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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Public Roads - July/August 2000

The Recycled Materials Resource Center

by Bryan J. Magee

The Recycled Materials Resource Center (RMRC) is a national center created to promote the appropriate use of recycled materials in the highway environment. Recycled materials are generally defined as recycled bituminous and concrete pavement materials and as secondary, byproduct, and waste materials.

The center was formally established on Sept. 4, 1998, as a partnership between the University of New Hampshire (UNH) and the Federal Highway Administration (FHWA). It was authorized by Section 5117(b)(8) of the Transportation Equity Act for the 2lst Century (TEA-21) in 1998 and was initially funded for six years.

RMRC has a unique role in the growing field of recycled materials use in highway construction — that is, to serve as a catalyst to reduce barriers to the appropriate use of recycled materials in the highway environment. The center is a culmination of a number of diverse, but integrated, efforts by FHWA, other federal and state agencies, and academia to provide a cohesive approach to the complex engineering and environmental issues surrounding the use of recycled materials. RMRC will not only serve as a principal evaluator of information in this area for FHWA, but it will also focus on outreach activities and provide a main point of contact for information.

The center is staffed with a director, associate director, Outreach Program project director, information technologist, program assistant, research faculty, and graduate and undergraduate students. An advisory board of experts from state and federal agencies, trade associations, and the private sector has been established to provide guidance and connections to many highway constituencies.

The RMRC staff: (left to right) Dr. Byran Magee, Tom Kurshinsky, Colleen Mitchell, Dr. Kevin Gardner, Dr. Taylor Eighmy. (Photo by RMRC)

The center staff has prepared a strategic plan, annual work plans, a practices and procedures manual, self-evaluation plans, performance measure plans, and cost-sharing and financial plans to assist in operations.

Mission and Focus

As stipulated in TEA-21 and in the cooperative agreement between FHWA and UNH, the mission and functions of RMRC include:

  • Systematically testing, evaluating, and developing appropriate guidelines.
  • Making information available to its clients.
  • Encouraging the increased use of recycled materials by analyzing potential long-term considerations that affect performance.
  • Working cooperatively with federal and state officials to reduce the institutional barriers and ensure sustained environmental and physical integrity.

To fulfill this mission, the center has identified seven principal areas of focus:

  • Testing and evaluation guidelines and specifications.
  • Material-specific research and development.
  • Economics and institutional issues of secondary materials.
  • New materials and innovative technologies.
  • Field trials of secondary materials.
  • Technical services.
  • Technology transfer and training.

RMRC is concentrating on both research and outreach activities to help accomplish its mission. The principal clients are state departments of transportation and state environmental regulatory agencies.


Approximately 30 research projects will be funded and conducted by RMRC over the first six years of operation. Awarded through a national request for proposal and peer review process, 10 research projects are already underway. Four projects are being conducted internally by RMRC personnel. It should be noted that further research funding will be made available in early 2001 when a second request for proposals will be issued by the center.

While a summary of these ongoing research projects follows, up-to-date information about their progress may be obtained from the center’s Web site (

Project 1 — Mitigating Alkali-Silica Reaction in Recycled Concrete

This project, conducted by Dr. David Gress of UNH, is taking place during years 1 through 3. Its focus is on the production of concrete containing recycled concrete aggregate (RCA), where the recycled concrete is suffering from alkali-silica reaction (ASR).

ASR is a deleterious reaction between reactive silica in some aggregates and alkali present in the concrete pore water. The alkali causes the reactive silica to go into solution, and it is deposited as a gel, which expands when external water enters the concrete. This expansion leads to cracking and deterioration of structures and pavements over a period of years. A significant portion of the country’s infrastructure is suffering from this dilemma. This makes it difficult to recycled concrete with ASR present as the reaction can continue within the new concrete matrix. It would be invaluable to have a better knowledge of how to mitigate ASR. In addition, to be able to successfully recycle ASR-affected structures as an aggregate source in new concrete would save our quickly declining supply of mineral aggregates.

Methods are being investigated to more quickly evaluate a given concrete for its ASR potential. Traditional methods such as ASTM 1260 and ASTM 1293 are being modified by using different sample geometries, electric fields, and microwaves to more quickly detect ASR in concrete made with recycled concrete aggregate (RCA). Electric fields and microwaves are also being used to accelerate the reaction in field cores obtained from pavements known to have ASR to determine their remaining ASR potential.

A new test procedure for evaluating the use of RCA in concrete with and without mitigation will be proposed to the American Association of State Highway and Transportation Officials (AASHTO) for their consideration as a recognized test method. Guidelines will also be developed to allow state departments of transportation (DOTs) to evaluate a given RCA for recycling in concrete. Numerous state DOTs and industrial partners are involved in this project.

Project 3 — Environmental Weathering of Granular Waste Materials Impact on Environmental Performance

Dr. Kevin Gardner of UNH will conduct this project during years 1 through 3. Work involves the environmental evaluation of a variety of granular wastes from high-temperature industrial processes, and it allows an understanding of the geochemical aging and weathering characteristics of these materials. Chemical and physical changes are being assessed using a variety of techniques to enable the prediction of the long-term environmental performance of these materials when used in the highway environment. Techniques are being developed to accelerate the weathering of the material to produce a more physically and chemically stable product. State environmental protection agencies (EPAs) and industrial partners are involved in this project.

Project 5 — Concrete Mixtures With Inclusions to Improve the Sound-Absorbing Capacity of PCC Pavements

Dr. Bryan Magee of UNH and Dr. Jan Olek of Purdue University are undertaking this project during years 2 through 4. The goal of this project is to develop portland cement concrete (PCC) pavements with high surface friction and reduced tire/pavement noise-generating characteristics. In this way, the work is intended to address the rising number of complaints about tire/pavement noise from residents living in areas adjacent to highways; many states are now mandating corrective actions to reduce noise, especially on urban stretches of highway. The study is based on the premise that pavements containing a reasonable volume of flexible and/or porous inclusions will reduce the resonance and/or reflection of the sound waves while also absorbing a portion of the air volume change generated by the tire interacting with the pavement. This study will develop an alternative and novel system for effective control of pavement noise generation. In addition to solving this important environmental concern, this study will also promote increased use of recycled materials in the highway environment.

Project 7 — Development of Application-Specific Source Term/Fate/Transport Models and Approaches for Recycled Materials Use in the Highway Environment

Dr. Taylor Eighmy and Dr. Kevin Gardner of UNH will conduct this project during years 2 through 5. There is a need for state environmental regulatory agencies to have a more realistic and mechanistic way of assessing the risk, if any, of uses of certain recycled materials in unbound and bound applications, such as concrete and asphalt pavements, base course, sub-base, embankments, and flowable fills. Presently, states use a variety of means to assess impact — for example, batch leaching tests, composition comparison, clean soil standards, and the use of risk analysis. Methods are needed that take into consideration the hydraulic regime of the application (saturated, unsaturated, intermittent wetting, drying, aging), the nature of contaminant release (diffusion, advection), the role of the application/soil interface and the unsaturated zone above the water table, and subsequent transport. The principal objectives are to: (1) identify state-of-the-art practices in Europe, the state agencies, and the U.S. Environment Protection Agency for beneficial use determinations or related scenarios; (2) identify needs and use of applicable approaches; (3) synthesize and develop an appropriate, verifiable mechanistic source term/fate/transport model that addresses contaminant release from various application scenarios (pavements, embankments, etc.) and its subsequent transport in ground water; (4) provide for state agencies a simplified model or approach that embodies the principles of the source contaminant release and transport. This model would first be used for looking at inorganic contaminants. It may be modified later for organic contaminants. The proposed end products are a mechanistic contaminant release and transport model for inorganic contaminants that will be field-verified and a simplified model or approach that embodies the principles of the contaminant release and transport model for use by regulators.

Project 11 — Leaching From Granular Materials Used in Highway Construction During Intermittent Wetting

Dr. David Kosson of Vanderbilt University will conduct this research during years 1 through 3. The goal of this project is to develop testing and interpretation protocols to estimate constituent leaching from granular waste materials that are used as aggregate in unbound highway construction applications (embankments, sound barriers, fill, base course). The resulting test methods and interpretation protocols developed, including appropriate mathematical models, will then be used to evaluate the environmental impact of specific proposed secondary material applications. The primary focus of this work is on leaching conditions that occur as a consequence of intermittent infiltration (wetting and drying, carbon dioxide uptake, oxygen uptake) into the granular material. End-users can adopt the protocols based on the need to evaluate the potential environmental impact for both liability and regulatory assessment. State DOTs, state EPAs, and industrial partners are involved in this project.

Project 13 — Development and Preparation of Specifications for Recycled Materials in Transportation Applications

Dr. Warren Chesner of Chesner Engineering Inc. conducted this project during year 1. It addressed the need for appropriate specifications for using recycled materials in the highway construction environment. Fourteen state DOTs from around the nation participated in the development of common specifications for a number of types of secondary materials within these states. Draft specifications have been submitted to AASHTO for consideration as formal specifications.

Project 15 — Determination of Ndesign for CIR Mixture Design Using the SGC

Dr. Stephen Cross of the University of Kansas conducted this research project during year 1. Work focused on determining the number of compaction revolutions (Ndesign) required in the SHRP gyratory compactor (SGC) in order to duplicate field unit weights of cold-in-place recycled (CIR) asphalt mixtures. This work resulted in the development of compaction protocol for CIR materials, and it should remove the final barrier to the further adaptation of CIR technology. State DOTs and industrial partners were involved.

Project 17 — Development of a Rational and Practical Mix Design System for Full-Depth Reclamation

Dr. Rajib Mallick of Worcester Polytechnic Institute, in collaboration with members of the National Center for Asphalt Technology (NCAT) at Auburn University, conducted this project during years 1 and 2. The aim was to develop a rational and practical mix design system for full-depth reclamation (FDR). Specifically, the objectives were to develop methods for determining curing periods and the number of gyrations required in the SGC to produce in-place densities and to compare the effectiveness of four different types of additives used for FDR at a specific location in Maine. The resulting mix design system produces mixes with consistently good performance, thereby enhancing confidence in the use of FDR and encouraging the increased use of recycled materials. Maine DOT was also a principal investigator with the project.

Project 18 — Fatigue Durability of Stabilized Recycled Aggregate Base Course Containing Fly Ash and Waste-Plastic Strip Reinforcement

Dr. Khaled Sobhan of New Mexico State University conducted this research project during year 1. The project evaluated the technical performance of a new composite base course made from crushed RCA, portland cement, high volumes of coal fly ash, and strips of shredded reclaimed plastics. The primary purpose of this project was to identify an innovative use for recyclable materials in highway pavements by conducting systematic characterization studies aimed at providing valuable insights into the long-term performance and durability issues of such composites. State DOTs and industrial partners were involved in this project.

Project 19 — Lightweight Synthetic Aggregate From Fly Ash and Waste Plastics

Dr. Mohsen Kashi of GEI Consultants in Winchester, Mass., conducted this project in collaboration with colleagues from the University of Massachusetts at Lowell and fromTufts University during year one. In this project, a new product was developed from fly ash and waste plastic — two materials currently sent to the disposal facilities. The final product, a lightweight synthetic aggregate, is a granular material that can be used in such applications as lightweight fill, pre-cast concrete elements, concrete structures, and insulation for utility pipelines. This project considered the use of various fly ash-to-plastic ratios, plastics of different thermal properties, and various production methods. The project included state DOTs and industrial partners.

In addition to these research projects, RMRC also has funds to assist state DOTs and state EPAs with small, but specific, research problems associated with the use of recycled materials. States with specific research problems can apply to the center, and the center may either conduct the research itself on the state’s behalf or may turn to other national experts to undertake the research. This funding is available now, and states with recycling-related research needs are urged to contact RMRC about the possibility of accessing these resources.


A number of outreach activities have taken place during the nearly two years since the opening of the center, and more are planned for the near future., which was launched on Feb. 15, 1999. A key component of the center’s mission is keeping the highway community up to date about developments in the field of recycled materials use, upcoming events, resources, ongoing RMRC activities, and so forth. By filling out a simple online form, the Web page provides a route for users to officially register with, and become a client of, RMRC. There is no obligation in becoming an RMRC client, and the service is provided free of charge.

RNRC Web Site

One of the principal information and outreach mechanisms for the center is its Web site ( Center clients are routinely given up-to-date, topical recycling-related information and activities, and they may directly benefit from all that the center has to offer. This includes access to an information request feature, updates on ongoing research projects, information about eligibility to receive funding for research projects, request for research proposal information, an expanding technical library, virtual demonstration sites, information about eligibility for technical support services, information about upcoming training courses, an online discussion forum, and much more.

Also featured on the RMRC Web site are links to international, federal, state, association, corporate, and university Web sites and to state-specification Web pages. RMRC’s research projects are also featured, and these are updated periodically as progress is made. The site also contains a link to the FHWA database titled "User Guidelines for Waste and Byproduct Materials in Highway Construction." Information about RMRC’s mission and goals, articles about the center, related center research publications, and copies of presentations made by RMRC personnel may also be found on the Web site.

Electronic Quarterly Newsletter

RMRC circulates an electronic newsletter to its clients each quarter. The specific purpose of the newsletter is to keep clients up to date concerning RMRC’s endeavors to promote the use of recyclable materials in the highway environment. In addition, the newsletter is a vehicle to promote ongoing research activities, events, and construction projects and to provide other information pertaining to the use of recyclable materials in highway construction applications. Indeed, feel free to contact the center with any topical information or personal insights that you would like to broadcast or share in future issues.

Virtual Demonstration Site

A virtual demonstration site has been established on the RMRC Web site. Viewers can visit recycled materials field demonstration projects and can look at photographs; video clips; report summaries; important summary data of laboratory and field testing; and lists of contacts, sponsors, and related publications. This is an extremely useful tool for all parties interested in learning more and in sharing experiences about actual projects using recycled materials. It also enables state DOT and state EPA personnel to visit demonstration sites and "kick the tires" right from their offices.

The virtual Web site is a relatively new feature. Currently, one project is featured: a municipal solid waste (MSW) bottom ash paving project. However, with the help of clients and other users, the site will be expanded so that many recycled materials and highway applications will be featured.