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User Guidelines for Waste and Byproduct Materials in Pavement Construction

PURPOSE

As the volume of waste and by-product materials generated in our society and the cost of disposal continue to increase, there is increased pressure and incentive to recover and recycle these materials for use in secondary applications. Because the construction of pavements requires large volumes of materials, highway agencies have become participants in these recycling efforts.

From a pavement engineering perspective, recovered materials should be used in such a manner that the expected performance of the pavement will not be compromised. Waste and by-product materials, however, differ vastly in their types and properties and, as a result, in the pavement applications for which they may be suited. Experience and knowledge regarding the use of these materials vary from material to material as well as from state to state. To recover these materials for potential use, engineers, researchers, generators, and regulators need to be aware of the properties of the materials, how they can be used, and what limitations may be associated with their use.

The primary purpose of this guideline document is to assist those who have an interest in using or increasing their understanding of the types of waste and by-product materials that may be recovered and used in pavement construction applications. It is intended to provide the potential user or reviewer with sufficient information on each material included in this document so that he or she will have an understanding of the nature of the material, where other information may be obtained, and what issues need to be evaluated when considering its use. It is also intended to provide the reader with general guidance on engineering evaluation requirements, environmental issues, and economic considerations for determining the suitability of using recovered materials in pavement applications.

Because of the ongoing development and publication of new information regarding the use of recovered materials in highway applications, this document has been designed in a looseleaf format to permit periodic revisions and updates.

SCOPE

These guidelines cover the use of waste and byproduct materials in six major highway construction applications: (1) Asphalt Concrete; (2) Portland Cement Concrete; (3) Granular Base; (4) Embankment or Fill; (5) Stabilized Base; and (6) Flowable Fill. In each of these primary application categories, there is at least one possible material use, and in some cases there are several potential uses. For example, in Portland Cement Concrete, a material may be used as aggregate or as a supplementary cementitious material. Table 1-1 lists the primary applications and the types of material uses in each respective application.

Table 1-1. Highway and pavement applications and material uses.

This document includes guidelines for 19 waste and by-product materials. Listed in alphabetical order, they include: (1) Baghouse Fines; (2) Blast Furnace Slag; (3) Coal Bottom Ash/Boiler Slag; (4) Coal Fly Ash; (5) Flue Gas Desulfurization (FGD) Scrubber Material; (6) Foundry Sand; (7) Kiln Dusts; (8) Mineral Processing Wastes; (9) Municipal Solid Waste (MSW) Incinerator Ash; (10) Nonferrous Slags; (11) Quarry By-Products; (12) Reclaimed Asphalt Pavement; (13) Reclaimed Concrete Material; (14) Roofing Shingle Scrap; (15) Scrap Tires; (16) Sewage Sludge Ash; (17) Steel Slag; (18) Sulfate Wastes; and (19) Waste Glass.

The materials listed above do not represent the entire population of materials that have potential use in pavement construction applications. These 19 materials were selected based on the amount of the material generated as well as whether adequate data were available to prepare a description of the physical and chemical properties of the material and to describe the design requirements and performance records for one or more specific applications.

For the 19 materials and 6 major application categories, a total of 55 material-application combinations were selected and are included in these guidelines. Table 1-2 provides a listing of these 55 combinations. The omission of a particular material-application match in these guidelines is not to be construed as a prohibition against its use; rather, omission merely indicates that the authors felt that either the material-application combination was inappropriate or that insufficient information was available to provide a useful guideline.

The major portion of this document presents, for each of the 19 materials, a description of the material and user guidelines that includes the applications listed in Table 1-2. In addition to material-specific guidelines, several chapters of the report are devoted to recommended evaluation procedures for assessing whether a material is suitable for use in a designated application and to the environmental and cost issues that need to be considered when evaluating the use of waste and by-product materials in pavement construction. Finally, summary descriptions of the six pavement construction applications are presented to assist those readers who are interested in additional information relative to their design objectives and material uses.

Table 1-2. Application—material matrix.

ORGANIZATION AND CONTENT

This document is divided into 24 chapters. The contents of the chapters are described below.

Introduction

Chapter 1, the Introduction, provides an overview of the purpose, scope, and organization of this document.

Material-Specific Guidelines

Chapters 2 through 20 present the material-specific guidelines, one for each of the 19 materials included in the document. Each of these chapters contains a Material Description section and one or more User Guideline section(s).

The Material Description sections are divided into five subsections: (1) Origin; (2) Current Management Options; (3) Market Sources; (4) Highway Uses and Processing Requirements; and (5) Material Properties.

Origin: The Origin subsection presents a general description of the material, its industrial origin, the quantity of material generated annually in the United States, and other sources of information (e.g., trade associations) on the subject material.

Current Management Options: The Current Management Options subsection provides a description of present recycling and disposal practices.

Market Sources: The Market Sources subsection identifies locations or suppliers from whom the material can be obtained and special characteristics of the material that should be of interest to a prospective recycler.

Highway Uses and Processing Requirements: The Highway Uses and Processing Requirements subsection describes highway uses for which the material may have some proven or potential application as well as processing requirements that will be needed prior to use.

Material Properties: The Material Properties subsection provides a description of the physical, chemical, mechanical, and other properties that should be of interest to a prospective recycler.

Each User Guideline section is divided into seven subsections: (1) Introduction; (2) Performance Record; (3) Material Processing Requirements; (4) Engineering Properties; (5) Design Considerations; (6) Construction Procedures; and (7) Unresolved Issues.

Introduction: the Introduction subsection of each User Guideline presents a description of the role of the material in the designated application.

Performance Record: The Performance Record subsection describes the extent of prior experience and the advantages and disadvantages of using the material in the designated application.

Material Processing Requirements: The Material Processing Requirements subsection outlines the processing needs (e.g., cleaning, crushing, screening, etc.) that are required prior to use of the material in the designated application.

Engineering Properties: The Engineering Properties subsection presents a description of the properties that will be of particular interest to a prospective recycler who is considering the use of the material in the designated application.

Design Considerations: The Design Considerations subsection outlines the relevant mix design and structural design issues that are of interest when using the material in the designated application.

Construction Procedures: The Construction Procedures subsection describes special material handling, storage, mixing, curing, and placement issues that can arise when using the material in the designated application.

Unresolved Issues: The Unresolved Issues subsection summarizes important issues that are either unknown or need to be studied further to assist in making more widespread use of the material possible in the designated application.

Evaluation Guidance

Chapters 21, 22, and 23 are Evaluation Guidance chapters. Chapter 21 outlines a recommended framework for evaluating waste and by-product materials for use in pavement construction applications. It includes a description of the major steps that should be included in any evaluation process. The chapter is organized to address the requirements of each of the steps in this process.

Chapter 22 provides guidance relative to the environmental issues that a prospective recycler should be cognizant of when considering the use of waste and by-product materials in pavement construction applications. It includes a description of legislation and regulations that could have an impact on waste and by-product material use and outlines procedures that are available to assess potential health, environmental, and ecological impacts associated with the use of waste and by-product materials in pavement construction applications.

Chapter 23 provides guidance relative to economic issues that a prospective recycler or evaluator should consider when considering the use of waste and by-product materials in construction applications. It includes a description of recommended methods for calculating the cost of a recovered material, the cost of installation when incorporating a recovered material into a pavement, and the life cycle cost of the product when using a recovered material in pavement construction applications.

Application Descriptions

Chapter 24 contains descriptions of the six applications listed in Table 1-1, and is intended for the reader who is interested in more detailed information about these applications. Each section of this chapter includes a general description of the application, a description of conventional materials typically used in the application and the desirable properties of those materials, and a description of the testing methods that are commonly used to evaluate the properties of these materials as they pertain to the designated application.

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