Fracture Monitoring of SBS and Crumb Rubber Modified Porous Asphalt Mixtures under Compression and Splitting Testing Using Acoustic Emission Technique

An acoustic emission (AE) approach to evaluate the fracture process of porous asphalt mixture (PAM) under compression and splitting testing at different temperatures is presented. Two kinds of PAM, styrene-butadiene-styrene (SBS)-modified porous asphalt mixture (SBSPAM), and crumb rubber and SBS compound-modified porous asphalt mixture (CR/SBSPAM), were investigated and corresponding failure load and AE parameters were obtained. Damage assessments of PAM under compression and splitting testing were carried out using relative AE hits and energy. AE hits and energy had negative correlation with failure load. Damage processes of PAM under compression and splitting testing can be classified into three stages based on variation trends of relative AE hits and energy with load level. The softening effect caused by high temperature can lead to acoustic activity of SBSPAM under compression at a low load level, and the addition of CR can reduce the AE activity caused by the softening effect by improving the temperature susceptibility of binder. Change curves of relative AE hits and energy of CR/SBSPAM are more uniform than those of SBSPAM because of the more stable structure improved by CR modification. The findings of this study can provide references for damage evaluation of PAM using the AE technique.