Dynamic compressive behaviors of high-temperature-cement mortar specimen subjected to different cooling methods

Abstract

Impact load and rapid cooling, which frequently appear in fire-fighting and explosion, are major factors to affect the stability of cement mortar structures. By carrying out the dynamic compressive and scanning electron microscope experiments on high-temperature-cement mortar specimen subjected to rapid cooling with different cooling methods, the dynamic compressive behaviors and internal structures were studied and discussed. The results show that both the strain and cooling rates affect dynamic properties. In details, dynamic compressive strength, which could be calculated by linear Function with strain rate, shows an increase trend when strain rate and cooling rate increase. On the contrary to the change of strength, the size of failure pieces decreases. The specimen breaks more thoroughly with increasing strain and cooling rates. The dynamic elastic modulus, which shows an decrease trend accordingly as cooling rate increases, shows inconspicuous change with strain rate. Comparison with untreated specimen, there are more failure paths during the compressive process, especially, when the specimen is treated with rapid cooling, the phenomenon is more evident. The thermal stress caused by cooling leads to the increasing size and number of cracks, even the cracks connecting with each other and forming into crack-system, which finally results in the weakening of dynamic properties.