Experimental Research On Mechanical Properties Of Hybrid Fiber Reinforced Concrete After High Temperature

Concrete has become one of the most widely used civil engineering materials in the world.It has some shortcomings such as poor tensile strength,high brittleness and easy cracking,which limits its application.Especially in recent years,frequent fire accidents have seriously threatened the safety of public property and people's lives.Therefore,considering the fire protection performance of materials has become one of the important subjects of structural design.Nowadays,people are constantly exploring new concrete materials to make them develop in the direction of high efficiency,high performance and green.Previous studies have shown that adding fibers into concrete can improve the mechanical properties of concrete and improve its high temperature resistance.In this paper,the effects of temperature,fiber content and fiber length on the mechanical properties of concrete are considered.The effects of single and mixed fibers on the compressive,tensile and flexural strength of concrete specimens at room and high temperatures are studied.The main research contents are as follows:(1)The mechanical properties of fiber reinforced concrete with basalt fibers and cellulose fibers are compared with those of ordinary concrete.The results show that the addition of fibers into concrete can effectively remedy the shortcomings of high brittleness and low tensile strength of concrete.And basalt fiber is better than cellulose fiber in improving compressive strength,while cellulose fiber is the most effective in improving splitting tensile strength.(2)Consider the influence of different fiber content and different fiber length on the mechanical properties of concrete.The results show that with the increase of fiber length and fiber content,the cubic compressive strength and flexural strength of concrete increase first and then decrease.That is to say,only when the fiber length and fiber content are appropriate,the fiber reinforced concrete can play the role of strengthening concrete.(3)The effects of fiber length,fiber content and temperature on the mechanical properties of hybrid fiber reinforced concrete are studied by test.The results show that the compressive strength of hybrid fiber reinforced concrete increases first and then decreases with the increase of temperature,while the splitting tensile strength and flexural strength decrease after high temperature,and the tensile and flexural strength decrease gradually with the increase of temperature.(4)The mechanical properties of ordinary concrete and hybrid fiber(basalt fiber,cellulose fiber)concrete after high temperature are compared.The results show that when the length and content of fibers are constant,hybrid fiber concrete shows stronger heat resistance.The bearing capacity of ordinary concrete decreases rapidly after high temperature,while that of hybrid fiber concrete decreases slowly.It shows that hybrid fiber concrete can play a better role after high temperature.