Study On Uniaxial Compression Constitutive Relation Of Acicular Wollastonite Hybrid Fiber Reinforced Concrete

Fiber concrete has been widely used in domestic and foreign engineering because of good economic and physical and mechanical properties.However,single fiber reinfoRced concrete usually only has superior performance in some aspects.which greatly limits the promotion and application in practice.For hybrid fiber concrete,the advantages of binary or multi-component hybrid fibers can be exerted at the same time,and the toughness.strength and durability of the concrete matrix can be effectively improved,and more and more attention is paid to the engineering and scientific reseaRch ciRcles.At present.the theoretical research on single-fiber-reinfoRced concrete has achieved a lot of research results,and the theoretical system has been gradually established.However.there are few reseaRches on hybrid fiber concrete,and most of them are research on steel fiber hybrids.and other types of fiber hybrid research.Rarely,there is a serious lack of relevant norms and regulations,and it is urgent to establish a mature theoretical system.There are still many problems to be studied about the constitutive relationship of hybrid fiber concrete.In this paper,the stress-strain curves of C40 and LC20 acicular wollastonite-polypropylene hybrid fiber reinforced concrete are obtained by adding test methods for increasing the stiffness of the test machine.The main research contents and conclusions are as follows:(1)Based on the test results,for the C40 hybrid fiber concrete,as the volume fraction of the acicular wollastonite fiber increases,the curve ascending section is closer to the peak point than the initial crack point of the ordinary concrete and the single fiber-reinforced concrete,and The curve near the peak point is more full and the curve falling down is more gradual.For LC20 lightweight aggregate hybrid fiber concrete,the stress-strain curve is similar to that of ordinary lightweight aggregate concrete.As the fiber content increases.the curve near the peak point is more full,but the elastic section of the curve ascending section is longer.For the descending section of the curve,the ordinary lightweight aggregate concrete approximates an oblique straight line before the maximum point of curvature,and as the volume fraction of the fiber increases,the area enclosed by the descending section and the x-axis increases remarkably.This shows that the hybrid fiber concrete has a more pronounced effect on the matrix than the single fiber-reinforced concrete.(2)The two fibers have similar peak strength and peak strain enhancement effects on C40 and LC20 hybrid fiber concrete.The factors are arranged in order of order:acicular wollastonite fiber and polypropylene fiber,acicular wollastonite fiber,polypropylene.fiber.(3)The constitutive relationship of C40 and LC20 hybrid fiber concrete is proposed,and the concrete coefficients of the two types are different.According to the characteristics of hybrid fiber concrete,the constitutive relation of C40 and LC20 hybrid fiber concrete is represented by the analysis of the existing concrete constitutive relation model,using the ascending section as a polynomial and the descending section as a rational fraction.