Experimental investigation of concrete fracture behavior with different loading rates based on acoustic emission

To study the effect of loading rate on the fracture behavior, three-point bending fracture tests of concrete with loading rates of 0.0001 mm/s, 0.001 mm/s, 0.01 mm/s and 0.1 mm/s were carried out, respectively. And acoustic emission (AE) technology was adopted for real-time monitoring. The results show that the unable toughness of concrete has obvious rate effect. Meanwhile, there are two obvious inflection points in the curve of cumulative AE hits and the cumulative ringing count with the change of time, one of which may represent the starting point of concrete boundary effect. The number of AE events can represent the crack width of concrete fracture. It is found that with the increase of loading rate, the crack width and ductility of concrete decrease, while the quantity of shear crack of concrete increases. By comparing the fracture energy of concrete with the AE cumulative energy, both of them increase with the increase of loading rate, indicating that the AE cumulative energy can represent the change of fracture energy under different loading rates. Finally, the failure forms under different loading rates are analyzed by the change of b value. Based on the above research, AE technology can be used to study the fracture failure under low loading rate. (C) 2019 Elsevier Ltd. All rights reserved.