Identification of bending fracture characteristics of cement-stabilized coral aggregate in four-point bending tests based on acoustic emission

Cement-stabilized coral aggregate (CSCA) can be used as a base material for roads and airports, and it is a future direction for island engineering. In this study, four-point bending tests were conducted on notched CSCA beams with different notch depth ratios, and the specimens were monitored using acoustic emission (AE) technology. The ringing count, amplitude, RA value, frequency, and b-value were used to study the bending fracture characteristics of the CSCA material. The results of the study showed that the 28d flexural tensile strength of the CSCA beam was 0.922 MPa when the test loading rate was 0.1 mm/min. The CSCA materials exhibited brittleness during the bending fracture process. The CSCA originally had defects, internal pores, and large-diameter irregular coral aggregates, which caused beam fractures from the weak surface near the loading point. At the stage where the peak force was reduced to approximately 0.2 times the peak force, many cracks in the CSCA formed, extended, and connected, and the beams experienced dense damage. The damage to the CSCA material was dominated by tensile cracks. In the CSCA material, the combined effect of the aggregate and cement paste was enhanced, the strength of the interfacial transition zone was increased, and the strength of the aggregate was weakened compared with that of cement-stabilized macadam material. The fracture process of the CSCA material was accompanied by the destruction of the interface and fracture of the aggregate particles.