• Introduction
• Matrix New!
• Glossary New!
• Notice

• Environmental and Engineering Evaluation New!
• State Contacts New!
• Cost Issues
• Standards/Specifications New!

• Baghouse Fines
• Blast Furnace Slag
• Coal Bottom Ash/Boiler Slag Updated!
• Coal Fly Ash Updated!
• FGD Scrubber Material Updated!
• Foundry Sand Updated!
• Kiln Dusts
• Mineral Processing Wastes
• MSW Combustor Ash
• Nonferrous Slags
• Quarry Byproducts
• Reclaimed Asphalt Pavement Updated!
• Reclaimed Concrete Material Updated!
• Roofing Shingle Scrap Updated!
• Scrap Tires
• Sewage Sludge Ash
• Steel Slag
• Sulfate Wastes
• Waste Glass

• General Descriptions
• Asphalt Concrete Pavement
• Portland Cement Concrete Pavement
• Granular Base
• Embankment or Fill
• Stabilized Base
• Flowable Fill

INTRODUCTION

PURPOSE

As virgin materials become scare and the volume of 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 highways requires large volumes of materials, transportation agencies have become participants in these recycling efforts. From a highway engineering perspective, recovered materials should be used in such a manner that the expected performance of the highway will not be compromised. By-product materials, however, differ vastly in their types and properties and, as a result, in the highway 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 guidance document is to assist those who have an interest in using or increasing their understanding of the types of by-product materials that may be recovered and used in highway 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 highway applications.

Because of the ongoing development and publication of new information regarding the use of recovered materials in highway applications, this site may be updated periodically. A 2007 update includes new information for the following materials and their applications: coal bottom ash/boiler slag, coal fly ash, FGD scrubber material, foundry sand, reclaimed asphalt pavement, recovered concrete material, and roofing shingle scrap. The rest of the information on materials is current as of 1995.

MATRIX

These guidelines cover the use of 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. This document includes guidelines for 19 by-product materials. The matrix below provides an easy method of navigating the material-application combinations. The materials do not represent the entire population of materials that have potential use in highway construction applications. These 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. 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 the matrix. 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 by-product materials in highway construction. Finally, summary descriptions of the six highway construction applications are presented to assist those readers who are interested in additional information relative to their design objectives and material uses.

ORGANIZATION AND CONTENT

Material and Application-Specific Guidelines

The Material Description sections are divided into the following six subsections.

1. Origin: 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
2. Current Management Options: provides a description of present recycling and disposal practices.
3. Market Sources: 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.
4. Highway Uses and Processing Requirements: 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.
5. Material Properties: provides a description of the physical, chemical, mechanical, and other properties that should be of interest to a prospective recycler.
6. Environmental Considerations: provides a description of the potential environmental issues related to the use of the specific material for all applications.

Each User Guideline section is divided into the following eight subsections:

1. Introduction: presents a description of the role of the material in the designated application.
2. Performance Record: describes the extent of prior experience and the advantages and disadvantages of using the material in the designated application.
3. Material Processing Requirements: outlines the processing needs (e.g., cleaning, crushing, screening, etc.) that are required prior to use of the material in the designated application.
4. Engineering Properties: 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.
5. Design Considerations: outlines the relevant mix design and structural design issues that are of interest when using the material in the designated application.
6. Construction Procedures: describes special material handling, storage, mixing, curing, and placement issues that can arise when using the material in the designated application.
7. Environmental Considerations: provides a description of the potential environmental issues related to the use of the material for the specific application.
8. Unresolved Issues (if applicable): 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

The Evaluation Guidance outlines a recommended framework for evaluating by-product materials for use in highway construction applications. It includes a description of the major steps that should be included in any evaluation process and is organized to address the requirements of each of the steps in this process.

There is also guidance relative to the environmental issues that a prospective recycler should be cognizant of when considering the use of by-product materials in highway construction applications including a description of legislation and regulations that could have an impact on by-product material use and outlines procedures that are available to assess potential health, environmental, and ecological impacts associated with the use of by-product materials in highway construction applications.

There is also guidance relative to economic issues that a prospective recycler or evaluator should consider when considering the use of by-product materials in construction applications including a description of recommended methods for calculating the cost of a recovered material, the cost of installation when incorporating a recovered material into a highway, and the life cycle cost of the product when using a recovered material in highway construction applications.

Application Descriptions

This section contains descriptions of the six applications, 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.