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Low temperature cracking is attributed to tensile stresses induced in an asphalt concrete pavement that develop when the pavement is subjected to a cold temperature. Cracking results in poor ride quality and a reduction in service life of the pavement. Low temperature cracking has been predicted by regression equations, mechanistic approaches and by simulation measurements. The purpose of the study reported herein is to (1) evaluate the Thermal Stress Restrained Specimen Test (TSRST) as an accelerated performance test to simulate low temperature cracking of asphalt concrete mixtures and (2) develop a deterministic and probabilistic model to predict low temperature cracking with TSRST results. Construction histories, cracking observations and temperature data were collected for five test roads in Alaska, Pennsylvania and Finland. A full scale and fully controlled low temperature cracking test program was conducted at the U.S. Army Cold Regions Research and Engineering Laboratory (USACRREL). Specimens were fabricated in the laboratory with original asphalt cements and aggregates from the test roads. In addition, asphalt concrete pavement specimens were cut from the test sections. The TSRST results obtained for these samples were correlated with the field observations. Based on a statistical analysis of the data, the TSRST fracture temperature is associated with the field cracking temperature and crack frequency for the test roads where mixture properties dominated low temperature cracking. It was concluded that the TSRST can be used to simulate low temperature cracking of asphalt concrete mixtures. A deterministic and a probabilistic model were developed to predict crack spacing as a function of time using the TSRST results, pavement thickness and bulk density, pavement restraint conditions and air temperature. The affect of aging on pavement properties was incorporated in the models by predicting the field aging with Long Term Oven Aging (LTOA) treatment in the laboratory. The calculation of the crack spacing is based on the theory that the pavement slab cracks when the pavement temperature reaches the cracking temperature of the mixture and the slab is fully restrained. The deterministic model predicts crack spacing with time whereas the probabilistic model predicts crack spacing and its variation with time and yields the reliability of the design with regard to a minimum acceptable crack spacing criterion defined by road authorities. The models were verified by comparing the predicted crack spacings for the five test roads to the observed crack spacings. The probabilistic model is recommended for use in predicting the low temperature cracking of asphalt concrete mixtures.
The purpose of the field validation program was to evaluate the thermal stress restrained specimen test (TSRST) as the accelerated performance test to predict low-temperature cracking of asphalt concrete mixtures. Construction histories, cracking observations, and temperature data were collected for five test roads. In addition, a validation program was conducted at the United States Army Cold Regions Research and Engineering Laboratory. The laboratory test program consisted of performing the TSRST on specimens fabricated in the laboratory with original materials from the test roads and asphalt concrete pavement specimens cut from the actual test sections. In addition, the field pavements were monitored for crack history and, where possible, crack initiation. TSRST fracture temperature correlated with field cracking temperature and crack frequency. TSRST results can be used to predict field low-temperature cracking of asphalt-aggregate mixtures. Preliminary models to predict cracking frequency and temperature for the test roads were developed.
This report describes the thermal stress restrained specimen test (TSRST), which was selected to evaluate the low-temperature cracking resistance of asphalt concrete mixtures. The TSRST system includes a load frame, step-motor-driven load ram, data acquisition hardware and software, temperature controller, and specimen alignment stand. An experiment design that considered a range of mixture and test condition variables was developed to evaluate the suitability of TSRST for characterizing low-temperature cracking resistance of asphalt concrete mixtures. Four asphalts and two aggregates were selected for the experiment. The mixture variables included asphalt type, aggregate type, and air voids content; the test condition variables included specimen size, stress relaxation, aging, and cooling rate.
This report examines the feasibility of using the thermal stress restrained specimen test to evaluate low temperature cracking in asphalt pavement mixes. Data were collected from laboratory and field evaluations. Various mixing, aging, and compaction methods were used to prepare test samples with materials obtained from two Wyoming Department of Transportation (WYDOT) highway projects. Field data were obtained from two recently built test sections and compared with laboratory test results. Pavement condition surveys quantified low temperature cracking of both test sections after one winter. Temperature data for the project sites also were collected. Pavement condition and temperature data were compared to results from the thermal stress restrained specimen test. The thermal stress restrained specimen test was effective in testing asphalt pavement mixes. However, test results indicated that lab prepared samples did not closely simulate field samples. Also, comparisons of lab results with field conditions were performed. However, it is recommended that a more comprehensive analysis be performed after test sections have been in service for a few years.
A study was performed to determine the influence of material properties on the thermal cracking performance of hot mix asphalt (HMA), and to determine the ability to predict thermal cracking from pavements of known field performance. The testing device used to measure the HMA properties was the thermal-stress, restrained-specimen test (TSRST), and the device used to measure the binder properties was the bending beam rheometer (BBR). The laboratory study was conducted to determine the variability of test results as an influence of 1) asphalt cement stiffness, 2) asphalt cement quantity, 3) mixes with various aggregate qualities, 4) aging, and 5) the presence of hydrated lime. The influence of the asphalt cement stiffness was the single largest factor that controlled the test results.
Internationally, much attention is given to causes, prevention, and rehabilitation of cracking in concrete, flexible, and composite pavements. The Sixth RILEMInternational Conference on Cracking in Pavements (Chicago, June 16-18, 2008) provided a forum for discussion of recent developments and research results.This book is a collection of papers fr
A thermal stress restrained specimen test (TSRST) was developed to determine the thermal, or the low-temperature cracking resistance of asphalt concrete mixes. The test system is capable of cooling an asphalt concrete specimen at a constant rate, while restraining the specimen from contraction and periodically measuring elapsed time, specimen surface temperature, and tensile load. TSRST's were performed on both short- and long-term aged specimens. Statistical analyses were performed on the test results. Rankings of asphalt concrete mixtures based on fracture temperature were compared to rankings based on fundamental properties of the asphalt cement.
Analysis of Pavement Structures brings together current research and existing knowledge on the analysis and design of pavements and introduces load and thermal stress analyses of asphalt and concrete pavement structures in a simple and step-by-step manner. For the second edition of this book, a new chapter on numerical implementation (using FEM) of pavement analysis is added along with topics such as mechanical modeling of granular materials, applications of convolution theorems in visco-elasticity, visco-elastic Poisson’s ratio, concepts of fracture mechanics in relation to fatigue of asphalt mix, solution of semi-infinite and so forth. New solved examples and schematic diagrams are also added. Features: Presents a simple, step-by-step approach for pavement analysis including systematic compilation of research work in the area Discusses further elaborations in terms of extended analytical formulations on some selected topics Includes new chapter on finite element analysis for pavement structures Contains more solved examples to understand the concepts better Explores primary application of pavement analysis in pavement thickness design This book is aimed at graduate students, structural mechanics researchers, and senior undergraduate students in civil/pavement/highway/transport engineering.