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WesTrack was a hot-mix asphalt (HMA) accelerated pavement test (APT) facility located in the State of Nevada approximately 100 km (60 mi) southwest of Reno, Nevada.
The pavement test facility was designed, constructed, and operated by a team of private companies and universities (WesTrack team) under contract to the Federal Highway Administration (FHWA) and the National Cooperative Highway Research Program (NCHRP) from September 1994 through September 2000.
The original contract for the research project was awarded in September, 1994.
The test track was designed and constructed during the period between October 1994 and October 1995 and was subjected to traffic from March 1996 through
February 1999.
The project had two primary objectives as follows:
Continue the development of performance-related specifications (PRS) for HMA pavements by evaluating the impact on performance of deviations in materials and construction properties (asphalt binder content, aggregate gradation, aggregate type and in-place air void content) from design target values.
Provide an early field verification of the SHRP Superpave HMA volumetric design method.
The scope and objectives of the study directed the study to consider two primary types of HMA pavement distress: permanent deformation or rutting and fatigue cracking. Thickness design and HMA mixture design considerations were largely directed to developing a facility and mixture that would rut and fatigue crack during the life of the experiment.
Track maintenance activities including surface patching, dig-out and replace patches, milling and filling with HMA took place during the life of the facility.
Ten of the 26 test sections (i.e., sections 5, 6, 7, 8, 9, 13, 21, 24, and 26) on the 3-km (1.8-mi) oval track were replaced in June of 1997.
For eight of those ten replacement sections, a study was developed to better define the effect of aggregate characteristics in coarse-graded
Superpave mixtures on pavement performance (primarily permanent deformation or rutting). The replacement sections were “coarse”
graded mixtures and duplicated (on a relative basis) the asphalt binder content and in-place air void content of the “coarse” graded
mixtures placed during the original construction. The section numbers used to describe the coarse-graded mixtures assumed that section 1
of the originally constructed track would become section replacement 31 of the replacement section track. Thus,
section 5 (an original construction “coarse” graded mixture) became section 35 of the replacement sections.
There were a total of eight replacement sections under Superpave phase of the WesTrack experiment,
which were sections 35, 36, 37, 38, 39, 54, 55, and 56.
Approximately 5 million 80-kN (18,000-lb) equivalent single axle loads (ESALs) were applied to the track during the WesTrack experiments.
Throughout the WesTrack project, a substantial amount of data was collected, summarized, and stored in electronic format in organized directories and files. Data collection and processing protocols from the Long-Term Pavement Performance (LTPP) program were extremely beneficial to the entire WesTrack experiment. The NCHRP Web-Only Document 111, which is one of the reports listed under the "Library" module, has a series of technical reports that also cover the WesTrack data collection and analysis procedures and refer to the LTPP protocols when utilized.
The data elements in the WesTrack database include the following:
Throughout, the WesTrack project performance data was collected at regular intervals and more frequently when certain circumstances warranted.
In total, performance data was collected on 49 occasions during the project.
In general, the following data was collected for each section during these occasions:
Severity and extent of fatigue cracking.
Severity and extent of raveling.
Severity and extent of bleeding.
Magnitude of rut depth, both maximum rut depth (peak to valley) and downward rut depth (baseline to valley).
Magnitude of roughness (smoothness).
All performance data collected has been summarized and included within the database.
Materials data
Materials data included information regarding aggregate properties, binder properties, and mixture properties. These data were collected at various stages throughout the project. The following is a list of the types of materials data collected and stored in the database.
Aggregate properties included in the database include the following:
Stockpile gradations.
Cold feed gradations.
QC/QA gradations.
Specific gravity and absorption.
Angularity.
Sand equivalent value.
Flat/elongated particles.
Soundness.
Soundness.
Deleterious materials.
Binder properties included in the database include the following:
Bending beam rheometry.
Dynamic shear rheometry.
Capillary viscosity.
Rotational viscosity.
Penetration.
Flashpoint.
Mixture properties included in the database include the following:
Repeated simple shear at constant height (RSST-CH) test.
Beam fatigue.
Thermal stress restrained specimen test (TSRST).
Moisture sensitivity of the HMA mixture.
Resilient modulus of the HMA mixture.
Resilient modulus of the base course.
Resilient modulus of the engineered fill.
Wheel tracking Laboratoires des Ponts et Chaussées (LCPC), Hamburg, Asphalt Pavement Analyzer, and Purdue devices.
Indirect tensile test.
Seasonal data
Seasonal data includes information regarding the depth of the groundwater table and the subgrade soil moisture content. This information was collected at approximately the same intervals as the performance data.
The groundwater depth was measured using piezometers located adjacent to sections 12 and 25. The measurements obtained from the piezometers were translated (adjusted) to represent the depth of the water table below the centerline of the test lane at the test track.
Time-domain reflectometry measurements were obtained from probes located adjacent to sections 12 and 25. These data were then reduced using the protocol established for and used within the Long-Term Pavement Performance (LTPP) program to estimate the moisture content within the subgrade soil.
Weather data
Weather data was collected on a continuous basis from an on-site weather station throughout the duration of the project. The type of data collected and included in the database included the following:
Air temperature.
Humidity.
Wind speed and direction.
Precipitation.
Solar radiation.
Pavement temperature.
All performance data collected has been summarized and included within the database.
Traffic data
Traffic loading was induced by four triple trailer trucks weighing approximately 70,000 kg. (154,000 lbs.) each. Each truck pass applied approximately 10.49 ESALs to the track. Driverless technology was used to guide the trucks around the track. The trucks followed a guidewire embedded within the asphalt layer in the middle of the test lane. Each of the driverless trucks followed a simulated traffic wander similar to real highway traffic. WesTrack traffic data contains information on total daily ESALs for all trucks, whether a truck was operated by a driver on a particular day, individual truck daily ESALs, and the date of the recorded operation.
WesTrack data has not been collected by the LTPP program.
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