual change s in the data. A brief attempt is made here in Table 2-3 to present organized, material availability data to provide a robust framework for the purpose of comparison.

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29 Table 2-3: Material Availability (Million Tons per Year) Recycled Material Name Collines/Ciesielski (1994) Chesner et al. (1998) Chesner et al. (2002) Paper 71.8 Plastics 14.4 Incinerator Ash (MSW) 8.6 9 9 Scrap Tires 2.5 280 280 Roof Shingles 10 11 Fly Ash (Coal Ash) 48 54.8 59.4 Bottom Ash (Coal) 14 16.1 16.1 Scrubber Base (Coal) 18 23.8 23.8 Demolition Debris 25 Blast-Furnace Slag 16 15.5 Steel Mill Slag 8 8.3 8.3 Non-Ferrous Slag 10 9 9 Cement/Lime Kiln Dust 24 18.2 18.2 Reclaimed Asphalt Pavement 50 45 45 Reclaimed Concrete Pavement 3 Foundry Wastes 10 15 15 Paper Mill Sludge Wood Waste 70 Carpet Fibers 2 Mine Tailings 520 500 500 Phosphogypsum 35 35 35 Quarry Waste 175 175 175 Glass 12.5 10.1 10.2 Boiler Slag 4 2.6 2.6 Observations There are several interpretations that can be made from Table 2-3. The oldest source contains availability data for the greates t number of materials. This fact makes it impossible to do a comprehensive comparison of availability data for all materials over time. Even so, the availability data for mate rials considered in each of the three sources shows a slight increase, generally speak ing. There are howev er, a few noticeable exceptions and at least one dras tic outlier. The avai labilities of non-fe rrous slags, kiln dusts, reclaimed asphalt pavement, and glass all s eem to have decreased slightly in recent years. Perhaps these decreases are a resu lt of increased indus trial efficiency and conscious internal reuse of byproducts or perhap s they are a result of less-than-efficient data collection. This latter reason may account for the drastic change in scrap tire

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30 availability from 2.5 million tons annually in 1994 to 280 million tons annually in 1998 and 2002 (Collins and Ciesielski, 1994; Ches ner et al., 1998; Chesner et al., 2002). Figure 2-1 contains a visual repres entation of material availability. 0100200300400500600 Paper Plastics Incinerator Ash Scrap Tires Roof Shingles Fly Ash Bottom Ash Scrubber Base Demolition Debris Blast-Furnace Slag Steel Mill Slag Non-Ferrous Slag Kiln Dust RAP RCM Foundry Wastes Paper Mill Sludge Wood Waste Carpet Fibers Mine Tailings Phosphogypsum Quarry Waste Glass Boiler Slag Figure 2-1: Material Ava ilability Bar Graph (Collins and Ciesielski, 1994) DBMS Organization This section describes a relational da tabase model to handle organization and storage of recycled material data. A review of the entire creation and maintenance of the database is available in Chapter 7. The intere st here is how the materials themselves and their availability fit into the database and how the user can interact with that data.

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31 Materials Table A materials table is generated using the database management system. There are 24 records (rows) corresponding to the 24 materi als used in this study. There are also four fields into which the data is stored: MaterialName, IDMaterial, MaterialDescription, and Availability (million tons/year). The data types for these four fields are text, autonumber, memo, and number long integer. The database designer may, of course, add additional materials not found in the original 24-material list. When a new material is added, the autonumber field, IDMaterial auto matically increments and assigns a unique number to that new material. For example, as it stands now, if the material fluorogypsum were added to the table, it would be assigned an IDMaterial of 25. IDMaterial serves as a unique record identifier within the Materials table, and functions as the primary key of the table. Its function is to link the Materials table indirectly to the rest of the database and directly to the Process table. The exis tence of the same field, IDMaterial, in the Process table establishes the link between both tables by serving as the foreign key. Materials Form Two separate forms are based on the Material s table. The first, ‘Materials Form,’ (green and yellow) is used to view exis ting data. It opens up directly after the switchboard and launches a sequence of nine forms. The user has the option of scrolling through records of data or moving on to the ne xt form. The data is locked so that no additions or edits can occur. The second fo rm, ‘Materials Form (Add Entry),’ (red and gray) does not allow the user to view existi ng data, but instead presents a blank form where the user can enter new data. The same sequence of nine forms is followed.

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32 Chapter Three: Processing and Applications Introduction Although some researchers skip directly from material selection to laboratory and field testing, they miss out on important parameters that more narrowly define and distinguish the materials. As a result, those w ho wish to validate exis ting data or build on previous studies are left to their own intu ition and deductive reasoning when it comes to reproducing the same material for testing. Tw o additional parameters should be specified to rigidly define the materials: processing an d application. Processing in this context refers to the preparation, trea tment, and conversion of the material from its raw form to a more refined form. Whether the material is processed directly from a parent waste material or collected as a byproduct of external activity, the process spans from origin all the way to use or testing. Application, on the other hand, generically defines how a material will be used in practice or how it is envisioned to be used in practice. A material’s envisioned application is very di fficult to determine from simply reviewing laboratory material parameter tests. The object ive is that the material name, its process, and its application will coalesce to ri gidly define each recycled material. Applications Past research efforts have examined act ual and envisioned applications that range from the mundane and ordinary to truly i nnovative and specialized. An example of the latter was described in the previous chapter. Researchers used tire shreds to mitigate the development of “bumps” at the ends of bridges (Reid et al., 1998). Although some of these specialized applications are mentioned here, they are not included directly within the database framework. Instead, eight general geotechnical and transportation

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33 applications were chosen to characterize some of the more mainstream recycled material research. Table 3-1 presents these applications. Table 3-1: Database Application Categories Embankment/Fill BaseSubbase Flowable Fill Stabilized base Concrete Additive Soil Reinforcement/Stability Asphalt Pavement Other Description of Applications Embankment/Fill The geotechnical or transportation defin ition of an embankment is a constructed, raised, earthen mound, composed of soil, aggreg ate, and other materials. Its purpose is to raise the level of a road relative to the surrounding area (Chesner et al., 2002). Constructed with similar materials, a fill differs in that it is used to cover an area below the surrounding ground surface or to fill in the space behind a retaining wall. Typically, an embankment or fill is composed of several material layers that must simultaneously maximize strength and permeability while mini mizing deflection. Because of the large quantities of earthen material required for both embankments and fills, recycled materials offer an attractive, low-cost alternative to expensive borro w material (Vipulanandan and Basheer, 1998). Moreover, recycled material s often exhibit engine ering properties that make them more desirable than traditional ma terials without even accounting for the cost differential. For example, the relatively low unit weight of tire shreds can potentially reduce pressures on retaining walls or lessen the load of an emba nkment constructed on top of marginal soil. Flowable Fill Consisting primarily of fine aggregat e, water, and a cem entitious component, flowable fill acts as a rapidlyhardening slurry (Chesner et al., 2002). Its main function is

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34 to fill in irregular nonuniform excavations, which require on ly very low bearing strength. There exists some discrepancy in the literature as to its exact constituent components. However, its formal description as a “cont rolled low-strength material” that exhibits properties of both concrete and soil-cement is unambiguous (Vipulanandan et al., 1998). Alternate names for flowable fill include lean-mix backfill, flowable mortar, and controlled-density fill (Vipulanandan et al ., 1998). Recycled materials are sometimes substituted for traditional fine aggregates such as sand. They may also serve as pozzolanic materials – replacing conventional cementitious components. Pozzolanic is the term given to siliceous materials that exhibit cementitious properties when combined with an activator in the presence of water (Chesner et al. 2002). Concrete Additive Portland cement concrete is used in rigid pavements, sidewalks, retaining structures, and bridge components. Made up of coarse a nd fine aggregate in addition to cement paste, Portland cement concrete also contains cementitious materials and chemical modifiers (Chesner et al., 1998). Recycled materials may be used in place of aggregate or again as pozzolanic cementitious components. The latter is the catalyst through which important physical propertie s of the concrete can be modified. Asphalt Pavement The layers of asphalt, aggregate, binder and other materials that make up asphalt pavement serve as a mechanism to distribute traffic loadings to underlying base and subbase layers. This application encompasses hot and cold mix asphalt as well as surface treatments. Hot and cold mix asphalt differ in both requisite preparation and expected performance. Hot mix asphalt re quires the addition of a mineral filler. It must be mixed at a plant, and can be used anywhere while cold mix asphalt can be mixed on site and is only used in lightly-trafficked rural areas (Chesner et al ., 2002). Applied as a liquid, surface treatments improve only existing road surfaces. Besides their potential use as

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35 substitutes for conventional aggregate in pave ments, recycled materials may be used as mineral fillers. The purpose of mineral fillers is to improve stiffening of the hot mix and increase individual particle contact (Chesner et al., 2002). As a result, they establish critical performance characteristics of the asphalt pavement. Base/ Subbase Below the asphalt surface layer lie the ba se and subbase layers of the pavement. Although both are composed of aggregates, th e gradation of these aggregates and the function of the two layers allow them to be treated separately. Ba se layers consist of higher fines content and their purpose is mainly load-beari ng and strengthening in nature (Chesner et al., 2002). Located directly below the pavement surface, it must simultaneously promote drainage and dissip ate stress to protect the subgrade. The subbase layer is located below the base, and it functions primar ily as a foundation. Opportunities for recycled material substituti on exist for this application as well. Highstrength materials can replace sand and gr avel as the principal base and subbase aggregates. Stabilized Base Stabilized base is considered a different “class” of base or subbase materials. Similar to the functions of ot her base layers, its purpose is to improve strength and to more efficiently distribute direct traffic load s to underlying layers (C hesner et al., 2002). The main difference is in composition. A mixt ure of aggregate, cementitious particles, and water, stabilized base gains stre ngth through compaction. Two terms used interchangeably for stabilized base are soil-cement and roller-compacted concrete. Not surprisingly, recycled materi als can be substituted as ag gregate or in place of the cementitious particles.

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36 Soil Reinforcement/ Stability Although not included as a separate a pplication in compre hensive recycled material research efforts, significant data exists pertaining to soil reinforcement and stability. In the past, accepte d techniques for dealing with reinforcement of marginal soils included the use of synthetic materials such as geotextiles and geofabrics, chemical stabilizers, and advanced al beit expensive soil improvement procedures such as jet grouting, deep dynamic compaction, and vibroflotation. Homogenous stabilization of these problematic soils can be accomplished by using small strips or fibers of various recycled materials (Consoli et al., 2002; Wang, 1999). Sl ope stability problems have been solved in the past with the use of so il nailing, micropiles, retaining structures, and shotcrete. However, promisi ng alternatives exist such as improving slope stability with discrete stabilization us ing waste materials (Loehr and Bowd ers, 2000). In general, this application follows two main stabilizing mechanisms: discrete and homogeneous stabilization. The former has more to do with stability and the latter with soil reinforcement. Other It is difficult and possibly even detrim ental to include every possible application for recycled materials either here or as part of the database. Providing an “other” category ensures that even the most obscure and questionable application receives the necessary attention and documentation. Many of these applicatio ns are considered specialized applications for specific circumst ances and conditions. However, if any one application in this category gains notoriety and becomes th e subject of several future research efforts, its status can easily be promoted through the creation of its own category. For current purposes of user acces s and organization, the “other” category will encompass anything that does not fit into the first seven application categories.

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37 Processes Most of the research on recycled mate rials simply glosses over or completely neglects to mention the material origins and requisite processing. Not only does this practice make duplication of results impossible (since there is no way to ensure that the same material is being tested), but because th e process is not described, it is unclear how difficult, expensive, and timeconsuming it is to process th e material once it has been acquired. Simply put, the breadth of proce ssing techniques is staggering. A process could be as straightforward as stockpiling th e material before us e or it could be as complicated as a long sequence of treatments requiring several processing machines just to refine it. Furthermore, a process dramatical ly affects the properties that a material will exhibit. This is why a material such as tire chips must be processe d differently for use in an embankment than for use in asphalt pavement. Material Processing: An Overview The processing of waste pa per and paperboard products is simple. Paper in the form of cardboard boxes, newspapers, magazines, and office paper is recycled through community programs. The paper is collected, so rted, and then shredded before it is used as mulching material and even slick pape r hydraulic mulch oversprays (Collins and Ciesielski, 1994). Unlike paper, plastics originate from a variety of sources and must be processed differently for each application. Table 3-2 show s the six types of plastic resins and their sources. Plastic lumber is formed from reclaimed HDPE, pellets are formed from recycled LDPE and prepared for use as the modifier in asphalt pavement, and a type of polyester is formed from recycled PET to chemically aid in the production of polymer concrete (Collins and Ciesielski, 1994). When used to stabilize cohesionless soils, plastic PET bottles are cleaned, chopped into pieces, and melted in an oven. Afterwards, the filaments are extruded and allowed to cool be fore they are stretc hed (Consoli et al., 2002). The mechanism here is homogenous st abilization. Loehr and Bowders (2000)

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38 combined recycled plastic, saw dust, and ot her materials to form composite recycled plastic piles (RPPs) used in discrete stabilization. Table 3-2: Plastic Resins and their Source Resin Name Source Low-density polyethylene PET film/trash bags Polyvinyl chloride PVC pipes/flooring High-density polyethylene HDPEmilk jugs Polypropylene PP battery casings/luggage Polystyrene PS egg cartons/cups Polyethylene terephthalate PET soda bottles MSW incinerator or combustor ash is generated from the combustion of municipal solid waste in one of two types of waste combus tors: mass burn facilities or refuse derived-fuel (RDF) fac ilities (Chesner et al., 2002). The former handles raw solid waste while the latter require s shredded and presorted sour ce materials to ensure the absence of deleterious elements. The resulti ng ash consists of grat e ash, siftings, boiler ash, and baghouse ash; the waste stream may be either combined or separated. The ash that sticks to the grate after combustion is bottom ash whereas boiler ash starts in the primary combustion zone but is later carried into both the gas stream and the pollution control system where it is co llected (Chesner et al., 2002). Scrap tire processing has developed as an industry by itself. Used for everything from tire derived fuel (TDF) and pla yground surfaces to mulch and aggregate replacement, scrap tires are processed in a variety of ways. Humphrey et al. (1998) suggests shredding whole tires before passi ng them through a sieve to meet gradation requirements. Several machines are required to process the tires into more refined forms. A cutting machine simply splits tires to form slit tires whereas tire shreds require a shredder, a machine with reciprocating knives that move forward and back to both tear and cut the tire (Chesner et al., 199 8). Because of their small size, tire chips (13 to 76 mm) must go through two rounds of shredders and the secondary shredder reduces the size and increases uniformity in shape. To produce ground rubber (0.15 to 19 mm), a granulator or grinding machine is first used to reduce size be fore exposed steel belts are removed through magnetic separation. Fibe rs are removed by air separation, and the

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39 resulting material is screened and sized (Chesner et al., 1998; Chesner et al., 2002). Crumb rubber (0.075 to 4.75 mm) is generated from one of three processes: the crackermill process uses rotating steel drums, the granulator process uses revolving steel plates, and the micro-mill process produces th e finest particles (Chesner et al., 1998). Two distinct processing mechanisms are necessary for pavement applications. If used as a substitute for aggregate, dry ground rubber is added to the hot mix asphalt. The wet process on the other hand, uses crumb r ubber as an asphalt modifier to produce rubberized asphalt (Chesner et al., 2002).

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40 U.S. ApplicationsTDR 76% Stamped 4% Engineering 5% Ground rubber 6% Agriculture 2% Exported 7% Florida ApplicationsEnergy 46% Crumb rubber 25% Export 1% Disposal 15% Engineering 13% Figure 3-1: Scrap Tire Use for U.S. and Florida (L iu et al., 2000 and DEP, 2003) Roof shingle waste originates as prom pt shingle scrap (t abs) from shingle manufacturers or as tear-off sc rap from contractors. Typically, the material is presorted to remove deleterious materials such as nails other metal, and wood before it is passed

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41 through a processing machine that reduces it s size. The final product may resemble anything from 75 mm partial shingl e pieces to a much finer, black, soil-like material. In either case, it is important to be aware of ri sks associated with asbestos contamination. Currently, one of the main processing inconsis tencies, which results in varying qualities of final product, has to do w ith the mixing of raw roof sh ingles from several sources during collection. Future research may address this issu e. When used as an asphalt pavement modifier, prompt shi ngle waste must first pass through a rotary shredder before its size is reduced further with a high-speed hammermill; then it is stockpiled (Chesner et al., 2002). Because fly ash has so many engineering applications, care must be taken to process the material appropriately. As a concrete additive, fly ash in dry form is used as a mineral admixture where consistent quality is important (Chesner et al., 2002). As a mineral filler in asphalt pavement, fly ash in dry form is collected and stored. Used as cementitious material in stabilized bases, fl y ash takes the place of binder although an activator must be mixed with it to serve as a catalyst for pozzolani c activity (Chesner et al., 2002). In flowable fill ap plications, fly ash is mixed wi th sand and/or cementitious material whereas embankment applications onl y require that it be stockpiled and brought to optimum moisture content before compaction (Chesner et al., 2002; Vipulanandan et al., 1998). Collected from the bottom of coal-burning furnaces, bottom ash is removed by water jets before “dewatering, crushing, a nd stockpiling” (Chesner et al., 2002). For asphalt pavement uses, bottom ash and boile r slag are screened and blended with conventional aggregates, and pyrites are re moved with electromagnets. Screening, grinding, moisture control, and the removal of contaminants round out the processes required for use in base, stabilized base, and embankment applic ations of these two materials (Chesner et al., 2002). In the materials section, the desulfurization process required to produce FGD scrubber base was outlined. In addition to th is step, the material must undergo forced oxidation or blowing air into th e holding tank to convert CaSO3 to CaSO4 (Chesner et al., 2002). Next the material is subjected to either a centrifuge or a belt filter for dewatering

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42 purposes. A dry material is a dded to stabilize the scrubber be fore it can be fixated, or modified chemically with quicklime or fly ash (Chesner et al., 2002). Demolition debris, reclaimed asphalt pave ment, and reclaimed concrete pavement are all processed similarly. After C&D waste has been sorted to remove wood, drywall, plastic etc., it is reclaimed a nd crushed to be used in the place of aggregate (Collins and Ciesielski, 1994). Similarly, RAP and RCA ar e also crushed, screened, and stockpiled although magnetic separators must be used to remove reinforcing steel in RCA (Chesner et al., 2002). Blast-furnace slag is crushed and screen ed to meet gradation requirements, but properties must be tested before use because of inconsistencies in the material (Chesner et al., 2002). As a concrete additive, it must be milled very fine. Steel mill slag must also be crushed and screened prior to use, but other criteri a such as moisture content, handling, and hydration expansion must be addressed (Chesner et al., 2002). Similarly, non-ferrous slags are crushed, screened, a nd blended with traditional aggregate. Mixing small percentages of kiln dust with aggregate and asphalt produces one type of concrete additive. In addition, kiln dusts may be pelletized for use as synthetic aggregate (Chesner et al., 2002). Waste foundry sand requires crushing, reci rculating, and screening to remove large particles. The waste sand is then st ockpiled according to particle size (Abichou et al., 1998). Paper mill sludge processing has been the subject of very little research. However, when blended with fly ash, paper mill sludge in the form of bark ash can be fed into coal pulverizers and bur ned to produce a concrete addi tive (Collins and Ciesielski, 1994). Wood waste in the form of logging wa ste and sawdust may be further refined and mixed with other recycled materials to impr ove their performance. Loehr and Bowders (2000) for example, combined sawdust with plas tic to form their recy cled plastic piles. “Hard waste” carpet fibers are added in small doses along with a superplasticizer to improve the toughness of concrete (Wang, 1999). The exact dosage or percentage of fibers to add is still under investigation. In another appl ication, very small dosages of carpet fibers are added to soil to form a homogeneous mixture.

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43 Mill tailings are processed through crushing and separation of ore from the impurities either by media separation, gravity separation, froth flot ation, or magnetic separation (Chesner et al., 2002). The key to processing quarry byproducts is blending when they are to be used in base applica tions and dewatering when they are used as mineral fillers (Chesner et al., 2002) Another mineral byproduct material, phosphogypsum is generated from a wet process in which phosphate rock is dissolved in phosphoric acid. Phosphogypsum is the byproduct and when used as a binder, it requires the use of a vibrating powe r screen to create uniform ity (Chesner et al., 2002). Waste glass is crushed and screened to reduce size and densify the final product. This is accomplished primarily by severa l machines including hammermills, rotating breaker bars, breaker plate, and impact crushe rs (Chesner et al., 2002). In addition to these steps, the processed material mu st be inspected for metal and paper. User Interaction In keeping with the relational database model, the remaining sections outline the organization and storage provisions of both application and process data currently available on recycled materials. In addition, the theory behind user interaction with these two data sets is formulated. Application Table An applications table has been created containing eight reco rds corresponding to the eight application categorie s and three fields: Applicat ionName, IDApplication, and ApplicationDescription. The da ta types for these fields are text, autonumber, and memo. Similar to the Materials table, additional app lications may be created in the design view of the Applications table. For example, a user might decide to add a new application called, hydraulic barrier to the table. In this table, I DApplication serves as the automatically incrementing primary key that uni quely identifies each record. Through it,

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44 the data in the Application table is linked dire ctly to the foreign key of the same name in the Process table and indirectly to the rest of the tables. Application Form The setup of the Application forms is similar to that of the Material forms. There are two distinct forms – one for viewing existi ng data and one for adding new data. The user can access them by first clicking on th e appropriate switchboard button. The user can then navigate from the Materials form to the Application form or he may go directly to the Application (Add Entry) form from the second level switchboard. Locks and allowances prevent data editing in existing forms and allow it in the add entry forms. Process Table The process table contains some 57 reco rds that correspond to 57 different ways of refining a recycled material for its intende d application. In the previous section, the processes were described in detail. Although componen ts of different processes sometimes overlap, there exist sufficient distin ctive aspects to warrant their separation. An innovative approach was taken to characte rize, organize, and st ore the processes. Each process was assigned a unique Materia l/Application combination. This serves two purposes: 1) It is practical because material s are processed in certain ways depending on the intended application and 2) It allows th e Process table to serve as a linking table for the many-to-many relationship that exists betw een the Materials tabl e, the Applications table, and the rest of the database tables. Figure 3-2 shows the unique Material/Application combinations th at form each of the 57 processes. IDProcess MaterialName ApplicationName 1 Paper Other 2 Plastics Concrete Additive 3 Plastics Asphalt Pavement 4 Plastics Soil Reinforcement/Stability Figure 3-2: Partial Process Table

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45 5 Incinerator Ash (MSW) Asphalt Pavement 6 Incinerator Ash (MSW) Base/Subbase 7 Scrap Tires Embankment/Fill 8 Scrap Tires Asphalt Pavement 9 Roof Shingles Asphalt Pavement 10 Fly Ash (Coal Ash) Embankment/Fill 11 Fly Ash (Coal Ash) Flowable Fill 12 Fly Ash (Coal Ash) Concrete Additive 13 Fly Ash (Coal Ash) Asphalt Pavement 14 Fly Ash (Coal Ash) Stabilized Base 15 Bottom Ash (Coal) Asphalt Pavement 16 Bottom Ash (Coal) Base/Subbase 17 Bottom Ash (Coal) Stabilized Base 18 Scrubber Base (Coal) Stabilized Base 19 Demolition Debris Embankment/Fill 20 Demolition Debris Asphalt Pavement 21 Demolition Debris Base/Subbase 22 Blast-Furnace Slag Embankment/Fill 23 Blast-Furnace Slag Concrete Additive 24 Blast-Furnace Slag Asphalt Pavement 25 Blast-Furnace Slag Base/Subbase 26 Steel Mill Slag Asphalt Pavement 27 Steel Mill Slag Base/Subbase 28 Non-Ferrous Slag Embankment/Fill 29 Non-Ferrous Slag Asphalt Pavement 30 Non-Ferrous Slag Base/Subbase 31 Cement/Lime Kiln Dust Asphalt Pavement 32 Cement/Lime Kiln Dust Stabilized Base 33 Reclaimed Asphalt Pa vement Embankment/Fill 34 Reclaimed Asphalt Pavement Asphalt Pavement 35 Reclaimed Asphalt Pavement Base/Subbase 36 Reclaimed Concrete Pavement Embankment/Fill 37 Reclaimed Concrete Pavement Concrete Additive 38 Reclaimed Concrete Pavement Base/Subbase 39 Foundry Wastes Flowable Fill 40 Foundry Wastes Asphalt Pavement 41 Paper Mill Sludge Concrete Additive 42 Wood Waste Embankment/Fill 43 Carpet Fibers Soil Reinforcement/Stability 44 Mine Tailings Embankment/Fill 45 Mine Tailings Asphalt Pavement 46 Mine Tailings Base/Subbase Figure 3-2 Continued

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46 47 Phosphogypsum Stabilized Base 48 Quarry Waste Flowable Fill 49 Glass Asphalt Pavement 50 Glass Base/Subbase 51 Plastics Other 52 Paper Mill Sludge Other 53 Foundry Wastes Embankment/Fill 54 Fly Ash (Coal Ash) Base/Subbase 55 Boiler Slag (Coal) Asphalt Pavement 56 Boiler Slag (Coal) Base/Subbase 57 Boiler Slag (Coal) Stabilized Base Figure 3-2 Continued Process Form The Process forms are similar to both the Material and Application Forms. There are two distinct forms – one for viewing existi ng data and one for adding new data. The user can access them by first c licking on the appropriate swit chboard button. He can then navigate from the Materials form to the Applic ation form and then to the Process form or he may go directly to the Process (Add Entry) form from the second level switchboard. Locks and allowances prevent data editing in existing forms and allow it in the add entry forms.

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47 Chapter Four: Engineering and Environmental Properties and Performance Introduction Materials, applications, and processes set the tone for much more detailed data. Engineering properties are included in the databa se for several reasons. First, they more fully characterize how a particular recycled material that is envisioned for a specific application will behave. Obvious ly the attributes that a mate rial exhibits vary not only with different processing mechanisms but also with different researchers. For this reason, it is essential that the database be replet e with as many properties from a breadth of researchers. By considering se veral different studies of the sa me material or process, an exhaustive albeit more rigid interpretation of that material’s “true” behavior surfaces. Another purpose for including prop erties is to add another dimension for searching and sorting. For example, a user can sear ch for a material knowing only its intended application and required abso rption and strength characteristics. In addition to the previously stated reasons, th e inclusion of environmental pr operties allows the user to instantly locate areas of concern. For exam ple, if a processed material has a relatively large concentration of a particular trace meta l, monitoring leachate might be necessary. In addition, quality control as well as source and processing mechanism for that particular material must be emphasized. In short, the properties give the database its detail and robustness. Properties Engineering Properties After reviewing approximately 90 case studies, it was decided that eighteen engineering properties and nine environmental would be selected. The attributes were

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48 chosen both for their ability to comprehensiv ely characterize the materials and for their consistent appearance throughout the literature. Obviously, the list is not all-inclusive. In fact, a provision is included for inputting important supplementary properties such as pH, corrosivity, and other parameters that appe rtain only to certain materials. Again, it must be emphasized that tables can be modi fied by a database designer in order to incorporate more relevant properties. Table 4-1 lists the engineering properties included in the database. Table 4-1: Database E ngineering Properties Property Units Unit weight kg/m2 Specific gravity Shape Size Absorption % Liquid limit Plastic limit Classification Hardness Moh's CBR Cohesion kPa Maximum dry density kg/m3 Internal friction angle degrees Optimum water content % Compressive strength kPa Permeability cm/sec Other properties Omitted Engineering Properties While it is true that these properties accu rately characterize the materials, several other properties are appropriate, and they have not been considered here. Property data must be entered in table format using numbe rs or small phrases of text. Although it is possible that data type ‘OLE obj ect’ can be inserted into a database for the purpose of viewing a figure, such a practice bogs down th e database because of the space the object takes up. Moreover, an OLE object cannot be indexed and is therefore not searchable.

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49 The inclusion of OLE objects goe s against one of the main themes of this relational database: rapid searchability. However, good da ta in the form of grain-size distribution figures, deformation response, and empirical re lationship studies must be sacrificed to achieve it. Perhaps a future effort can build upon the ideas presented in this study and develop a searchable object format that takes up very little of the database space. As it stands though, the user always has the opti on to look into the da ta set or case study further by simply accessing its original reference. Environmental Properties Environmental properties also help to characterize recycled materials and determine their eligibility for use in certain applications and regions. Perhaps even more importantly, environmental properties provide useful data for documenting recycled material use and performance – allowing st ate and federal agencies such as the Department of Environmental Protection (DEP) and the Environmental Protection Agency (EPA) to make informed decisions. Currently, environmental agencies are somewhat reluctant to approve the use of recycled materials without extensive data collection, documented sampling procedures, a nd an array of quality control measures. Often, the materials are prove n to function well from an engineering standpoint, but programs for their implementation become sta lled in the environmental approval stage. With this in mind, the database is equipped w ith ample environmental data from a variety of both laboratory case studies and field case studie s. It is organized into the last four of the nine tables. Table 4-2 contains th e table names and their corresponding fields (excluding the primary keys since they serv e no linking role here but including the foreign keys).

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50 Table 4-2: Environmental Properties Tables Chemical Composition Chemical composition Weight percentage IDCaseProcess Metal Concentration Metal name Concentration (mg/L) Concentration (mg/kg) IDCaseProcess Organic Concentration Organic compound Class Concentration (mg/L) Concentration (mg/kg) IDCaseProcess Leachate Constituent TCLP (mg/L) SPLP (mg/L) EPTox (mg/L) ASTM D-3987 (mg/L) IDCaseProcess Organization and Input In the chemical composition table, a unique IDChemical compound, the primary key of the data table, corresponds to a uni que case study and process combination. For example, a study by Jenkins that examines the use of reclaimed asphalt pavement in base and subbase applications might have severa l chemical compounds and weight percentage values associated with it. The importance of linking this table to both the Performance (case study) table and the Process table is a pparent. Each time a material goes through a refining process to produce a usable mate rial, both engineeri ng and environmental properties have the potential to change. Al so, different researchers have documented varying chemical compounds and weight perc entages of those compounds in their case studies. Therefore, each time data is examin ed from the Chemical Composition table, the

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51 user is aware that the information is specific to one particular researcher and one particular process. Not surprisingly, over 500 re cords currently exist in this table. The Metal Concentration table has one ma in purpose – to identify and quantify the existence of trace metals within a pro cessed material. Similar to the Chemical Composition table, it is linked to both the Pe rformance table and the Process table. Therefore, data in this tabl e corresponds to a unique case study and processed material. For example, scrap tires envisioned and pro cessed for use as embankment or fill in a study by a particular researcher might include concentrations of aluminum, lead, and any other metal. The presence of certain metals in high concentrations precludes their use in several applications. Both national and state recommended allowable limits (RALs) exist for these materials. In add ition, local drinking water standa rds specify acceptable limits from both health and aesthetics criterion. Table 4-3 summarizes environmental concerns of waste and recycled materials. Many of these concerns are ad dressed through data collection in the database. Table 4-3: Properties of Envi ronmental Concern (Kim, 2003) Parameter Potential Hazardous Property Affected Leachable trace metals As, Cd, Cu, Cr, Hg, Pb, Zn Ground/surface water Leachable organics Benzenes, phenols, corrosivity, pH Ground/surface water Soluble solids Soluble and mobile salts Groundwater Total respirable dust Respirable fine particles Air Trace metals in dust Respirable or deposited trace metals Air/secondary Trace organics in dust Respirable or deposited trace organics Air/secondary Volatile metals As, Hg, Cd, Pb, Zn re leased at high temp. Worker health Volatile organics Chlorinated hydrocarbons released Worker health The Organic Concentration table is mainly concerned with the presence of various classes of organic compounds (i.e. volatiles, semi-volatile s, phenols etc.) that are components of processed recycl ed materials. Sp ecial areas of concern include organic compounds such as benzenes, phenols, and viny l chloride that impact both groundwater and surface water quality (Chesner et al., 2002). Each record in the database corresponds to a specific case study and process. A study by Freeman, which analyzes the suitability of fly ash as flowable fill might have anywhere from ten to thirty entries for organic compounds and their concentr ation values in mg/L.

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52 The final environmental properties table, Leachate, warrants special consideration as there are several different tests used to measure this parameter. Many of these tests developed as a result of the Resource Conservation and Recovery Act (RCRA) that was passed by Congress in 1976. It dealt with h azardous waste disposal and environmental management of waste. These tests f it into one category of leachate tests: regulatory methods The other two categories are standard methods such as those specified by organizations including ASTM and research methods developed to measure specific and unique properties (Kim, 2003). Leaching is defined as the removal of materials by dissolving them away from solids. All four tests included as part of the database are batch tests – tests involving a given volume of leachant solution such as water for a given period of exposure time. The four test s are summarized in the Table 4-4. Table 4-4: Regulatory Me thods Tests (Kim, 2003) Method Leachant Sample size (g) pH L/S Units Time (hr) TCLP Acetic acid or acetate buffer 100 2.88 20 mg/L 18 SPLP Water w/ nitric and sulfuric acid 100 4.2 20 mg/L 18 EPTox Water 100 5.0 20 mg/L 24 ASTM Water 70 20 mg/kg 18 Unrelated to the fundamental questions ra ised by this thesis, a completely singular research thread has developed around the comparison of these tests in terms of reproducibility and accuracy as compared to some standard “true value.” “With exact duplication of regulatory or standard methods, there is a 60 to 80 perc ent probability that tests conducted by different labor atories with the same protocol will have comparable results” (Kim, 2003). The purpose of the databa se is to organize and present data rather than interpret or promote particular methodologies. Table 4-4 also provides the truncated abbreviations of the regulatory leaching batch tests. The full names are as follows: Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), Extraction Procedure Toxicity Test (EPTox), and Standard Test Method for Shake Extraction of Solid Waste with Water (ASTM-D3987). In addition to th e differences shown in the table among the tests, TCLP and SPLP warrant further explanat ion. TCLP is an EPA analytical method

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53 designed to simulate sanitary landfill cont aminant leaching (Aerotech, 2004). Its main purpose is to characterize a wa ste material as hazardous or non-hazardous. SPLP, on the other hand, is an EPA analytical method de signed to simulate acid rain effects. Specifically, it is concerned with toxic orga nic and inorganic soil contaminants that migrate into the groundwater table (Aerotech, 2004). Data Range Some research studies are numerically and test-intensive. A study may contain data from the testing of twenty materials with only a few samples from each material or it may contain data from testing only one material with twenty samples. In either case, a decision must be made as to which data s hould be entered into the database. For engineering properties, each pa rameter is assigned two fields, high and low, so that a high and low value from that particular study can be recorded. Thus, rather than a collection of isolated information from tests, the databa se contains a data ra nge. Certainly some element of subjectivity must ente r into the database design stage and the da ta entry stage. In both engineering and environmental test ing, statistical outlier s are discarded. Although it is possible that thes e outliers represent valid data in most instances, such data is usually the result of contaminated samples a nd/or poor testing protocol. Environmental tests do not include provision s for entering a data range. Instead, an average value is calculated from each te sting category after discarding the outliers. For example, a TCLP test performed ten ti mes for one processed material may include one result that is significantly removed from the other nine values. As a result, the average is recorded for the nine values and then entered into the database. Evaluating Performance An exhaustive review of current and past research on recycled materials was conducted in an attempt to fill the database with as much useful information as possible. It is obviously impossible to completely characterize each material in this document.

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54 However, a limited review of the materials is de finitely appropriate. In the sections that follow, some of the materials are examined in detail and a discussion of general performance, field use, limitations, and special considerations are al so included. Perhaps this section can be viewed as a sort of comparison and summary of findings. Plastics Surprisingly, out of the three previ ous efforts at a recycled materials comprehensive compendium, only one included any information on plastics. This is probably due to the fact that it is a relativ ely new material in th e arena of geotechnical and transportation applications. As stated ea rlier, plastics are used in at least two stabilizing mechanisms: discre te and homogenous. Consoli et al. (2002) examine sand reinforced with strips of recycled, processed, plastic strips. Long, fl at strips of varying length are added either alone or in combina tion with Portland cement in small doses to increase strength and stiffness of loose sand. The plastic strips improved both peak and ultimate strength in both cases (Cosoli et al., 2002). The plastic waste exhibited the following engineering properties: specific gravity of 1.06, inte rnal friction angle between 37 and 43, tensile strength between 207 and 230 MN/m2, and elastic modulus of 7 GN/m2 (Cosoli et al., 2002). Loehr and Bowder s (2000) explore weak reinforcement of slopes with recycled plastic pi les. In the field study, 317 of the piles are eventually installed with a continuous monitoring system so far proving the plastic piles’ efficacy (Loehr and Bowders, 2000). Compressive stre ngths of 21000 kPa and tensile strengths of 13000 kPa were achieved with a co st of $42 per square meter of slope face (Loehr and Bowders, 2000). So far, it appears that plas tics are used in only a few applications – slope stability and soil reinforcement. To be used properly it is important to specify the type of plastic (i.e. PET fibers or HDPE pellets etc.). In addition, very little environmental data is available on this material.

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55 Incinerator Ash Incinerator ash has been used in as phalt concrete and in base and subbase applications. It has been used in Chi cago, Houston, Washington, D.C., and Harrisburg, Pennsylvania, and Lynn, Massachusetts – all in asphalt pavement applications and most as a replacement for coarse aggregate in asphalt paving mixes (Collins and Ciesielski, 1994). Concerns have been raised over l eaching of heavy metal such as lead and cadmium since past efforts have seen amounts in excess of regulatory limits (Collins and Ciesielski, 1994). In general, EPA has been slow to a pprove incinerator ash as a construction material, and has even characterized it as a borderline hazardous waste in some instances. Many of these problems st em from the inconsistency of the processed material itself. The material may be processe d in a mass burn facility (no presorting) or a refuse derived-fuel facility (r equires presorting), and this fac ility may be new or old. As a result, the quality of the final processed ash is inconsistent and may exhibit varying engineering and environmental properties (Chesner et al., 2002). It is recommended that this material be used under a controlled process and environmental monitoring. Fortunately, engineering properties of incinerator ash are less scattered: unit weight of 965 to 1290 kg/m3, specific gravity of 1.86 to 2.24, CB R of 75 to 150, friction angle of 40 to 45, abrasion of 44 to 50%, absorptio n of 3.6 to 14.8%, and maximum dry density of 1730 kg/m3. Scrap Tires Scrap tires have easily generated the most recent research interest for their wideavailability, potential applica tions, consistent engineering properties, and relatively lowimpact environmental properties. Although the use of scrap tires in field projects has been widespread with some 40 state highway agencies conducting some sort of research, its use is still deemed experimental (Collins a nd Ciesielski, 1994). This is due to several factors including high upfront costs (investment in processing machines, monitoring equipment etc.), the necessity of monitori ng performance and maintenance requirements

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56 over a long period of time, and the evol ving mandates and environmental guidelines involving the use of scrap tires. Tire ch ips have been investigated for use in embankments and fill (Bosscher et al., 1997; Humphrey et al., 1998; Vipulanandan and Basheer, 1998) in asphalt pavement applicat ions (Chesner et al 2002), in specialty applications (Reid et al, 1998) and their impact on the environment has been assessed (Chesner et al, 1998; O’Shaughnessy and Garg a, 2000; Liu et al., 2000). The following range of engineering proper ties has been observed for scrap tires : unit weight of 390 to 584 kg/m3 depending on void ratio, specific gravity of 1.1 to 1.3, absorption of 2 to 3.8%, cohesion of 8 to 12 kPa, internal friction of 19 to 41 (dependent on whether shreds, chips, or crumb rubber is used), permeability of 1.5 to 15 cm/sec, heating value of 28000 to 35000 kJ/kg, and Young’s modulus of 770 to 1250 kPa. The reasons for the relatively wide ranges of properties stem from the use of varying sizes and shapes of scrap tires. In general, crumb rubber, the sm allest processed scrap tire material, has a higher unit weight, higher friction, and lower permeability precisely because ther e is less void space. The large variation in processing techniques and m achinery has been addressed in a previous section. However, two environmen tal studies warrant sp ecial consideration. O’Shaughnessy and Garga (2000) examined the leaching behavior of an embankment constructed with scrap tires. The researc h, a combination field and laboratory study, found almost no evidence of eith er metals or organics exceed ing local regulatory limits. Some “anomalies” existed including the presen ce of selenium in concentrations that slightly exceeded limits and inconsistenc ies in long-term results associated with concentrations of lead, cadmium, and ch romium (O’Shaughnessy and Garga, 2000). However, the difficulty is in sorting and comp aring such results to similar studies that cite conflicting data. It appears that more environm ental data is required. A study by Liu et al. (2000) also evaluated the environm ental characteristics of scrap tire embankments through an original effo rt and comparison with previous studies. The study found that the control sample, t ypical bituminous asphalt actually leached higher concentrations of metals than the samp le containing scrap tires (Liu et al., 2000). In addition, none of the labo ratory samples containing scra p tires exceeded allowable

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57 limits for TCLP tests and EPTox tests (Liu et al., 2000). Table 45 summarizes their findings. Table 4-5: Scrap Tire Leachate Summary in mg/L (Liu et al., 2000) Metal Minn. pH 3.5 Minn. pH 5 Minn. pH 7 Minn. pH 8 Wisconsin AFS Tire Mgmt. Council VDOT, long-term Al 0.746 As ND Ba 0.488 0.205 0.174 0.265 0.12 0.59 2.08 Cd 0.125 0.007 0.005 0.005 ND 0.004 Cr 0.235 0.002 0.005 0.002 0.003 0.05 0.082 Cu 0.328 Fe 500 41.2 0.531 0.718 0.23 31.62 Pd 0.417 0.051 0.038 0.039 0.015 0.016 0.138 Mn 0.3 Hg 0.0004 Ni 2.46 Se 0.203 0.054 0.045 0.028 0.005 ND Ag 0.005 Zn 23.5 17.5 3.38 0.005 0.63 0.153 Scrap tire field implementations have ga ined notoriety for recent failures and therefore warrant special consideration. In 1995, two scrap tire road embankments in Washington State and one in Colorado began to exhibit signs of exothermic reactions – heat is released as a result of chemical or biochemical reac tions (Liu et al., 2000). This led researchers to examine the causes and pr opose solutions. All three of the field embankments/fills were constructed exclusively with scrap tires, and the tire shreds had exposed steel belts (O’Shaughnessy and Garga, 2000). According to researchers, “the potential causes of initial exothermic reaction are oxida tion of exposed steel wires, oxidation of rubber, microbes consuming e xposed steel wires or generating acidic conditions, and microbes consuming liqui d petroleum products” (O’Shaughnessy and Garga, 2000). The existence of free oxygen wa s a result of inadequa te soil cover or exposure to fertilizer-rich so il or crumb rubber. As a re sult of these experiences, guidelines for embankment construction using scrap tires are now available.

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58 Roof Shingles As a material that has been studied much less than some of the others, recycled roof shingles could prove its value if certain limitations can be addressed. As stated in the materials section, two types of roofi ng shingle byproduct exist: prompt roofing shingle scrap (leftover from the manufacturing of roof shingles) and tear-off roof shingles (leftover from replacement of roofs by contractors). Both the engineering and environmental properties of prompt roofing shingle scrap are fair ly consistent, which facilitates their incorporation into civil engi neering applications. However, tear-off roof shingles may contain deleterious material s such as “nails, felt underlayment, metal flashings, wood, and water proofing and insulati on materials” (Chesner et al., 2002). In addition, the asphalt cement binder component of this type of scrap is usually old and weathered. A final environmental concern come s from the existence of asbestos fibers, which present a serious health ri sk, in older shingles. The im portant consideration here is that if recycled roof shingles are to be used, the source must be controlled. Whether this happens through the exclusive use of prompt roofing shingle scra p or if it happens through presorting and control on th e part of the material supp lier/recycler, the issue must be addressed. Field implementa tion has occurred mainly in the form of cold-patching of antiquated pavement sections in low tr affic areas (Collins and Ciesielski, 1994). Coal Byproducts (Fly Ash, Bottom Ash, Boiler Slag) The various forms of coal ash have been studied extensively: fly ash (Vipulanandan and Basheer, 1998; Vipulanan dan et al., 1998; Tand on and Picornell, 1998; Senadheera et al., 1998, Collins and Ciesiels ki, 1994; Chesner et al, 1998; Chesner et al., 2002). Fly ash can be used as in asphalt pavement, as flowable fill, as a concrete additive, and in stabilized ba ses or embankments. Due to its pozzolanic properties, or tendency to form cementitious compounds, when combined with calcium and water, it can be adapted to various conditions (Collins and Ciesielski, 1994). Also, it is an abundant recycled material, but only a small percen tage is actually put to use. In general,

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59 fly ash has proven to be a versa tile material, and it has perfor med well is the vast majority of these applications. However, as has been mentioned in a previous section, the class and quality of fly ash varies. Depending on th e type of parent coal (bituminous, subbituminous, and lignite) that is burned, th e class (Class-C or Class-F), and other processing mechanisms and technology, the properties of fly as h, especially the environmental ones can vary dramaticall y. The range of both engineering and environmental properties is too great to in clude here, but it can be accessed using the database. Bottom ash and boiler slag are generally not investigated indi vidually, but rather they are included as part of comprehensive studies (Collins and Ciesielski, 1994; Chesner et al., 1998; Chesner et al., 2002). Unlik e fly ash, these materials do not exhibit pozzolanic properties, but they can still be used in asphalt pavement, base, subbase, and stabilized base applic ations. Like fly ash, the engin eering and environmental properties vary with the type of parent coal as well as the processing technique. An element of concern is the possible corrosive properties of these materials as a result of the salt content and low pH of both bottom ash and boi ler slag (Chesner et al., 2002). Corrosion potential should be investigated prior to use. The followi ng engineering properties were observed: unit weight of 720 to 1620 kg/m3, specific gravity of 2.1 to 2.89, absorption of 0.8 to 7.52%, CBR of 36 to 70, internal friction of 34 to 55, permeability of 0.001 to 0.1 cm/sec, abrasion of 35 to 43%, and void ration of 0.49 to 0.53. The high range of values suggests the necessity of material testing prior to use or source control. Scrubber Base Flue gas desulfurization (F GD) sludge, or scrubber base has been investigated for potential use in stabilized base and embank ment applications (Chesner et al., 1998; Chesner et al., 2002). Field implementa tion has taken place in Kentucky and Pennsylvania sites (embankments), Louisian a (road shoulders), a nd Texas (stabilized base) (Collins and Ciesielski, 1994 ). It is important to di fferentiate between different forms of FGD scrubber base. The product may be in an unoxidized calcium sulfite form,

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60 which can be used for roads or it may be in an oxidized calcium sulfate form, which can be used as a concrete additive (Chesner et al., 2002). In its unoxidized state, FGD scrubber can be further subdivided by whethe r it has been dewate red, stabilized, or fixated. Not surprisingly, engineer ing properties are widely scattered. Demolition Debris Investigated for its use in asphalt pavement and base/subbase applications, demolition debris provides another interesting al beit inconsistent recycled material. The material is an amalgamation of wood, plaster, concrete, glass, metal, brick, shingles, and asphalt (Collins and Ciesielski, 1994). Becau se of the variation in both quality and percentage of these components and because the components themselves were manufactured differently, it is difficult to control the material to meet gradation or construction performance requirements. Ag ain, the quality control responsibility must either lie with the state agency that will be using the material or with the material provider such as the manufacturer or the recycl ing facility. The existence of both sewage sludge and asbestos is a very real possibility that must be investigated prior to incorporation into road applicati ons (Collins and Ciesielski, 1994). Slags (Blast-furnace, Steel-mill, Non-ferrous) Historically, it has been difficult to gather accurate inform ation on the various types of slags. Researchers have often failed to divide the slags into subcategories before summarizing data. In additi on, non-ferrous slags are almo st always grouped into one category even though they exhibit very different properties based on their parent ore (i.e. copper, nickel, zinc, phosphorus, lead etc.). Blast-furnace slag can be air-cooled, granulated, or expanded, and it can be used in asphalt pavement, base, embankments, or as a concrete additive (Collins and Ciesiels ki, 1994). Steel slags are produced from one of three types of furnaces: open hearth, basic oxygen, and electric arc and can be used in asphalt or base applications (Chesner et al., 2002; Coll ins and Ciesielski, 1994). In

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61 general, these slags are heavier than traditi onal aggregate materials, and they are hard, stable, and resistant to abrasion (Collins and Ciesielski, 1994). These materials have been used for several years despite two draw backs. First, mixing the materials provides an inconsistent product. S econd, leachate from sl ag fills has sometim es clogged drains (Collins and Ciesielski, 1994). Used in asphalt pavement, embankment, and base applications, non-ferrous slags exhibit varyi ng properties according to their parent ore and whether they have been air-cooled or granulated (Collins and Ciesielski, 1994). Their use has been limited relative to the ot her types of slag. The following engineering properties have been observed for blast-furnace slags : unit weight of 800 to 1940 kg/m3, specific gravity of 2 to 2.7, absorption of 1 to 6%, hardness of 5.5 to 6, CBR of 250, internal friction 40 to 45, and abrasion of 40%. Steel-mill slags : unit weight of 1600 to 1920 kg/m3, specific gravity of 3.2 to 3.6, absorpti on of 3%, hardness of 7, CBR of 300, internal friction 40 to 50, and abrasion of 23%, pH above 11 cont ributes to corrosive properties. Non-ferrous slags: unit weight of 1360 to 3800 kg/m3, specific gravity of 2.8 to 3.8, absorption of 0.13 to 5%, hardness of 7, internal friction 40 to 53, and abrasion of 26%. Kiln Dusts (Cement and Lime) Kiln dusts have been investigated essentially from a field implementation standpoint (Collins and Ciesielski, 1994). Un fortunately, they have performed poorly. The principal uses are in aspha lt pavement and stabilized base applications (Chesner et al., 2002). In addition to the poor performance of these materials, there is some question as to the underlying processing mechanism. Specifically, cement kilns burn hazardous waste as fuel sources, and this must be addr essed either to testing or monitoring before kiln dusts can be used in practice. In shor t, this material does not appear to be very promising.

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62 Reclaimed Asphalt Pavement and Reclaimed Concrete Pavement Reclaimed asphalt pavement has been inve stigated for use in hot and cold mix asphalt pavement as well as base, stabilized base, and embankment applications. The research is clear that reuse of this materi al is approaching 100 pe rcent, and the portion that goes unused each year is usually stockpi led and used the following year (Collins and Ciesielski, 1994; Chesner et al., 2002). Every state is recycling asphalt pavement in some capacity. Performance and implementation prog rams have followed suit, and as a result processing capabilities are well-developed. One problem w ith RAP is its inconsistency. Specifically, RAP is a product of constitu ent materials such as asphalt type, and stockpiles can often be contaminated with fo reign soils and debris. Also, the parent pavements themselves vary in quality depending on how many times they were resurfaced or patched (Chesner et al., 2002). So it is that quality control must be maintained preferably at a local level to en sure uniformity in material properties. The following engineering properties were observed for reclaimed asphalt pavement : unit weight of 1600 to 2300 kg/m3, CBR of 20 to 150, maximum dry density of 1872 to 2000 kg/m3, and optimum water content of 5 to 8%. The large range in CBR is generally attributed to reasons mentioned above. Reclaimed concrete pavement does not enjoy the same widespread use as reclaimed asphalt pavement. However, the potential for a higher quality product is definitely there. Reclaimed concrete pavement (material), or RCM, is used as a concrete additive and in base and emba nkment applications (Chesner et al., 2002). As is the case with other materials, RCM will produce consistent properties if it is well-processed and it comes from a consistent source. Problems aris e from the use of recycled concrete from various sources. Aggregates from the concrete in footings and pile s can contain foreign substances as compared to pavement concre te (Chesner et al., 2002). Also, different concrete types yield a product that has vary ing aggregate quality, size, and compressive strength. “Precast concrete generally has a smaller aggregate size, higher compressive strength, and less variation in strength and other properties than cast-in-place concrete” (Chesner et al., 2002). Finally, salty environments such as Fl orida ensure exposure of the

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63 parent concrete to high levels of chlorides. The following properties have been observed for reclaimed concrete pavement : specific gravity of 2 to 2.5, absorption of 4 to 8%, CBR of 94 to 148, maximum dry density of 1984 kg/m3, internal friction of 40, and optimum water content of 7.5%. Foundry Waste Foundry waste has been used in asphalt pavement applications and flowable fill. Edil and Benson (1998) and Abicho u et al. (1998) investigat ed the use of waste foundry sand as hydraulic fill. The presence of up to 15% bentonite reduces the hydraulic conductivity dramatically (Edil and Bens on, 1998). Additionally, waste foundry sand performed satisfactorily when it was used to construct embank ments (Mast and Fox, 1998). Foundry waste incorporates furnace dust, arc furnace dust, and residue in addition to foundry sand. Special consideration must be given to the presence of large concentrations of trace metals in foundry dusts (Collins and Ciesielski, 1994). Foundry sand is a better alternative due to its greater availability a nd its status as a non-hazardous material. Even so, attention must be paid to contaminants such as stone and trash as well as to its fine, uniform gradation and leachi ng of some heavy metals and phenols (Collins and Ciesielski, 1994; Chesner et al., 2002) Depending on the foundry source, high concentrations of cadmium, lead, copper, nick el, and zinc are also possible (Chesner et al., 2002). The following engineeri ng properties were observed for foundry waste : unit weight of 2590 kg/m3, specific gravity of 2.39 to 2.6, absorption of 0.42 to 0.46%, liquid limit of 31, plastic limit of 25, CBR of 4 to 20, cohesion of 7 to 15 kPa, maximum dry density of 1855 kg/m3, internal friction of 33 to 40 water content of 0.1 to 10%. Paper Mill Sludge Very little information is available on paper mill sludge alth ough it has been cited in the literature as a covering for landfills (Quiroz and Zimmie, 1998). Its use was tested as a substitute for traditional landfill cover mate rials such as clays. It exhibits unique

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64 properties such as high water contents, high organic contents, low shear strengths, and high compressibility (Quiroz and Zimmie, 1998) Hydraulic conductivity is the design parameter of interest, and it is this value that decreases while shear strength increases as the material consolidates. To ensure smoot h construction, low pressure equipment must be used to place and comp act the sludge (Quiroz and Zi mmie, 1998). In addition, researchers have pointed to the need to es tablish some mechanism of quality assurance since the paper mill sludge byproduct is se nsitive to both paper production changes and changes in wastewater treatment proce sses (Quiroz and Zimmie, 1998). Another byproduct of the paper industry, spent sulf ite liquor may have potential for soil stabilization. Perhaps this is a new materi al that warrants further investigation. The following engineering properties were observed for paper mill sludge : specific gravity of 1.88 to 1.96, liquid limit of 285, plastic li mit of 94, compression index of 1.24, and extremely low permeability values (typically less than 10-8 cm/s). Carpet Fibers In general, carpet fibers performed inadequately when used for soil stabilization. They performed better as conc rete reinforcement when added is doses of 2 percent (Collins and Ciesielski, 1994). However, impr ovement in flexural strength and toughness came at the expense of compressive strength. As soil reinforcement, carpet fibers are impractical especially in sa ndy soils where they tend to mi grate to the surface (Wang, 1999). Also, even when mixed in concrete, a superplasticizer is required to increase workability to an acceptable level (Wang, 1999). Researchers have had bad experiences with carpet fibers, and their poor engineer ing properties and limite d availability make them an undesirable recycled material. The following engineer ing properties were observed for carpet fibers : unit weight of 1724 kg/m3, optimum water content of 16.5%.

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65 Mill Tailings In relation to many of the materials, m ill tailings are extraordinarily abundant. As fine-grained waste from ore concentration pr ocesses, mill tailings are produced from the concentration of copper, ir on, taconite, lead, zinc, and uranium ores (Collins and Ciesielski, 1994). They have been used in asphalt pavement, base /subbase applications, and as embankment and fill materials. Unfortunately, properties, especially grain-size distribution vary dramatically with methods of ore processing, percentage of solids in the slurry, and location of the material within the same tailing pond (Collins and Ciesielski, 1994). Other problems include “fineness, high impurity content, tr ace metal leachability, propensity for acid generation, and/or remote location” (Chesner et al., 2002). In addition, tailings from gold may contain cyanid e, those from uranium may be radioactive, those from sulfide ores may contain arseni c, and those from taconite may contain asbestos (Chesner et al., 2002). The follo wing engineering propert ies were observed for mill tailings : unit weight of 1600 to 2300 kg/m3, specific gravity of 2.6 to 3.5, maximum dry density of 2025 kg/m3, internal friction of 28 to 45 optimum water content of 10 to 18%, permeability of 0.01 to 0.0001 cm/sec. Phosphogypsum Phosphogypsum is a controversial material that has been investigated extensively in the past but is currently only cited in passing (Chesner et al, 1998; Chesner et al., 2002). As a local material, phosphogypsum st acks can be found almo st exclusively in Florida. However, due to a 1989 EPA ban on the use of phosphogypsum, research has slowed dramatically (Collins and Ciesielski, 1994) As a result, special petitions must be made to EPA before this material can be us ed or researched (Che sner et al., 2002). Despite all this, experimental sections of phosphogypsum stabilized roads are still performing well in Florida and Texas (Collins and Ciesielski, 1994). Most construction difficulties were a result of excessive mois ture, overstabilization, and poor mixing and sealing (Chesner et al., 2001). The futu re of phosphogypsum as a viable recycled material is in limbo. The following engi neering properties were observed for

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66 phosphogypsum : unit weight of 1470 to 1670 kg/m3, specific gravity of 2.3 to 2.5, cohesion of 76 to 179 kPa, maximum dry density of 1670 kg/m3, internal friction of 28 to 47, optimum water content of 13 to 18% variable compressive strength, and a relatively high permeability. Quarry Waste Quarry waste consists of screenings, settling pond fines, and baghouse fines, and they have been used as cement additives, and in asphalt pavement and flowable fill (Chesner et al., 2002). It is widely availabl e and has been used in Arkansas, Florida, Georgia, Illinois, Missouri, and Vermont (Collins and Cies ielski, 1994). Consideration must be made to completely dewater the waste after reclamation and prior to use. In addition, researchers must be conscious of the va riation in material properties that are the results of different aggregat e types and producer sources (C ollins and Ciesielski, 1994). Local officials can be assured of consistent engineering and environmental quarries only within the same quarry location. Waste Glass Waste glass was investigated for use in asphalt pavement, base, and embankment applications (Chesner et al., 2002; Collins a nd Ciesielski, 1994). Most glass recycling occurs through individual household sorting befo re it goes to material recovery facilities to further separate and grind it down. Atte ntion is given to speci fications that limit impurities such as ceramics, ferrous metal, paper, plastics etc. (Chesner et al., 2002). Such impurities negate the otherwise uniform properties that clean glass exhibits. The finished product can be pro cessed to decrease both size an d angularity make it suitable for additional applications. The following engineering properties were observed for waste glass : unit weight of 1120 to 1900 kg/m3, specific gravity of 1.96 to 2.52, hardness of 6, CBR of 42 to 132, maximum dry density of 1900 kg/m3, internal friction of 51 to

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67 53, optimum water content of 5.7 to 7.5% permeability of 0.06 to 0.2 cm/sec, and abrasion of 36%.

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68 Chapter Five: Database Design As was mentioned previously, before proceeding with the database design, a literature review was conducted to establish the recycled material research that had already been accomplished. Relevant sources of research including technical reports, archived publications, onlin e resources, books, special p ublications, and conference proceedings were categorized and documented. This step served the dual purposes of supplying substance for the database and highli ghting areas in need of further research. A commercially available software, Microsoft Access, was used as the database management system (DBMS). Identification of Tables and Fields Although table organization and corresponding field headings are assigned at the discretion of the database designer, certain obvious choices exist. There is a table dedicated to the 24 recycled materials as well as one for their potenti al applications and one for the processing mechanisms and techni ques that generate a usable product. In addition, tables exist for each of the followi ng: performance (case study), case/process (engineering properties), chemical composition, metallic concentration, organic concentration, and leachate analysis. Some tables such as the Performance table serve as intermediate tables – linking the primar y tables while simultaneously providing compulsory information, which in this case includes authors names, literature reference, and the state and year in which the research was performed. The Materials table contains fields corresponding to the material’s name, description, and availabi lity. Consistent with each of the nine tables, there exists a field, IDMaterial, which is a unique numerical identifier, or primary key, to be used when generating relationships among tables. As me ntioned previously, the primary key or ID

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69 is data type “autonumber,” which increments automatically each time a new record is created. Each primary key field corresponds to at least one field of similar name that functions as a secondary or foreign key. Prim ary and foreign keys directly link two data tables together and indirectly link the entire set of tables into one continuous, organized compendium. In addition, the key fields es tablish the requisite relationships between tables and fields. A portion of the Mate rial table is repr oduced in Figure 5-1. Figure 5-1: Part of the Material Table

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70 The Application table is composed of appl ication titles and th eir descriptions. Like the Materials table, it ha s a primary key, IDApplication, wh ich links it to the rest of the database. The Process table contains one primary key, IDProcess, and two foreign keys: IDMaterial and IDApplicat ion in addition to a process description field and a cost per ton field. The IDProcess automatica lly increments each time a new, unique material/application combination is entered. The Performance tabl e has one primary key, IDCaseStudy that uniquely identifies each ca se study and one foreign key, IDProcess. This table contains requisite fields to comprehensively ci te each case study: Authors, Reference, Year, State, a nd a brief SummaryMemo that summarizes the purpose and findings of the research effort. The Case /Process table contains one primary key, IDCaseProcess that identifies each unique comb ination of a specific process (material and application combination) and a specific cas e study. It also contains two foreign keys: IDProcess and IDCaseStudy. Th is table also encompasses eighteen fields corresponding to eighteen engineering properties. The majori ty of engineering properties have a “high” field and a “low” field – allowi ng the user to enter a range of data values. The Chemical Composition table contains a chemical co mpound name, a foreign key (IDCaseProcess), and a field in which to cite the chemical compound’s weight percentage. Similarly, the Metal Concentration ta ble, the Organic Concentration table, and the Leachate table all share the same foreign key, IDCaseProcess. However, the Organic Concentration table also has fields for class (i.e volatiles, semivolatiles etc.) and organic concentration listed in two different measurement units. The L eachate table summarizes data from four regulatory batch tests – TCLP SPLP, EPTox, and ASTM D-3987. Developing Data Relationships Choosing a relational database model ove r a network or hierarchical model ensures that any two tables interact accordi ng to four general relationships: one-to-one, one-to-many, many-to-many, or no relation. Th is step is crucial because it directly affects the data that can be accessed and view ed by the user. In addition, relationships

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71 among data that exist in real life must be carried over into the database to ensure practicality. Proper relationshi ps mitigate data redundancy and poor user access to data. Table Relationships A one-to-many relationship exists between the Material and Pr ocess tables and between the Application and Process tables. Th e first signifies that each material can be processed in one or more ways before it is us ed as an engineering material. For example, scrap tires can be shredded to a particular size before compaction or the process can involve a series of shredding, steel belt removal through magnetic separation, and grinding to meet crumb rubber specifications However, each process has one and only one material associated with it. As anothe r example, recycled plastic, an element from the Materials table, can be pr ocessed into composite recycled plastic piles/lumber or it can be cut into small strips before it is in corporated into geotechnical systems. The difficulty is in developing the processing mech anisms so that they are specific enough to avoid overlap with other materials and yet ge neral enough to ensure practicality. This is more of an issue with the pr ocess description field that is included in memo format. Concerning applications, the one-to-many re lationship means that each of the eight applications (i.e. embankment/fill, asphalt pavement, flowable fill etc.) can be associated with more than one process. To employ a ma terial as an asphalt modifier, it may be reclaimed, crushed, and screened or it may be mechanically combined into pellet form. Each process is associated with only one applic ation. So it is that for the purposes of the database, each process is actually a unique co mbination of a material and an application, and the process table links the other two while establishing the many-to-many relationship between them. E ach of the materials can be used in one or several applications and each application can be fulfilled by one or more materials. The Process table is paramount. Besides linking the aforementioned tables, it also has a many-to-many relationship with the Perfor mance or case study table. Each process, or unique material/application combination is do cumented by one or several case studies, and each case study may contain information re lating to several processes. For example,

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72 a particular study may document the use of r oof shingles and bottom ash in stabilized base applications. Roof shi ngles and bottom ash in embankments may also be at least part of the research of a different st udy. The linking table between Process and Performance (case study) is the aptly named Case/Process table; it contains the engineering and environmental parameters required to completely characterize the material. This table contains a vast amount of data. For exam ple, a single r ecord in this table might contain all the engineering data documented by a single study on kiln dust used as road base. The final four tables, Chemical Com position, Metal Concentration, Organic Concentration, and Leachate ar e the environmental properties tables. They are connected to the rest of the database through a one-to-many relati onship with the Case/Process table. Again, for a single material envisi oned for single application, documented in a single case study, there exist several chem ical compounds with corresponding weight percentages. This re lationship carries through to the presence of several trace metals, several organic compounds, and several leachate test results – all for a single case/process combination. Refer to Figure 1-4 from Chap ter 1, which shows the database schema. Each table name is placed at the top in bold and each primary key is underlined. The lines delineate relationships among the tables with the ‘1’ and ‘ ’ representing the ‘one’ and ‘many’ relationships, respectively. Content Overview A more detailed examination of table head ings and their corresponding fields is useful to understand how and where the data is inputted. Only th e primary tables and those linking tables that c ontain important parameters ar e included in this discussion. Material Table Thorough review of the literat ure revealed 24 recycled ma terials suitable for this table. Although not encompassi ng every recycled material currently studied, these 24

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73 provide a satisfactory, representative sample about which there is sufficient research. The materials belong to one of three cate gories based on their origin. Collins and Ciesielski (1994) identified th ese categories as domestic wast e materials, industrial waste materials, and mineral waste materials. Applications Table This table displays eight applications – how the materials functions as part of a highway or geotechnical system. The applic ations are as follows: embankment/fill, flowable fill, concrete a dditive, asphalt pavement, base/subbase, stabilized base, soil reinforcement/stability, and other. Typical ly, embankment/fill applications involve raising a roadway with compacted material providing a bridge approach, or similar activities. Select fill or ot her soil is usually used but can be mixed with or completely supplanted by aggregate-like recycled materials. Flowable fill, a self-cementing slurry, is generally used as excess fill in hard to reach areas such as near utilities and pipes. Recycled materials can be us ed in place of its component s – either as aggregate or cementitious material. As concrete additives, recycled materials function as mineral admixtures that improve the strength, workab ility, and resistance to sulfates of the concrete. These materials are also used as substitute aggregate and/or mineral filler in asphalt pavement applications. In base and subbase applications, recycl ed materials take the place of aggregate materials and cementing materials, and they function as a load transfer mechanism between overlying pavement and the soil undern eath. Used in stabilized base, recycled materials take the place of aggregates if th e latter is unavailable and may improve the self-cementing properties of the stabilized base. Soil reinforcem ent/stability is really two sub-applications. The first involves mixing a marginal soil with doses of a recycled material that improves the mechanical prope rties of the soil. The second refers to stabilizing slopes with discrete elements such as recycled plastic piles. The “other” category exists for aesthetic applications, very specialized applicati ons, or those that do not involve transportation or geotechnical criteria.

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74 Process Table In addition to the aforementioned primar y keys and linking fields, the process table is also composed of a description for each of the over 50 material/application combinations. Although each process is uni que, many of the same actions are performed on the materials. These include shreddi ng, screening, reclaiming, crushing, dewatering, stockpiling, and removing contaminant debris. Besides modifying them chemically, the recycled materials are often blended with other aggregate or fill to ensure uniformity or to meet gradation requirements. To process roof shingles that are to be used in asphalt pavement for example, debris must first be removed. Then the material is shredded, screened, stockpiled, and blende d with other aggregate. Fi nally, it is moistened with water and added to the asphalt mixture. C oncerning the database, th e process description field is set to memo data type. This data type occupies more sp ace than text but is essential in this case. A more detailed disc ussion of processes can be found in Chapter 4. Performance Table This table provides the compendium of releva nt lab and field case studies. It is connected to the rest of the database through th e process table. The fields are: Authors, Reference, Year, State, and SummaryMemo. For example, a lab case study from the Geotechnical Testing Journal by Yang et al. ( 2002) analyzes the mechanical properties of scrap tires. Specifically, the unit weight, size, shape, cohesion, and friction angle of the material are documented. The reference information is inputted into the Performance table, and the engineering parameters are ad ded to the table that lists properties. Therefore, the database user may choose a process or a case st udy or an engineering property, and is immediately granted access to the other two pieces of information that correspond to that choice. Th e result is an interactive compendium of data that enables

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75 the users to start with one tabl e of data either because they choose to or because that is the only data to which they have access, and then move through the corresponding records in the other tables. Other Tables A linking table joins the Process table with the Performance table. It is necessary to model the many-to-many relationship that exists. The Case/Process table has the following fields: unit weight, spec ific gravity, shape, size, absorption, liquid limit, plastic limit, classification, hardness, CBR, cohesi on, maximum dry density, internal friction angle, optimum water content, compressive strength, othe r properties, and general environmental notes. Environmental tables in corporate the major constituents that may have a detrimental impact on the environment. Obviously, very few case studies depict all or even most of the above parameters. This fact does not detract from the usefulness of the database. Environmental parameters such as presence of trace metals, existence and composition of organics, leachate properties, and general environmental notes are also contained in tables that a ttach to the Case/Process tabl e. Again, each case study may provide very little information concerning en vironmental properties or it may be more comprehensive in nature. Using the Database The completed tables are the compendium of recycled materials data. However, it is the interaction and manipulati on of the data that gives the database its practicality. In the database management system, this is accomplished through the creation of forms, queries, and reports.

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76 Forms Forms serve as filters so users can see data in an easily accessible format (Whitehorn and Marklyn, 2003). Unless the user s are familiar with the database design and existing relationships between data sets, they cannot update it with new information. Typically, forms are the only method through whic h the user interacts with the data. For the recycled materials database, two sets of fo rms are created for each of the nine tables. As a result, the users can easily view existing information or they may add new recycled materials, new applications, new processes, new case studies, or new parameters to the database as the research is completed. The forms for viewing existing data are cr eated with functiona lity in mind. The user is not allowed to add to or edit informa tion to the database in any of the nine forms through the ‘view existing data’ form set. This is accomplished through locking the forms to which the data tables are connected. It is a safeguard against misuse and/or data contamination that may result from making the database available. The authors of this report and the database designer can only be held responsible for the design of the database. The ‘view existing data’ form set is formatted with a yellow and green background so that the users deve lop an awareness of where they are at in the database. An example form from the ‘view existing data’ form set is shown in Figure 5-2

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77 Figure 5-2: Case Process Form (‘View Existing Data’) The forms for adding new data are blank. Each form updates and is formatted to automatically increment primary key autonumbe rs each time a new record is added. One drawback is that as the users move from form to form entering data, they must click the “save” button to update the information they have already inputted into the corresponding data tables. Failure to do so negates any effo rts at data entry. Th e ‘add new data’ forms are equipped with a burgundy and gray bac kground so that the users are aware they should be adding new data. A form of this type is reproduced in Figure 5-3.

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78 Figure 5-3: Process Form (‘Add New Data’) Although not included in the database fr amework, forms may also be created from queries. A user can simply attach a form to a query. Each time the user types in a word, phrase, number, or other data in the ap propriate field, the query finds the relevant information and summarizes it for the user Connecting a form to a query merely improves the visual aspects of the user interacti on with queries. It is equally functional to allow the user to create a custom query with the help wizard or design his own. There are too many features provided by the database management system to design for each and every one. Queries One of the purposes of queries is to fi nd specific portions of data. They are questions that extract a subset of data di splayed in the form of a summary table.

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79 However, they also have the potential to pe rform mathematical mani pulation of existing data. General queries are created for some of the data subsets that attract interest. These include queries for each of the eight applic ations, queries for each of the twenty-four materials, queries for each of the over 50 pr ocesses, and queries for some of the more prolific authors of recycled ma terials case studies. In addition to the standard queries, the user has the option of creating custom queries. If for example, the user is only interested in a material or process that exhibits a cer tain compressive strengt h, a query may be used to display all the materials and processes that meet that criteria. The user may also create a custom query to avoid any process or cas e study that corresponds to a particularly troublesome chemical compound. Queries can be set up to search for incredibly detailed information or for more general lists. In additi on to queries that simply select data drawn from multiple tables, there are four more types. Table 5-1 lists all query types. Table 5-1: Types of Querie s (Whitehorn and Marklyn, 2003) Query Type Usage Select Select fields/records from table according to specified criteria Parameter Displays prompt boxes to supply query criteria Range Selects fields/records which contain a range of values Group By/Crosstab Displays summarized values (sums, averages) in a grid Action Performs actions to change records or create new tables In the given database, queries are created constantly to generate reports, view gaps in the data, and summarize information for presentations. An example query is created here for reference. The query assume s interest in all possible applications for coal fly ash. In addition, the assumption is ma de that the user wants to know the range of values for specific gravity as well as the hi gh end values for both internal friction angle and permeability. Figure 5-4 shows the desi gn view of the custom ‘select’ query.

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80 Figure 5-4: Fly Ash Query Design The output is generated in the form of a table, which combines the fields of interest from the Material, Application, and Ca se/Process tables. The output can be used to generate a report or form. Figure 5-5 shows the out put from the fly ash ‘select’ query. Figure 5-5: Fly As h Query Output

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81 Reports A report is simply a collection of summar ized information that is acceptable for printing. Unlike forms, their purpose is not user interaction. Instead, reports prepare data for printing and presentation. To function pr operly, the database does not require their creation. However, the user can easily cr eate custom forms from existing or custom queries to use in presentations or in hard c opies of documents. One such report is created below. Figure 5-6 shows a portion of the re port created from the ‘s elect’ custom query for fly ash. This time, the only information of interest is the material, fly ash, its applications, and range of specific gravity. Figure 5-6: Fly Ash Custom Report Interface The interface is setup to provide an aesthe tically pleasing ba ckdrop wherein the user can view existing data or add new data. The importance here is to provide an easily

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82 navigable interface so that the user does not get lost. This is accomplished by linking components of the interface to produce a seamless whole. Navigating Existing Data Forms When the user opens the database, a switc hboard opens that allows the user to choose between two options – ‘View Existing Data’ or ‘Add New Data.’ Choosing the first option takes the user directly to the fi rst form in the ‘view existing data’ set – the Material form. The Material form window actually opens on top of the switchboard, concealing it from view. The default view of the first record for the material, Paper, is showing. The user can scroll through all the record s in the Material ta ble, viewing each field in from the 24 records that correspond to the 24 materials. The user may then move to the next form in the sequence, the Appli cation form, by clicking on the next arrow and continue examining records or he may clos e the Material form by clicking on the back arrow. Each subsequent form window ope ns on top of the preceding form but may always be closed by clicking on the “Back” but ton. The final form in the sequence, the Leachate form, is equipped with an additional option of returning to the home or switchboard. The entire seque nce is as follows: Materi al, Application, Process, Performance, Case/Process, Chemical Co mposition, Metal Concentration, Organic Concentration, and Leachate. Navigating New Data Forms If the user instead chooses the s econd option, ‘Add New Data,’ a second switchboard opens revealing four additional ch oices. The user may ‘Add New Material,’ ‘Add New Application,’ ‘Add New Process,’ or ‘Add New Case Study.’ Each choice opens a different form that is separate from the ‘view existing data’ form set. These forms have burgundy and gray backgrounds, a nd their fields are initially blank. Choosing the first option will send the user to the Material (Add Entry) form into which the user can input a new material by typing it into the appropriate fi eld (MaterialName).

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83 Here the primary key, IDMaterial, automatically increments to the next number – in this case 25, and the rest of the fields within the form can be filled in by the user. A list box containing all existing materials is included for user reference. If for some reason the user enters a material that al ready exists, it will be possible to save the changes made to the form. This is because the property ‘index: Yes (no duplicates)’ in the field corresponding to material name has been sele cted. This is true for all fields where duplication would create confusion or otherwise slow the flow of data. After entering the information required, the entry is saved by clicking on the ‘save’ button and the user navi gates to the next form in th e series, the Application (Add Entry) form where a similar process is fo llowed. Upon continuing to the Process (Add Entry) form, a new process may be added. However, since a process is a unique material/application combina tion, a new process may be th e result of adding a new material, adding a new applica tion, adding both, or simply creating a new combination from an existing material and an existing pr ocess. To ensure consistency, the Process form is equipped with combo boxes, or pull-down boxes from which the user may select an existing IDMaterial and an existing IDApplication. The most recent of these values also shows up as the last entry in the c hoices within the combo box. When the user selects these values, a new IDProcess number automatically increments to create a new process. The second switchboard has four options to help the user control data input. For example, the user may need to add just a new material, or just a ne w application. Perhaps the user may choose instead to create a new process from an existi ng material and an existing application. In this case, choosing the option at the second switchboard to ‘Add New Process,’ allows skipping the first two form s. The same is true for the Performance (Add Entry) form, which permits a user to enter new reference information from a recent case study. In choosing any of the four options, the user w ill eventually work his way through the entire sequence of forms – savi ng each new record throughout. A partial flow diagram delineating user navigation between forms is shown in Figure 5-7.

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84 Figure 5-7: Interface Flow Diagram Modification It is impossible to design the database to cater to the needs of every engineering or research professional. The database is only a framework, albe it a robust one, which can be added to, improved, or even revampe d. A database profe ssional could certainly take advantage of features such as macros, sc ripts, or even create an improved interface through original code. On a more basic leve l, a designer might choose to add additional tables that organize pertinent recycled material data not included here In addition, fields can be added within existing tables or remove d at the discretion of the designer. It is envisioned that the relational database is the beginning – a fi rst step in bridging the gap between academic research and engineer ing practice in recycled materials. Switchboard View Existing Data Add New Data New Material New Case Stud y New Process New Application Materials I Materials II Application II Process II Performance II Type II For ms Type I Forms

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85 Chapter Six: Cost and Recommendations Cost Overview Quantifying the cost of recycled materials is a very difficult issue to address. This is the result of several factors. First, as a general observation, very little information is available regarding the cost of most recycled materials, which are cited in the literature. Researchers are much more concerned with evaluating engineering performance and even environmental impact of the materials rather than developing cost comparisons. Another problem with costs associated with waste mate rials is that they constantly fluctuate and change consistently over time. Over time, new taxes, environmental fines, restrictions, and inflation all have a progres sive effect on costs. In a ddition, costs change as a result of improvements in recycling processes a nd variations in market conditions. For example, twenty years ago, very few tire-re cycling firms even existed. As of the beginning of 2004 however, some 41 tire recycl ing facilities are located in Florida alone (DEP, 2003). The increase in firm competitiveness and productivity has driven down both direct and indirect costs. Another pr oblem with quantifying costs stems from the large discrepancies in waste material cost and availability on both a national and a local level. Transport costs and premium costs a ssociated with limited material availability can be greatly affected. Finally, cost an alysis sometimes takes into account more subjective criterion such as cost to landfill and cost to the environment if the materials are not reused. In short, cost is difficult to quantify for researchers, engineering professionals, and database designers.

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86 Considerations Comparison is a key issue in recycled mate rial research. Waste materials must be compared to the traditional materials that they are replacing, and waste materials must be compared to each other. Perhaps the first c onsideration for the use of any material is adequate engineering performance. If the waste material functions adequately in the specified application, it can at least be consid ered for potential use. However, once this criterion has been met, the cost of the recycl ed material must be compared to established materials such as select fill, aggregate, etc. It is difficult to make the case for using a particular recycled material if the costs a ssociated with it are higher than those of accepted materials. One possible exception oc curs when materials are mandated for use through government legislation or bureaucratic regulation. In th is case, cost is barely a consideration. However, this case will not be addressed here. Instead, recycled materials will be examined theoretically from a co mprehensive consideration of all cost components. Cost Breakdown Although very few researchers have addres sed cost in inves tigating the use of recycled materials, Chesner et al. (2002) deve lops cost considerati ons by borrowing from the economics of manufacturing. Specifically, three components are examined: cost of the material, cost of installation, and life-cycle cost. It is the opinion of the author that a fourth cost, environmental cost, should also be considered in the analysis. Material Cost The material cost is associated with wh at the buyer – in this case the engineering firm, contractor, or agency woul d pay to have the material on site and available for use. The seller would be the material supplier, recy cling firm, or material handler. Equation 1 is proposed by Chesner et al. ( 2002) to express material cost:

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87 ) 1 ( Eq P C C C C P CTR LD ST PR RM DP where, CDP = Delivered price PRM = Raw material price CPR = Processing cost CST = Stockpiling cost CLD = Loading cost CTR = Transporting cost P = Profit It must be emphasized that the compone nts of the equation are necessary only when there exists a significant difference in the cost in comparison to similar costs associated with traditional materials. Fo r example, transporting may be necessary for select fill as well as for scrap tires. However, due to the large void ratio of scrap tires in relation to select fill, more truckloads may be required thereby increasing the cost. Transporting, loading, and stockpiling cost s are all self-explanatory. However, it must be mentioned that the raw material price can essentially have a positive or negative value. In general, if a recycler or processing firm sells the material, the raw material price will be positive, wher eas if a manufacturing plant or production facility must otherwise dispose of the waste material for a fee, the raw material price will be negative (Chesner et al., 2002). Processing costs ar e those associated w ith refining a waste material so that it can be used. This involves shredding, crushi ng, screening, presorting etc. Processing costs are extremely variable depending on the material that is processed, processing requirements, and establishment of the recycling market. For example, economies of scale allow shredded tires to be produced at a lower per unit cost than several other materials that require markedly less processi ng. Profit is also highly variable.

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88 Installation Cost The engineering firm or contractor may pl an to subcontract th e installation out or they may be interested in potential incurred co sts as a result of installation. In addition, some materials require mon itoring of both engineering systems and environmental impact. Some pre-testing of the material mi ght also be necessary. Chesner et al. (2002) proposes Equation 2 to address such costs. Again, these co mponent costs are only taken into account when there is a significant difference between th e recycled material and the material for which it is substituting: ) 2 ( Eq T C C CRP C DR I where, CI = Installation cost CDR = Design cost CC = Construction cost TRP = Testing/inspection cost Life-Cycle Cost To further the comparison, it is important to consider the effect that the use of a recycled material in lieu of an establishe d material has on maintenance or upkeep. This borrows from the economics of manufacturing in which the cost of a new machine must be compared to an older machine requiring yearly maintenance. Equation 3 proposed by Chesner et al. (2002) is basica lly an equivalent annuity calc ulated from a combination of maintenance costs, interest rates, and product life:

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89 ) 3 ( ) ( Eq C n i CRF C AAM I EC where, AEC = Annual effective cost CI = Installation cost (Eq. 2) CRF(i,n) = Capital recovery factor (per cent interest, i, and product life, n) CAM = Annual maintenance cost Life-cycle cost is only an issue when recycled material use results in additional requirements in terms of maintenance and repair For example, an asphalt pavement road may require supplementary maintenance techniques in addition to more regular servicing. Environmental Cost Although not included in the preceding cost analysis, environmental cost is very real and must be included for the sake of completeness. Unfortunately, environmental cost is much more esoteric – requiring subj ective evaluation. It includes the potential environmental costs associated with not using a particular material. It might also include costs associated with mandated environmental cleanup as well as costs required to deal with problems of rapidly-filling landfills. No equation is proposed here to deal with this cost. Database and Cost From the database standpoint, it is not advisable to include cost in its current format. Currently, cost per ton is a field in the Process table. In other words, for each material/application combination, there is a total cost associat ed with it. However, this oversimplifies the cost issue as evidenced by the previous discussion. It has been proposed to include the cost in addition to the year in whic h the cost data or quote was obtained. Other suggestions include providing a local or source-specific framework in

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90 which to view the evolution of cost over tim e and by region. These topics are ambitious and might be better suited for a separate database. However, they represent some interesting directions for the research. Recommendations This section is meant not to present conc lusions on the use of precise materials in specified applications. Rather this information should be drawn by the read er of this paper and the user of the database. The focus is placed on more qualitative recommendations, suggestions for further re cycled material research, and additional database feature propositions. In addition, a fundamental question from the research must be asked. Does the recycled material relational database adequately address the redefined problem presented in Chapter 1? General Recommendations From reading the literature and speaki ng with engineering professionals, it is apparent that a quality control mechanism mu st be in place if th e goal of recycled materials implementation is to be achieved. Perhaps the most expeditious method to achieve it is through source cont rol. By ensuring that a material comes from the same source and is processed in a consistent wa y, many of the variable s associated with engineering performance and environmental imp act can be at least partially controlled. The wide range of engineering parameters especially for unit weight, CBR, internal friction angle, permeability, and compressi ve strength emphasize the need to test materials at the local level from a controlled source using specified sampling procedures Once consistency can be established, and more importantly assured at the local level, the use of recycled materials will be greatly faci litated. High up-front costs associated with quality control through testing s hould lead to lower costs in th e future. In addition, it is advisable to involve national and state envi ronmental organizations such as EPA and DEP at every stage. Besides agency control of recycled materials, another option is to

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91 place the burden of quality control squarely on the sellers – recycli ng firms and materials generators. The responsibility of presorting, processing, test ing, and possibility transport – all to achieve a quality product, will be ha ndled by those profiting from the sale of the material. Additional Research As a result of this study and the databa se, certain gaps in recycled material research have surfaced. These gaps can be f illed with appropriate laboratory and field testing to completely characterize the mate rial properties and potential uses. It is suggested that three materials be investigated further: roof shingles (prompt and tear-off), paper mill sludge, and plastic. Little research has been done on both roof shingles and paper mill sludge, and plastic use thus far has been promising. Plastic should be investigated further in soil stabilization, and potential suppl ementary applications should be explored. Another avenue of research involves the development of construction guidelines and required field equi pment so as to be able to actually build with recycled materials. Examples include guidelines a nd equipment to install discrete recycled material stabilizers such as plastic piles or to homogenously mix marginal soils onsite with property-enhancing waste material component s or fibers. It may also be beneficial to develop candidate applications for the use of different recycled materials depending on site conditions, soil t ype, and other factors. Database Recommendations The addition of several components has been suggested and their incorporation into the database may be beneficial to both acad emics and engineers. The first is to bring some element of local availability and cost into the database. This would require investigating local market sour ces of each recycled material. In this way, a user would have access to a variety of pertinent information. For example, three different plants might sell a particular recycled material fo r a specified price with a given list of

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92 engineering properties and longterm environmental impact data. Access to this kind of information would be invaluable not only to de sign engineers and contractors, but also to state agencies and environmental organizati ons. A general database recommendation is to develop parameter or select queries to be connected to the inte rface through their own form set. Finally, the debugging process must continue, the interface can be improved, and wider access to the database can be achieved by making the database available online. Conclusion This study addresses the challenges of impl ementing a recycled material program. Its purpose is to bridge the gap between qua lity academic research on recycled materials and implementation of this research in engin eering practice. The creation of a recycled material relational database resolves several issues. First, it provides a single resource that contains relevant data and case studies on the materi als, their applications and processes, and the numerous environmental an d engineering propertie s that characterize them. Information is organized through a seamless interface that consists of forms connected to the rest of the database with tables. Second, the relational model allows rapid sorting of data. Existi ng and customizable queries can be used to find subsets of data that are tailored to the user’s interests. The information can in turn be used to implement a recycled material program. Finally, the user can amend existing data, update the database to keep pace with curr ent research, or modify the design of the original database. In short, it is envisioned that the re cycled material relational database will serve as a flexible, usable tool for professionals seeking to implement recycled material programs.

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93 References Abichou, T., Benson, C.H., Edil, T.B., Freber, B.W. (1998), Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 86-99. Aerotech Environmental Laboratories, (2004), Leaching Procedures Accessed on June 15, 2004. http://www.palabs.com/Resources/splp_limits.asp. Bosscher, P.J., Edil, T.B., and Kurako, S. (1997). “Design of highway embankments using tire chips.” J. of Geotech. and Geoenviron. Eng ., Vol. 123, No. 4, pp. 295-304. Chesner, W. H., Simon, M.J., Eighmy, T.T. (2003). “Recent federal initiatives for recycled material use in highway construction in the United States.” Beneficial Use of Recycled Materials in Transportation Applications, The Recycled Material Resource Center, T.T. Eighmy, Eds., pp. 3-10. Chesner, W., Stein, C., Collins, R., and MacKay, M. (1998), National Cooperative Highway Research Program Waste and R ecycled Materials Information Database Accessed on January 7, 2004. http://w ww.rmrc.unh.edu/Resources/PandD/NCHRP. Chesner, W., Collins, R.J., MacKay, M., and Emery, J. (2002), User Guidelines for Waste and Byproduct Materials in Pavement Construction Accessed on January 15, 2004. Collins, R.J., and Ciesielski, S.K. (1994), “R ecycling and use of waste materials and byproducts in highway construction.” National Cooperative Highway Research Program Synthesis of Highway Practice 199 National Academy Press. Consoli, N.C., Montardo, J.P., Prietto, P. D.M., and Pasa, G.S. (2002). “Engineering behavior of a sand reinfor ced with plastic waste.” J. of Geotech. and Geoenviron. Eng., Vol. 128, No. 6, pp. 462-472. Department of Environmental Protection (2003) “Waste tires in Florida, state of the state.” Accessed on January 17, 2004. http://www.dep.state.fl.us/waste. Edil, T.B, and Benson, C.H. (1998), “Geo technics of industr ial by-products.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 1-18.

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94 Fahoum, K. (1998), “Utilizati on of lagoon-stored lime in embankment construction.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 115-121. Humphrey, D.N., Whetten, N., Weaver, J., Recker, K., Cosgrove, T.A. (1998), “Tire shreds as lightweight fill for em bankments and retaining walls.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 51-65. Kim, A.G. (2003), CCB Leaching Summary: Survey of Methods and Results Accessed on June 15, 2004. http://www.mcrcc.osmre.gov/PDF/Forums/CCB3/4-2.pdf. Liu, H.S., Mead, J.L., and Stacer, R.G. (2000). “Environmental effects of recycled rubber in light-fill applications.” Rubber Chem. Technol., Vol. 73, pp. 551-564. Loehr, J.E., and Bowders, J.J. (2000). “Slope stabilization with recycled plastic pins.” Geotechnical News Vol. 18, No. 1, pp. 41-44. Mast, D.G., and Fox, P.J. (1998). “Geotechni cal performance of a highway embankment constructed using waste foundry sand.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 66-85. O’Shaughnessy, V., and Garga, V.K. (1999). “Tire-reinforced earthfill. Part 3: environmental assessment.” Can. Geotech. J. Vol. 37, pp. 117-131. Papp, W.J., Maher, M.H., Bennert, T.A., and Gucunski, N. (1998), “Behavior of construction and demolition debris in base and subbase applications.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 122-136. Quiroz, J.D., and Zimmie, T.F. (1998), “Pap er Mill Sludge Landfill Cover Construction.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 19-36. Reid, R.A., Soupir, S.P., Schaefer, V.R. (1998), “Mitigation of void development under bridge approach slabs using rubber tire chips.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 37-50. Senadheera, S.P., Jayawickrama, P.W., and Rana, A.S.M. (1998), “Crushed hydrated fly ash as a construction aggregate.” Recycled Materials in Ge otechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds, pp. 167-179. Tandon, V., Picornell, M. (1998), “The safe di sposal of fly ash in pavement or earth structures not requiring high strength materials.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 153-166.

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95 Vipulanandan, C., and Bashaeer, M. (1998) “Recycled materials for embankment construction.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 100-114. Vipulanandan, C., Weng, Y., and Zhang, C. (1998) “Role of constituents on the behavior of flowable fly ash fill.” Recycled Materials in Geotechnical Applications, ASCE GSP 79, C. Vipulanandan, and D.J. Elton, Eds., pp. 137-152. Wang, Y. (1999). “Utilization of recycled ca rpet waste fibers for reinforcement of concrete and soil.” J. of Polym.-Plast. Technol. Eng ., 38(3), 533-546. Whitehorn, M., and Marklyn, B. (2001). “Ins ide Relational Databases.” A book published by Springer. London. Whitehorn, M., and Marklyn, B. (2003). “Accessible Access 2000.” A book published by Springer. London. Yang, S., Lohnes, R.A., and Kjartanson, B.H. (2002). "Mechanical properties of shredded tires.” Geotechnical Testing J., Vol. 25, No. 1, pp. 44-52.