Study On Mechanical Properties Of PVA-steel Fiber Reinforced Cemrnt-based Materials

Fiber reinforced cement-based material is a kind of composite material with short cut fiber mixed into cement-based material.ECC(Engineered Cementitious Composite)engineering composite cement-based materials are the primary representative,it has the strain hardening characteristics that ordinary cement-based materials do not have.In the case of bending stress,it shows the nature of multiple cracks.It is a new cement-based material developed to overcome the problems of brittleness,cracking,poor tensile and bending properties of ordinary cement-based materials.In this paper,on the basis of ECC,PVA fiber and steel fiber were mixed in a certain proportion to strengthen and toughen cement-based materials.The purpose of matching high strength and high bending toughness of composite cement-based materials is achieved.In this paper,the bending and compression properties of PVA fiber and steel fiber reinforced cement-based materials are studied.A total of 16 groups of test pieces were designed.The compression test of cube specimen and the bending test of thin plate under two-point loading at the third point were carried out.Then,the nonlinear regression analysis of the compression and bending test results is carried out.The prediction models of compressive strength,ultimate flexural strength and ultimate mid span deflection are established.Then the constitutive model of compressive stress-strain curve is established for the composite cement-based materials.It is found in the compressive test of the cube specimen of PVA steel fiber reinforced cement-based material that,When the volume content of steel fiber in cement-based materials is more than 0.6%.The compressive strength of steel fiber increased by 24% when the volume fraction of steel fiber was 0.8%.Steel fiber can greatly improve the compressive strength of cement-based materials.The compressive strength of PVA fiber increased by 13% when the volume content of PVA fiber was 1.6%.The compressive strength of the cube is also improved by adding PVA fiber.When mixed with two kinds of fibers,the maximum compressive strength is 45% higher than that of plain cement-based materials.Compared with the increase of steel fiber,the two have a positive synergistic effect.Non linear regression analysis is carried out on the compressive strength value obtained from the test.The prediction model of the content of PVA fiber and steel fiber to the compressive strength value is established.The prediction model of the content of PVA fiber and steel fiber to the compressive strength value is established.According to the stress-strain curve of PVA steel fiber reinforced cement-based material in cube compression test,the constitutive model of the stress-strain curve is established.It provides a reference for structural design and stress calculation in practical engineering application of PVA steel fiber composite reinforced cement-based materials.Three point loading test was carried out on PVA steel fiber reinforced cement-based material sheet.The plain cement-based material without fiber has poor bending resistance,almost no toughness,and is brittle.The plate is broken directly during loading.When PVA fiber is mixed with steel fiber,the initial crack deflection increases and the deformation capacity is better.The maximum deformation rate is 6%,and the ultimate bending strength also increases.The nonlinear regression analysis of the ultimate flexural strength and the ultimate midspan deflection is carried out to establish the prediction model.