Research on Kaiser effect of acoustic emission in concrete subjected to bending after freeze-thaw

For hydraulic concrete structures in cold coastal areas, the frost resistance of concrete is critical. To determine the range of force applied to concrete during freeze-thaw cycling. In this study, the force on concrete during freeze-thaw cycling were investigated by performing a three-point bending test on concrete after freeze-thaw cycling and also monitoring the damage process of concrete using acoustic emission(AE). Firstly, based on the variation of AE parameters during concrete damage, the range of Kaiser effect points appearing during three-point bending loading was determined. Secondly, the G-P algorithm was used to calculate the correlated fractal dimension of AE. The results of the study showed that the mass and relative dynamic elastic modulus(RDEM) of concrete decreased linearly with the increase in the number of freeze-thaw cycles. The Kaiser effect of increased AE ringing counts and cumulative energy, and decreased correlated fractal dimension, was observed in the freeze-thawed concrete specimens during loading as the load increased. By comparing the two methods, it was found that the difference between the Kaiser effect points determined by the AE parameter method and the correlated fractal dimension method ranged from 0% to 14%. And the ratios between the force corresponding to the Kaiser effect points and the peak force are less than 0.8.