Experimental Study On Permeability Characteristics Of Fiber Reinforced Concrete After Damage

In the water conservancy project,the concrete structure mostly works with cracks,which will affect the service life of the structure.The addition of fiber can improve the mechanical properties of concrete,change the crack shape of concrete,and improve the impermeability of concrete.In order to systematically study the permeability characteristics of concrete with cracks,this paper takes the fiber concrete with cracks as the research object,and adopts the method of indoor test,mainly carries out the basic mechanical property test,disc splitting test,crack morphology observation,damage permeability test.Combined with the hydraulic crack width of concrete,it reveals the non-linear mechanism of concrete permeability.The main research contents are as follows:The results are as follows:(1)Through compressive strength test and flexural strength test,the influence of polypropylene fiber and cellulose fiber with different fiber content(0.6 kg/m3,0.9 kg/m3,1.2 kg/m3 and 1.5 kg/m3)on compressive and flexural properties of concrete was studied.The results show that the addition of fiber can improve the compressive and flexural properties of concrete,the compressive strength and flexural strength increase,and reach the maximum value when the content of fiber is 0.9 kg/m3.(2)In order to explore the influence of fiber content and type,water pressure(0.1 MPa?0.6MPa)and crack shape on the permeability of cracked concrete,the concrete specimens with different crack width range were prefabricated by disc splitting test,and the crack shape was observed.The self-designed damage permeability testing device was used to test the permeability of concrete specimens.The results show that the seepage flow range of fiber reinforced concrete is smaller than that of ordinary concrete;with the increase of effective crack width be,the seepage flow increases gradually;with the increase of fiber content,the seepage flow value tends to decrease;with the increase of water pressure,the seepage flow of the same sample increases substantially.(3)This paper explores the nonlinear characteristics of concrete seepage,studies the relationship between different hydraulic crack width bh and critical Reynolds number,and expounds the evolution mechanism of nonlinear parameters during the change of hydraulic crack width.The results show that the critical Reynolds number decreases with the increase of hydraulic fracture width.The Forchheimer equation can be used to express the nonlinear relationship of water in the process of concrete seepage with cracks,in which the linear coefficient a and the nonlinear coefficient b are negatively correlated with the cube of bh.