Experimental Study On Time-varying Characteristics Of Internal Humidity Of Steel Fiber Reinforced Concrete

As a composite building material,steel fiber concrete is widely used in bridge structures.At present,many scholars at home and abroad have conducted extensive research on the shrinkage resistance of steel fiber concrete,and achieved many results.However,for the above research,there are still many aspects that have not yet achieved good research results,such as: the study of the humidity field in the steel fiber concrete,especially the time-varying characteristics of the humidity inside the steel fiber concrete,the study of the shrinkage deformation mechanism still needs to be deepened.In view of the above problems,based on the theory of concrete humidity field,this paper carried out theoretical and experimental research on the time-varying characteristics of steel fiber concrete humidity field,shrinkage deformation and shrinkage inhibition.The main research work is as follows:(1)Under the condition of dry curing,through the basic mechanical properties test of concrete with different steel fiber content,analyze the influence of three steel fiber content(0%,0.6%,1.2%)on the basic mechanical properties of concrete.The test results show that the added compressive strength of steel fiber is not obvious,and the split tensile strength and elastic modulus of concrete are improved.Among them,the effect of improving the split tensile strength is the most obvious,and the steel fiber content is The splitting tensile strength of 0.6% and 1.2% concrete is increased by 15.7% and 44.6%respectively compared with ordinary concrete.(2)Through the shrinkage test of steel fiber concrete,it was found that the internal humidity of the specimen dropped rapidly in the early stage,and the rate of decline gradually slowed down in the later stage.From the surface of the concrete specimen to the center,the degree of decrease in the internal humidity of the concrete gradually decreases.At the same age,the relative humidity of the samples with 0% steel fiber content at 3cm and 5cm from the surface decreased from 97.48%,96.91% to 79.37%,84.17%,and the sample content of 0.6% from 96.51%,96.36% decreased to 80.41%,85.53%,and the amount of 1.2% of the test pieces decreased from 95%,96.28% to82.38%,85.43%.The shrinkage strain of the test piece with the steel fiber content of 0%is 127.3% and 153.6% of the same age content of the sample with 0.6% and 1.2%.(3)The program of random distribution of steel fibers was compiled using MATLAB,and the spatial finite element simulation of concrete samples with different steel fiber content was realized.The analysis results can well reflect the development and change of measured data.(4)Relying on the Changshou Bridge reinforcement project,the internal humidity and shrinkage strain of the reinforced steel fiber reinforced concrete were measured,and the development law of humidity and shrinkage strain of the reinforced structure was simulated by finite element software.The monitoring and analysis results show that: steel fiber concrete can effectively suppress shrinkage,thereby reducing uneven deformation between concrete layers,improving the crack resistance of concrete,and effectively avoiding the cracking problem of reinforced structures.