Experimental Study On The Effect Of Basalt Fiber On The Mechanical Properties Of Recycled Concrete

Basalt fiber aggregate concerete(BFRAC)is a green and environmentally friendly composite material,which mixes the random distribution of short basalt fiber into the recycled concrete.The research shows that the mechanical properties of recycled concrete are poor,and the existence of basalt fiber restricts the development of cracks to some extent,so that the recycled concrete which was originally brittle failure presents a certain ductility and toughness,and has excellent tensile and fatigue resistance characteristics.Therefore,It is one of the effective ways to improve the mechanical properties of recycled concrete.In this paper,the regenerated concrete was prepared by using the regenerated coarse aggregate with the replacement rate of 20%.150 standard cube specimens of150mm×150mm×150mm were made,of which 60 were used for compressive and tensile tests,and 90 were used for uniaxial compressive fatigue tests at three stress levels.30 trabecular specimens of 150mm×150mm×550mm were made for the four-point bending strength test.In this paper,the basic mechanical properties(compressive strength,splitting tensile strength,four-point bending tensile strength),uniaxial compressive fatigue failure characteristics,fatigue life and damage evolution of recycled concrete with lengths of 6mm,9mm and 12 mm with volume content of 0.1%,0.2% and 0.3% are studied.The main research contents and conclusions are as follows:(1)the compressive strength,splitting tensile strength and four-point bending tensile strength of the specimens were tested,and the effects of basalt fibers of different lengths and different contents on the basic mechanical properties of the recycled concrete were compared,and the failure patterns of the specimens were observed.The results show that the addition of basalt fiber can affect the performance of recycled concrete.The compressive strength and tensile strength of the basalt fibers of different lengths to the regenerated concrete increased first and then decreased with the volume content.The most significant effect was the increase in the flexural strength.(2)according to Weibull distribution theory,the fatigue life test results of basalt fiber regenerated concrete under uniaxial compressive fatigue were tested.The results show that the fatigue life of the test can obey the weibull two parameter distribution well.According to the experimental results,the maximum fatigue strain diagram is drawn,and it is found that the evolution law of the maximum compressive fatigue strain of basalt fiber regenerated concrete is obvious in three stages.(3)the uniaxial compressive fatigue performance of basalt fiber recycled concrete was experimentally studied,and the fatigue life under different stress levels(S=0.85,0.8,0.75)was obtained.The results show that the single logarithmic fatigue life equation and the double logarithmic fatigue life equation show a linear relationship under different survival rate P and different stress levels,among which the double logarithmic fatigue life equation has the best fitting effect.The fatigue limit strength of each specimen was estimated and analyzed according to the double logarithmic fatigue equation.