Experimental study on mechanical properties of precast cracked concrete under different cooling methods

Abstract In order to investigate the mechanical properties and crack propagation of concrete after high temperature, the concrete specimens with different angles of prefabricated cracks are treated with different high temperatures and different cooling methods and then subjected to uniaxial compression. The T2 spectrum is performed on the concrete that has experienced different high temperatures to detect its pore changes. Acoustic emission is used to monitor the destruction process of the concrete during the test. The composition of the damaged specimen by scanning electron microscope and X-ray diffraction are analyzed, then the relationship between the stress–strain curve, porosity change and macroscopic and microscopic properties of concrete are compared and analyzed. In this study, a certain range of high temperature significantly increased the uniaxial compressive strength of concrete. Then, the uniaxial compressive strength decreased rapidly when the temperature is higher than a certain level. It is observed that the bonding degree of concrete aggregate and cement inside the damaged specimen is different after high temperatures and cooling methods treated by using scanning electron microscope. The damage degree of concrete caused by high temperature and water cooling is far greater than that of air cooling. The acoustic emission signal and energy release between the normal temperature specimen and the specimen after high temperature treatment in the test process are quite different. This paper explains the mechanical phenomena of cracked concrete specimen after being treated with high temperature and different cooling methods from the microscopic and mesoscopic perspectives.