In Situ Acoustic Emission Investigation of Asphalt Fracture Process and Damage Quantification for Different Asphalt Mixtures

The identification of cracking damage and the dynamic diagnosis of damage evolution are of great importance to prolong the service life of asphalt mixture materials. Acoustic emission (AE) can identify the formation and propagation of cracks by detecting the released energy of the damage; therefore, it provides a viable real-time technique to estimate the damage state in the context of structural health monitoring. In this study, the crack formation and propagation of three different asphalt mixtures were investigated using in situ AE monitoring and microscopy imaging. A three-point bending test was performed using specimens fabricated from three different types of asphalt mixtures. The variation of AE parameters such as the cumulative AE energy and the AE count was obtained and correlated with the crack sizes to characterize the damage process of the three mixtures. Based on the AE parameters, the whole damage process can be divided into three distinct phases, namely, the elastic deformation, damage accumulation, and crack propagation. The AE parameters in the three different mixtures show unique features, and they can be used to capture the transition between phases and identify the damage state. A universal power law model is proposed to correlate the AE energy and the crack density for different types of asphalt mixtures, providing a viable means for damage quantification and predictive maintenance.