Experimental Study On Mechanical Properties Of High Strength Concrete Sprayed With Water After High Temperature

High-strength concrete has high compressive strength,low porosity,high density,good compactness,impermeability and frost resistance due to ordinary concrete.The advantages of high-strength concrete make it easy to optimize the section,increase the space for building use,and reduce the weight of the structure.With the application of high-strength concrete in key parts of modern high-rise and long-span engineering and important projects and frequent fires in such buildings in recent years,high-strength concrete is extinguished by fire-fighting measures and artificial water-spraying after high temperature.It is of great significance to study the variation of the performance index with the temperature field after the spray cooling,the damage of the material and the change of the mechanical properties.In this paper,the mechanical properties of water-cooled high-strength concrete materials after high temperature are further studied through experimental research methods.First,a total of 117 high-strength concrete standard prisms of C60,C70,and C80 are produced at 20℃,and fire high temperatures are 200℃,400℃,600℃,800℃,and the constant temperature is 60 min,90 min,120 min,etc.Under the action of water spray cooling method,the test of high-strength concrete specimens was carried out.After the specimens were treated,the apparent characteristics such as color change and crack development were observed,and the change law of burn-in rate after high-temperature water spray cooling was sought.The axial compression test of the water-cooled high-strength concrete specimen was carried out to observe the failure process and failure mode of the specimen.Based on the experimental data of each measured data,the compressive strength,stress-strain curve,peak stress and peak strain,elastic modulus,energy consumption,etc.of high-strength concrete after high temperature were analyzed with temperature and constant temperature duration.The research shows that:the surface color of high-strength concrete which is naturally cooled after high temperature changes,accompanied by cracking phenomenon.With the increase of temperature or the increase of constant temperature duration,the burning loss rate increases gradually,and the compressive strength and elastic modulus of high-strength concrete Significantly reduced,peak stress is reduced,peak strain is increased,and energy consumption is reduced when broken.Finally,through the law obtained by the above test,a preliminary discussion on the evaluation and identification method of high-strength concrete after water spray cooling is proposed.The apparent characteristics and the loss rate of high-strength concrete after fire are used to judge the fire temperature.The length of fire is corresponding to different strength reduction factors,and the residual compressive strength of high-strength concrete after fire can be preliminarily calculated.This has certain reference significance for the evaluation and reinforcement of high-strength concrete structures after fire.