Comparison of two low-temperature cracking tests for use in performance-based asphalt mixture design

Abstract

ABSTRACT Cracking is one of the main causes requiring replacement of asphalt pavement, but the traditional mix design methodologies do not require testing of asphalt mixture cracking resistance. Two cracking tests, Thermal Stress Restrained Specimen Test (TSRST) and Semi-Circular Bending (SCB), were evaluated in this study to determine their suitability for adapting as part of mixture type testing and quality control protocol. Eight different mixtures were used to evaluate the test methods, having a wide range of maximum aggregate size, mix type, binder grade and target application. Half of the mixtures were plant-produced, while the other half were laboratory-produced. The results showed that TSRST is the preferred method for mix design because of smaller result variability and better distinguishing between the different mixtures. At the same time, a reasonable correlation exists between TSRST and SCB tests. This makes it possible to use the simpler SCB test for pre-screening samples to further test using the TSRST. The equivalent ageing protocol is a pre-requisite to be able to compare the test results. The fraass breaking point, a measure of bitumen low-temperature cracking resistance, did not provide good correlation with either of the mixture cracking tests.