Crack propagation characterization of crumb rubber modified asphalt concrete using J-R curves

Abstract

J-Resistance curves serve as a robust tool in characterizing the entire crack propagation trend of materials. Nevertheless, thus far, investigations on J-R curves of hot mix asphalt (HMA) have been very limited leading to scarce knowledge of post-peak fracture of the mixtures. In this research, mode I single-edge notched beam (SE(B)) fracture testing of unmodified and crumb rubber (CR) modified asphalt concrete mixtures was conducted with continuous monitoring of crack extension during the tests at 0 °C, −10 °C, and −20 °C. Modified HMA beams were fabricated incorporating 10% and 20% CR with 3% warm-mix additive. The CMOD-based elastic–plastic J-integral was computed incrementally during the tests and the J-R curve of each mixture could be determined. The results indicated that reducing the temperature increases the crack blunting energy from 0 °C to −10 °C while reducing the extents of the transition zone within blunting to unstable crack propagation of the unmodified mixtures. The unmodified mixtures undergo an unstable crack propagation as early as the macro crack initiates in −20 °C. At the same time, the incorporation of CR, could increase the blunting fraction of the R-curves at each temperature. Of vital importance, it could be detected that a 20% crumb rubber modification resulted in a more significant stable crack growth zone in the mixtures while developing a progressively rising R-curve in the post-peak region than the flat state in the unmodified mixtures at severely low temperatures.