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

Abstract

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. In recent years, acoustic emission technology has been widely used in the field of nondestructive testing of cement concrete and bridge structures. Nevertheless, the damage identification methods commonly used in asphalt pavement, such as the computational simulation method and image processing method, have low working efficiency, large error, and lack of dynamic perception of the whole damage process, which limits their applicability in practical engineering applications. In this paper, acoustic emission technology has been employed to characterize the damage and crack propagation law of fiber asphalt specimens under various stress states. Through the analysis of the evolution characteristics of acoustic emission signal parameters, the fracture damage characteristics of fiber asphalt samples under different stresses are invested. The research results are of great significance for the popularization and application of acoustic emission technology in the field of nondestructive testing of asphalt pavement.