November/December
2001
Recent
Publications
Compiled
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 www.ntis.gov 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 www.tfhrc.gov, FHWA's
Web site at www.fhwa.dot.gov,
the National Transportation Library's Web site at http://ntl.bts.gov,
or the OneDOT information network at http://dotlibrary.dot.gov/.
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 www.tfhrc.gov/hnr20/00164.htm.
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.
Other
Articles in this Issue:
Legacy
of a Landmark: ISTEA After 10 Years
Creating
a Landmark: The Intermodal Surface Transportation Act of 1991
"Put
the Brakes on Fatalities" Day