The macro-and meso-cracking characteristics of warm mix crumb rubber asphalt mastics before and after aging

Abstract

Asphalt mastics have an important influence on the performance of asphalt mixtures. To study the effect of thermo-oxidative aging on the cracking characteristics of warm mix crumb rubber asphalt mastics (WCRM) and hot mix crumb rubber asphalt mastics (HCRM), the digital image correlation (DIC) technology was applied to the single-edge notch bending (SENB) test of asphalt mastics. By analyzing the changes in the strain field during the whole loading process of test specimens, a new index for evaluating the meso-cracking characteristics of asphalt mastics was proposed. Comparing the load–displacement (L-D) curve and horizontal strain–time (Exx-t) curve of asphalt mastics, the cracking characteristics of asphalt mastics were analyzed from the perspective of combining macro- and meso-scale. The results of the SENB test and DIC test were verified by the bending beam rheometer (BBR) test of asphalt mastics and the contact angle measurement test of asphalt-limestone. The results indicated that during the cracking process of asphalt mastics, micro-cracks were formed before the peak load (P) and macro-cracks were formed after the peak load (P). The cracking resistance of two crumb rubber asphalt mastics was reduced after aging. WCRM had better cracking resistance than HCRM. The rheological parameters (m/S) of asphalt mastics and the adhesion work (Was) of asphalt-limestone had a good correlation with the macro- and meso-cracking indexes (fracture energy GIC, strain derivative E′t) of asphalt mastics. That is, applying the DIC technology to the SENB test to analyze the effects of aging and warm additive on the macro- and meso-cracking characteristics of crumb rubber asphalt mastics had a good reliability.