Acoustic Emission Analyzing the Crack Classification and Damage Evolution on Stainless Steel Rebar Reinforced Geopolymer Coral Aggregate Concrete Beam

The production of geopolymer coral aggregate concrete beam (GCACB) effectively addresses concerns regarding limited concrete raw materials and structural erosion in island construction. Acoustic emission technology (AE) is an appealing solution for non-destructive evaluation and structural health monitoring. In this study, 6 specimens of GCACB were designed with different reinforcement ratios for the four-point bending test, simultaneously recording the corresponding AE data. Then, the effect of each AE parameter on crack development was analyzed, and the crack pattern classification was investigated utilizing the GMM algorithm. Finally, the GCACB damage was evaluated based on two different AE b-value methods. The results show the cracks within GCACB predominantly occur along the coral coarse aggregate with low strength and high brittleness. The presence of reinforcement ratio has an enhancement on both the flexural capacity and deformation capacity of GCACB while impeding the crack width. A positive correlation between increasing crack damage and the cumulative hits, ringing counts, and AE energy occurs. The enhanced GMM method establishes a probabilistic division line for the RA-AF relationship that progressively leans towards the AF axis as the reinforcement ratio increases. This signifies an augmentation in tensile cracks with an increasing reinforcement ratio. In contrast to b-value obtained from GBR method, the Aki method demonstrates enhanced predictive capability for GCACB damage. Additionally, the b-value in a stably-low state is a likely precursor to the failure of GCACB.