Experimental Study On Tensile And Compression Properties Of Basalt-coarse Polypropylene Fiber Roller Compacted Concrete

Roller compacted concrete(RCC)has the characteristics of rapid hardening and early strength,and it is widely used in dams,pavements and other projects.,but it is easy to break,low toughness and easy to crack under load,which affects its working performance and service life.Fiber reinforced concrete(FRC)is a new type of composite material with rapid development in recent years.Adding fiber to RCC can also significantly hinder the generation and development of cracks in the matrix,so as to enhance and toughen it.Different fibers can resist cracks step by step and reinforce each other at different levels and scales,so as to improve the performance of concrete better.The improvement effect of coarse polypropylene fiber(CPF)on concrete is similar to that of steel fiber,but its cost is lower and it is not easy to corrode.Basalt fiber(BF)is natural and pollution-free,and has higher elastic modulus than CPF,which can improve the mechanical properties of concrete.Based on this,in this paper,the basalt-coarse polypropylene fiber roller compacted concrete(BCPFRCC)is obtained by mixing BF and CPF,and combining with indoor test,numerical simulation and other means,to study the influence of BF and CPF with different dosages and different mixing ratios on the tensile and compressive properties of RCC.The main research contents and results are as follows:(1)The splitting tensile and cube compressive strength tests of plain RCC and fiber RCC under different curing ages are carried out to study the influence of BF and CPF with different dosage and different mixing ratios on the splitting and compressive strength of RCC under different curing ages.The results show that BF significantly increased the splitting tensile strength of RCC before 7 days of curing age,and CPF has a more significant effect on RCC splitting tensile strength at 7 days of curing age and beyond.The conversion relation between the splitting tensile and compressive strength of the specimens is obtained at different curing age.(2)Through the uniaxial tensile test,the influence of BF and CPF with different dosage and different mixing ratios on the uniaxial tensile properties of RCC is studied.It is found that the brittle failure characteristics of RCC specimens with BF adding separately are similar to those of the plain RCC when subjected to tensile failure,while the addition of CPF makes the tensile failure of RCC present a plastic characteristic,and slows down the slope of the descending section of the axial tensile stress-strain curve,indicating that the post-crack toughness of RCC has been significantly enhanced.(3)Through the uniaxial compression test,the elastic modulus test and the Poisson’s ratio test,the influence of BF and CPF with different dosage and different mixing ratios on the uniaxial compression performance of RCC is studied.It is found that BF and CPF added to enhance the compressive resistance and toughness of RCC.Among them,RCC specimens with a mixture ratio of BF and CPF of 1:2 show the optimal compressive performance and compressive toughness,which reflect the positive effect of fiber hybrid.(4)Refer to the tension-compression damage constitutive model of the code for design of concrete structures(GB 50010-2010),the RCC tensile and compressive stress-strain curve is fitted,and the influence of BF and CPF on the shape parameters of the descending section of the RCC tensile and compressive stress-strain curve is studied,and the damage mechanical properties of RCC are studied by combining with numerical simulation,the results show that BF and CPF decrease the shape parameters of the descending section of the RCC tensile and compressive stress-strain curve;with the increase of inelastic strain and cracking strain of RCC,the compressive damage and tensile damage increase,but the growth rate decreases;the mixing of BF and CPF reduces the cumulative value of compression and tensile damage of RCC.