The Study Of Concrete Temperature Damage Mechanism Under Different Cooling System

Fire accident is one of the main disasters that pose threat to personal and property safety and building collapse in the process of fire fighting will endanger the life of the trapped people and rescue workers. As the main building materials, concrete is widely used in all kinds of civil, industrial and transportation architecture. The studies on the performance of concrete under high temperature have been made massively and they are mainly concentrated on the concrete heating and natural cooling process. However, the research on how the fire water-jetting cooling effect influences concrete is almost blank. Based on the combination of experimental study and numerical simulation method, the damage mechanism of concrete under different cooling systems are studied. In this paper, the main content includes the following parts:(1)By doing the natural cooling and water-jetting cooling tests on the ordinary concrete, cellulose fiber concrete, copper-plating microfilament steel fiber concrete in different temperature, we observed the surface damage of the concrete specimens and tested residual mechanical strength. By comparing the results of these two cooling effects, waterjetting cooling could damage concrete leading to the decline of its mechanical strength was concluded. Comparing the extent of damage of these three kinds of concrete, the performance of copper-plating microfilament steel fiber concrete was better than other concrete in residual mechanical strength and damage degree which proved its excellent properties under waterjetting cooling.(2)Studied the influence of the shooting period and pressure to the effect of waterjetting cooling by controlling factors. It showed that when temperature goes up to 600 centigrade, increasing shooting pressure and period leads to higher damage of appearance and mechanical strength,while the growth rate declines for the latter. When the temperature goes down to 400 centigrade, the residual mechanical strength of steel fiber concrete increases with longer shooting period for the reason of "secondary hydration".(3)Water-jetting cooling effect is the interaction of jet flow effect and thermal shock effect. By calculating impact force under different shooting pressure, we proved that pure jet flow effect will not damage concrete in high temperature and a dynamic thermal stress model is derived.(4)The simulation results of the temperature field and stress field under different temperatures and shooting pressure was corresponding to the experimental results which proved that the thermal shock effect is the main factor of concrete damage and the paper concluded the damage mechanism of water-jetting cooling. In the thermal shock and impact of the jet coupling, when temperature stress due to the heat shock in the concrete surface is greater than the tensile strength of concrete, concrete crack, while with coupling of shooting pressure, concrete burst or peel, causing concrete damage.