Investigation of fracture modes in pervious asphalt under splitting and compression based on acoustic emission monitoring

Abstract

Fracture behavior of asphalt mixture due to load and environment conditions is associated with the service life of asphalt pavement. Characterization of fracture modes in asphalt mixture is a challenging topic, especially for pervious asphalt (PA) with non-uniform gradation and large air void (VV). The purpose of this study was to demonstrate the fracture modes of PA under compression and splitting based on acoustic emission (AE) monitoring. Uniaxial compression testing, splitting testing and AE monitoring were carried out simultaneously on cylinder PA specimens. AE parameters including average frequency (AF) and rise angle (RA) were obtained and used to characterize the variations of fracture modes with load levels. Fracture modes were classified and interpreted through correlation analysis between RA and AF combined with k-medoids clustering analysis. Temperature effects on fracture modes of PA were also considered and demonstrated. The results revealed that shear and tensile cracks coexisted and presented similar propagation trends during compression and splitting testing. RA exhibited upward trend and AF presented downward trend at the final failure stage of compression test, while an opposite phenomenon was observed for splitting test. k-medoids clustering realized the identification of cluster centers of shear and tensile cracks, which was beneficial for fracture mode characterization. As testing temperature rises, RA and AF for PA specimen under compression and splitting testing all decreased. In splitting test, the decrease of RA is greater than that of AF. In compression test, the decrease of AF was larger. The findings obtained in this study can provide references for understanding fracture mechanism and real-time fracture monitoring of PA pavement under complicated conditions.