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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 - November/December 2001

Communication Product Updates

Recent Publications

by Zac Ellis of FHWA's Office of Research and Technology Services

Below are brief descriptions of reports recently published by the Federal Highway Administration's (FHWA) Office of Research, Development, and Technology. All of the publications are available from the National Technical Information Service (NTIS). In some cases, limited copies of the publication are available from the Research and Technology (R&T) Report Center.

When ordering from NTIS, include the NTIS PB number (or publication number) and the publication title. You may also visit the NTIS Web site at to order publications online. Call NTIS for current prices. For customers outside the United States, Canada, and Mexico, the cost is usually double the listed price. Address requests to:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Telephone: (703) 605-6000

Toll-free number: (800) 553-NTIS (6847)

Expanded Sales Desk Hours: 8 a.m. to 8 p.m. EST, Mon.-Fri.

Requests for items available from the R&T Report Center should be addressed to:

R&T Report Center, HRTS-03

Federal Highway Administration

9701 Philadelphia Court, Unit Q

Lanham, MD 20706

Telephone: (301) 577-0906

Fax: (301) 577-1421

For more information on research and technology publications coming from FHWA, visit the Turner-Fairbank Highway Research Center's (TFHRC) Web site at, FHWA's Web site at, the National Transportation Library's Web site at, or the OneDOT information network at

A Predictive Approach for Long-Term Performance of Recycled Materials Using Accelerated Aging

Volume I: Final Report

Volume II: Appendices

Publication Nos. FHWA-RD-01-022 and -023

The use of recycled materials in a proposed highway application frequently requires the assessment of physical and environmental performance. Future behavior is often difficult to predict. As an alternative to field demonstrations, there is a need to develop strategies to predict long-term physical and environmental performance. Accelerated aging is one means of exploring the long-term physical and environmental performance of recycled materials in a highway.

Coal fly ash use in portland cement concrete (PCC) was selected as a model system to develop an accelerated aging approach. Three types of accelerated aging were chosen for this project: Arrhenius aging, cyclic loading, and freeze-thaw exposure. This approach, incorporated in an experimental design, allowed a systematic exploration of the separate effects and combined interactions of both developmental and degradative accelerated aging variables. A slab from U.S. Route 20 in northwest Iowa was used as both the basis for the concrete mixes and as a field verification site.

The NTIS publication number is PB2001-107670 for volume I and PB2001-107671 for volume II.

Highway Effects on Vehicle Performance

Publication No. FHWA-RD-00-164

A user-friendly model for personal computers, "Vehicle/Highway Performance" was developed to estimate fuel consumption and exhaust emissions related to modes of vehicle operations on highways of various configurations and traffic controls. It is intended for highway designers and planners, and strategists optimizing Intelligent Transportation Systems. The model simulates operations of vehicles by evaluation of the vehicle external loads or propulsive demands, which are determined by longitudinal and lateral accelerations, positive and negative road grades, rolling resistance, and aerodynamic drag for various transmission gears. The computations of fuel consumption and air pollutant emissions are then related to the vehicle maps of fuel consumption and air contaminant emission rates as evaluated from large-roll dynamometer measurements for vehicle operations under various loads, speeds, and transmission gears or as may be estimated based on engine maps, speeds, loads, and vehicle drive-train characteristics.

The NTIS publication number is PB2002-100122. The publication is also available in PDF format at TFHRC's Web site at It is divided into small files for easier downloading and printing.

The Effects of Higher Strength and Associated Concrete Properties on Pavement Performance

Publication No. FHWA-RD-00-161

The major goal of this project was to develop recommendations for PCC properties and materials characteristics found in higher strength jointed plain concrete pavements (JPCP) with improved long-term performance as determined by joint spalling and faulting, and transverse slab cracking. Primary project variables were pavement age, climate, traffic (4 to 23 million equivalent single-axle loads [ESALs]), distress levels and types, joint spacing, and compressive strength. Fifteen JPCPs were selected for detailed field and laboratory investigation. The field compressive and tensile strengths (splitting) ranged from 33 to 75 MPa and from 3.1 to 4.5 MPa, respectively.

The NTIS publication number is PB2001-107672.

Microdamage Healing in Asphalt and Asphalt Concrete

Volume I: Microdamage and Microdamage Healing, Project Summary Report

Publication No. FHWA-RD-98-141

Volume I is a summary report that chronicles the research highlights of the entire study of microdamage healing in asphalt concrete. The primary objectives of the study were to: (1) demonstrate that microdamage healing occurs and that it can be measured in the laboratory and in the field, (2) confirm that the same fracture properties that control propagation of visible cracks control the propagation of microcracks, (3) identify the asphalt constituents that influence microdamage and microdamage healing, (4) establish appropriate correlations between microdamage and microdamage healing in the laboratory and in the field, and (5) predict the effects of microdamage healing on pavement performance and develop the appropriate constitutive damage models that account for the effects of microdamage healing on the performance of asphalt concrete pavement layers. Volume I describes the success of the project in obtaining each research objective.

The NTIS publication number is PB2001-107666.

Microdamage Healing in Asphalt and Asphalt Concrete

Volume II: Laboratory and Field Testing to Assess and Evaluate Microdamage and Microdamage Healing

Publication No. FHWA-RD-98-142

Volume II documents laboratory and field testing that provides the evidence that microdamage healing is real and measurable and that it has a significant impact on pavement performance. Part of the laboratory experiments to evaluate the impact of rest periods was performed at North Carolina State University. The experiment included two very different asphalt binders: AAD and AAM. The experiment clearly demonstrated that the rest periods introduced after fatigue damage allowed significant recovery in the flexural and dynamic modulus. The recovery was attributed to the healing of microcracks within the sample. A separate series of laboratory testing was performed at Texas A&M University's Texas Transportation Institute. These tests consisted of controlled-strain haversine loading direct tensile tests and controlled-strain trapezoidal loading direct tensile tests.

This volume completes the evidence of microdamage healing with convincing field evidence. Wave speed and attenuation measurements were made on in situ pavements. The stress wave test and analysis successfully detected fatigue damage growth and microdamage healing of asphalt pavements (at the Accelerated Loading Facility at FHWA's Turner-Fairbank Highway Research Center) with different asphalt layer thicknesses and viscosities, and demonstrated the importance of microdamage healing during rest periods of pavement performance. The ability of stress wave testing to measure microdamage and healing in the field was further evaluated at the Minnesota Road Project on seven pavement test sections at the site.

The NTIS publication number is PB2001-107667.

Microdamage Healing in Asphalt and Asphalt Concrete

Volume III: A Micromechanics Fracture and Healing Model for Asphalt Concrete

Publication No. FHWA-RD-98-143

Volume III documents the development of a micromechanics fracture and healing model for asphalt concrete. This model can be used to calculate the density and growth of microcracks during repeated direct tensile controlled-strain loading. The model is based on a relationship among stiffness changes in the mixture as damage occurs; the rate of change in dissipated pseudo-strain energy as loading is applied to the samples and as damage occurs; and mixture properties, including crack length changes upon loading and mixture cohesive surface energies. The report demonstrates that microcrack growth is the dominant mode of distress at temperatures below 25oC and that microcrack healing is the dominant mode of recovery of dissipated pseudo-strain energy at these test temperatures. However, at temperatures above about 25oC, the predominant mode of distress is plastic damage.

The NTIS publication number is PB2001-107668.

Microdamage Healing in Asphalt and Asphalt Concrete

Volume IV: A Viscoelastic Continuum Damage Fatigue Model of Asphalt Concrete With Microdamage Healing

Publication No. FHWA-RD-98-144

Volume IV presents a mechanistic approach to fatigue characterization of asphalt-aggregate mixtures. This approach is founded on a uniaxial viscoelastic constitutive model that accounts for damage evolution under cyclic loading conditions. The elastic-viscoelastic correspondence principle is applied to evaluate damage growth and healing cyclic loading separately from time-dependent characteristics of the material. The damage growth during loading cycles and healing during rest periods are modeled using work potential theory (a continuum damage theory based on the thermodynamics of irreversible processes). Internal state variable formulation was used in developing the analytical representation model. Tensile uniaxial fatigue tests were performed in the controlled-strain mode with different strain amplitudes to determine model parameters. The resulting constitutive model successfully predicts the damage growth of asphalt concrete under monotonic loading at varying strain rates and damage growth.

The fatigue lives of two different mixtures were predicted with reasonable accuracy using the constitutive model for the constant stress-strain amplitude cyclic loading histories with and without rest periods. A standard uniaxial fatigue test protocol is proposed by simplifying the experimental approach used in developing the constitutive model.

The NTIS publication number is PB2001-107669.