Performance assessment of basalt fiber reinforced foamed concrete under freeze-thaw conditions using advanced acoustic emission parameters

Advanced acoustic emission (AE) parameters have great potential for structural health monitoring of foamed concrete (FC) materials. In order to investigate the mechanical properties and damage evolution laws of basalt fiber-reinforced foamed concrete (BFFC) under freeze-thaw conditions, combined AE-uniaxial compression tests were carried out on specimens with three different fiber contents and four different numbers of freeze-thaw cycles. The advanced AE parameters applicable to BFFC were determined with the help of principal component analysis, and the damage law was analyzed and evaluated with the uniaxial compression loading data. The results indicate that the failure modes of BFFC mainly consist of three types: matrix cracking, fiber/matrix debonding, and fiber fracture. With an increase in fiber content, the failure mode of FC transitions from the coexistence of three types to extensive matrix cracking, accompanied by a decrease in the activity of AE signals, demonstrating the positive effect of basalt fibers (BF) on enhancing toughness. Additionally, a novel FC damage crack discrimination technique proposed based on the Kneedle algorithm can effectively distinguish between tensile cracks and shear cracks. Based on AE signals and uniaxial compression test data, the correlation between load-ringing count-accumulated ringing count, load-energy-accumulated energy, and load-peak frequency was analyzed. The results show that AE signals can effectively evaluate the damage evolution law of BFFC. The compression failure process can be divided into three stages: fiber reinforcement stage, specimen failure stage, and load-bearing moderation stage. Furthermore, with an increase in freeze-thaw cycles, the initial damage inside the specimen increases. Under sustained loading, the bearing capacity of FC decreases, and the AE signal parameters exhibit a decreasing and attenuating trend.