Experimental Study On The Mechanical Properties And Durability Of Hybrid Fiber Self-compacting Concrete

A large number of engineering practices show that self-compacting Concrete(SCC)can not only reflect good fluidity,but also need not fully vibrate in the construction process,so it has been greatly promoted and applied.It can be seen from the current academic field that there are many related research theories on single-fiber self-compacting concrete,and most of them focus on working performance,mechanical properties,durability and microscopic analysis,while there are few researches on the performance of hybrid fiber self-compacting concrete.This paper takes "Experimental study on the mechanical properties and durability of hybrid fiber self-compacting concrete" as the title,and uses different fiber types and different fiber volume content as basic variables to study the influence of hybrid fiber on self-compacting concrete.The working performance test,basic mechanical properties test,compression and tensile strength test after sulfate erosion,sulfate ion concentration measurement test,X-ray diffraction test and scanning electron microscope test of self-compacting concrete were carried out.The main contents of the test are as follows:(1)Basalt fiber(0.05%,0.10%,0.20%)and polyacrylonitrile fiber(0.06%,0.09%,0.12%)were mixed into self-compacting concrete to conduct performance tests.It mainly includes slump extension test,J ring slump extension test,extension time(T500)test,J ring height difference test and V-funnel test,the analysis shows that the increase of fiber content will significantly reduce the flow and clearance of self-compact concrete.(2)The compressive strength and splitting tensile strength test results of self-compacting concrete with fiber at different ages(7d and 28d)show that basalt fiber and polyacrylonitrile fiber have better improvement effect on the tensile strength of concrete,but the improvement effect on compressive strength is not obvious.The tensile strength of 7d and 28d hybrid fiber self-compacting concrete is 87.55%and 75.45%higher than that of plain self-compacting concrete,respectively.(3)Through working performance test and basic mechanical properties test,four groups of self-compacting concrete with the appropriate dosage in the test were determined,and the sulfate resistance test of fiber self-compacting concrete was carried out by natural soaking method.The results show that the mechanical properties of plain self-compacting concrete are most affected by sulfate erosion.In the initial stage of soaking,the compressive and tensile strength of the four groups of self-compacting concrete increased slightly.Ettringite generated inside the concrete filled the pores and increased the strength of the concrete slightly.Then,the sulfate ion concentration of four groups of optimal mixtures of concrete with different erosion depths and different erosion ages was measured by gravimetric method.The experimental results show that the sulfate ion concentration of fiber self-compacting concrete is lower than that of plain self-compacting concrete.At the same time,the changes of cement-aggregate bond surface,fiber-matrix bond surface,hydration products and internal phase microscopic morphology of self-compacting concrete before and after sulfate erosion were analyzed by X-ray diffraction test scanning electron microscope.In this paper,it is verified that adding basalt fiber and polyacrylonitrile fiber into concrete has a positive effect on the improvement of concrete strength,and can improve the sulfate resistance of concrete,which provides a theoretical basis for the application of fiber in engineering practice.Figure 28 table 15 references 78...