Experimental study on acoustic emission characteristic of fatigue crack growth of self-compacting concrete

In order to study the fatigue crack growth (FCG) of self-compacting concrete, in this paper, the 100mmx100mmx400mm specimens with a 30-mm initial notch were used for three-point bending test under three different stress levels (0.75, 0.8, and 0.85) and three different loading frequencies (0.5, 1, and 2Hz), and the acoustic emission (AE) technique was used for monitoring the FCG. According to the results, the changes of the crack mouth opening displacement, the stiffness, and the effective crack length all present three obvious stages with the increase of fatigue cycles. According to Paris law, under the same stress level, the increase of loading frequency results in the increase of fatigue life and the decrease of FCG rate, but the curves of da/dN are approximately parallel under different loading frequencies. Furthermore, the research results of characteristic parameters of AE show that cumulative hits, counts and energy show three stages, which are similar to the change of stiffness, and there is a failure point in the curves of cumulative counts and cumulative energy. The cumulative laws of hits and counts can be used to well describe the FCG, and the b value can be used to analyze the three stages of fatigue fracture. Therefore, the AE technology can be used to monitor the FCG in concrete engineering.