| Since the beginning of the new century,high-rise buildings have been increasing.Among them,pumped concrete is the most widely used.However,pumped concrete has serious early cracking problems and poor volume stability.Based on the consideration of the above problems,a new post-aggregate concrete technology with “coarse aggregate interlocking” as the core concept has attracted attention and been developed.This paper designed the C30 benchmark concrete that meets the requirements of workability,and then simulated the coarse aggregate post-mixing process in the project,and obtained the coarse aggregate post-mixing rate of 0%,10%,15%,20%,25% and 30% postmixed aggregate concrete.Then,the effects of different coarse aggregate post-mixing ratios on the compressive strength and elastic modulus of concrete specimens were experimentally studied.With reference to the standard,the impermeability performance of the post-aggregate concrete was tested and the results were compared and analyzed.Subsequently,the residual compressive strength and flexural strength of concrete with different coarse aggregate postadmixture ratios at different high temperatures(200℃,400℃,600℃ and 800℃)were tested through experiments.Then,the mass loss,ultrasonic velocity and relative dynamic elastic modulus of concrete after high temperature were tested.At the same time,the feasibility of using ultrasonic velocity and relative dynamic elastic modulus to detect the residual compressive strength and residual flexural strength of post-aggregate concrete was studied.From the test results,it can be seen that increasing the post-mixing rate of coarse aggregate can significantly increase the elastic modulus and cubic compressive strength of the post-mixed coarse-aggregate concrete,with the subsequent increase in the rate.At the same time,the elastic modulus and compressive strength show a changeable rule of first increasing and then decreasing.At the same time,as the post-admixture rate of coarse aggregate increases,the impermeability of concrete increases first and then decreases.The post-admixture rate of coarse aggregate with the best impermeability is 15%.After treatment at the same high temperature,the residual compressive strength and flexural strength of the concrete increased first and then decreased with the increase of the coarse aggregate post-admixture rate.The best hightemperature performance of the specimen was 20% after the coarse aggregate admixture rate.At the same time,the research results in this paper show that the ultrasonic velocity and relative dynamic elastic modulus can be used to detect the compressive strength and flexural strength of aggregate concrete after high temperature. |
