Precursors for detecting impending fracture in cementitious composites using natural time analysis of acoustic emission

This article presents the application of natural time analysis of acoustic emission (AE) to detect impending fracture in ultra high performance concrete (UHPC).The UHPC beams with and without coarse aggregate were made and subjected to a three-point bending test.Simultaneously, the generated AE were recorded using an eight channel AE monitoring system.The parameters, namely, variance ( 1 ), entropy (S), and entropy under time reversal (S ), were studied in natural time domain.All these parameters simultaneously reached their critical values and fluctuated within the time window corresponding to the region of criticality.The critical conditions of the parameters were accompanied by a significant increase in cumulative AE energy, which resembled the Olami-Feder-Christensen earthquake model.Furthermore, change in entropy (S) was minimized before the mainshock event, thus indicating the imminent major event.Therefore, 1 , S, S , and S could be utilized as precursors for detecting impending macroscopic fracture in cementitious composites.