Mechanical Properties Of Basalt Fiber Reinforced Reactive Powder Concrete Under Freeze-thaw Cycles

Reactive Powder Concrete(RPC)is a new type of cement-based composite material with the advantages of ultra-high strength and high durability.It has been used in structural design and protection engineering of buildings in complex environments for many times.In the preparation process of RPC,fibers are usually added to improve its performance.As a new type of reinforced,toughened and environmentally friendly inorganic fiber,basalt fiber has a good application prospect.Therefore,in this paper,basalt fiber with high tensile strength,good crack resistance and wear resistance is incorporated into RPC as a modified material,and the mechanical properties of basalt fiber reactive powder concrete(BFRPC)under freeze-thaw cycles are studied.The main research work is as follows:(1)The variation of relative dynamic elastic modulus and mass loss of BFRPC with the number of freeze-thaw cycles was studied,and the effect of fiber content on the frost resistance of reactive powder concrete was analyzed.A freeze-thaw damage evolution model based on relative dynamic elastic modulus is proposed,which accurately describes the relationship between the relative dynamic elastic modulus of BFRPC and the number of freeze-thaw cycles,and analyzes the relationship between the microstructure of BFRPC and its mechanical properties.(2)The effects of basalt fiber content and freeze-thaw cycles on the quasi-static mechanical properties such as compressive strength,flexural strength and splitting tensile strength of BFRPC after freeze-thaw cycles were discussed.The stress-strain relationship of BFRPC under uniaxial compression after freeze-thaw cycles was studied.The influence mechanism of basalt fiber content,freeze-thaw cycles and other factors on the mechanical indexes of RPC was analyzed.The polynomial and rational fraction were used to fit the rising and falling sections of the stress-strain curve of BFRPC after freeze-thaw cycles,and the equation curve of the parameters was determined to be in good agreement with the experimental results.(3)The effects of basalt fiber content,freeze-thaw cycles and strain rate on the dynamic mechanical properties of BFRPC after freeze-thaw cycles,such as dynamic impact compressive strength,dynamic strength growth factor and toughness,were revealed.The dynamic compressive constitutive model of BFRPC was constructed.The mass distribution characteristics of particles with different particle sizes on the impact crushing products were counted by screening equipment.The fractal dimension was used to characterize the crushing degree of the samples.The relationship between peak strength and impact strain rate and fractal dimension was analyzed.The equation was established by regression analysis method,and the fitting effect was ideal.