Acoustic Emission Characterization of the Fracture Process in Fly Ash Fiber–Reinforced Asphalt Concrete

The main purpose of this study was to understand the failure mechanism of fly ash fiber–reinforced asphalt specimens under uniaxial compression loading and splitting loading, respectively. The variation of acoustic emission (AE) parameters in the acoustic emission tests during this fracture process was analyzed. The results showed that under uniaxial compression, the failure process of the fiber asphalt specimens could be divided into four stages: the formation of internal microcracks, microcrack propagation, rapid crack propagation, and finally, failure. Shear failure is the main failure form of asphalt specimens, and with the gradual increase of fiber content, the failure mode of specimens gradually changes from shear failure to shear-tensile failure. The correlation analysis between peak value and frequency of acoustic emission parameters shows that there are three frequency bands of fly ash fiber asphalt specimen, namely, 0–30, 30–60, and 150–200 kHz, which correspond to the initial dislocation failure of the interface between aggregate and asphalt mortar, the fracture failure of the interface between fly ash fiber and asphalt mortar, and the complete dislocation failure of the interface between aggregate and asphalt mortar.