Experimental Study On Properties Of Basalt-Polypropylene Fibre Reinforced High Performance Concrete

Concrete will inevitably suffer from load damage during the whole life cycle of a building,which reduces the mechanical properties and durability of the structure.Concrete structures are at risk of failure collapse when the damage to the structure reaches a critical value.Based on the above background,this paper plans to mix Basalt fiber(BF)and Polypropylene fiber(PF)into high performance concrete(HPC).The durability and mechanical properties of basalt polypropylene fiber reinforced high performance concrete(BPHPC)were investigated through basic mechanical tests and freeze-thaw cycle tests,and the damage mechanism of BPHPC was further analyzed from a microscopic perspective.In addition,the damage monitoring of the freeze-thaw process and compressive process of BPHPC is performed based on the piezoelectric effect.The main studies and findings are as follows:(1)BF and PF have enhanced effects on the cubic compressive strength,splitting tensile strength,and flexural strength of HPC before and after freeze-thawing.The addition of BF and PF in different ratios to the HPC matrix results in different enhancement effects.BF has a high modulus of elasticity to effectively enhance the strength of HPC,and PF can give full play to the bridging effect to enhance the toughness and ductility of HPC.Each of the two fibers plays an advantage to improve comprehensively the mechanical properties of concrete.(2)From the rapid freeze-thaw test,it was found that the fibers can bond well with the cement paste on the surface of the specimen,thus restraining the cement paste from falling off the surface,which can reduce the mass loss rate of HPC after freeze-thaw.Both BF and PF can retard the reduction of relative dynamic modulus of elasticity,the reinforcing effect of BF is stronger than PF,and the reinforcing effect of multiple fiber combinations is stronger than that of single fibers.(3)Monitoring of BPHPC damage based on piezoelectric effects.The damage index(DI)based on wavelet packet analysis method was obtained by analyzing the piezoelectric stress wave signals of concrete specimens with single and hybrid fiber,and the correlation function relationship of fiber content-load-DI and fiber contentnumber of freeze-thaw cycles-DI were fitted.It is proved that damage monitoring of BPHPC based on piezoelectric ceramics is a feasible method by the damage state of the appearance,the regularity of strength change with the time domain signal diagram,the number of freezing and thawing cycles-DI curve,and the load-DI curve.