Evaluation of Temperature Associated Cracking in Asphalt Mixtures by Means of Performance-Based Laboratory Testing

Abstract

In this paper, new test methods for identification of low-temperature failure of asphalt are proposed. Low-temperature failure occurs when the stresses induced by restrained thermal shrinkage during cooling periods exceeds the tensile strength at the respective temperature. In order to specify test methods describing both (i) these in-service conditions of
flexible pavements and (ii) the underlying thermorheological behavior of asphalt, the four tests characterized by different thermal and mechanical loading are required:

1. The Tensile-Stress-Restrained-Specimen Test (TSRST) is used to simulate the inservice conditions of asphalt by restraining the deformation, while the temperature is
reduced by a pre-specified cooling rate;

2. The Uniaxial-Tensile-Strength Test (UTST) provides insight into the material resistance (tensile strength) at selected temperatures;

3. The Thermal-Shrinkage Test (TST) is used to specify the loading during cooling by determining the thermal shrinkage coefficient as a function of temperature; and,
finally,

4. Creep/Relaxation Tests (CTs/RTs) for identification of the viscoelastic behavior of asphalt at different temperatures.

In fact, the combination of all four tests is required to fully characterize the low-temperaturebehavior of asphalt when subjected to thermal and mechanical (tensile) loading. Based on the
obtained experimental results, key material parameters for ranking asphalts with regard to their low-temperature performance are critically reviewed. Moreover, the different test results
provide important insight for the development of material models for analysis-based prediction tools and enable the formulation of optimization parameters of low temperature
characteristics for mix design.