Investigating thermal cracking potential of Ontario RAP-HMA mixtures

Thermal cracking on flexible pavements poses serious concerns in cold-regions of the world, especially in Canada. Influenced by temperature changes, thermal cracks are known to initiate other forms of pavement deterioration. The prevention of thermal cracks would guarantee better performance of roads built with asphalt concrete mixtures. Recognizing asphalt recycling as a key sustainable practice in the pavement industry, this paper examines the low-temperature cracking resistance of four dense-graded laboratory-prepared Ontario Superpave asphalt concrete mixtures. The asphalt mixtures were produced with 0%, 20% and 40% Reclaimed Asphalt Pavements (RAP) contents and three different binder grades. The low-temperature cracking resistance has been determined using the Thermal Stress Restrained Specimen Test (TSRST) method. The effects of different binder grades and RAP contents on the fracture stress and fracture temperature of the asphalt mixtures have been mainly investigated. Moreover, the influences of air voids content, binder aging, aggregate interaction, and laboratory compaction method have been observed. Test results revealed that binder grade and RAP content did not significantly affect the fracture resistance of asphalt mixture. These results are encouraging and demonstrate the value of TSRST as an important test for material characterization.