Experimental Study On Durability Of Basalt Fiber Recycled Aggregate Concrete

Recycled aggregate concrete(RAC)is the recycling of waste concrete,which can not only solve the problem of stacking construction waste,but also conform to the green and sustainable development advocated by the country.However,old mortar is attached to the surface of recycled coarse aggregate(RCA),and a large number of cracks are easily generated inside the aggregate during the preparation process,resulting in defects such as large crushing index and high water absorption ratio.These defects seriously affect the durability of RAC.In order to improve the durability of RAC,basalt fiber(BF)is added by the method of admixture,and the impact of the replacement ratio of RCA and the content of BF on the anti-carbonization,anti-chloride ion penetration,and anti-freezing properties of basalt fiber reinforced recycled concrete(BFRRC)is analyzed from the macro-indices and micro-structure.The main research contents and conclusions are as follows:(1)Carry out rapid carbonization,chloride ion penetration and rapid freeze-thaw cycle tests on BFRRC,measure carbonization depth,unsteady state chloride ion migration coefficient,appearance damage,mass loss,relative dynamic elastic modulus(RDEM)loss and other indicators,and analyze the influence of BF content and RCA replacement ratio on durability.(2)The test results show that as the replacement ratio of RCA increases,the carbonation resistance and frost resistance of RAC increase first and then decrease.The RCA replacement ratio is 50%shows better carbonation and frost resistance than natural aggregate concrete(NAC)performance;as the replacement ratio increases,the chloride ion resistance of RAC decreases first and then increases.Under 100%replacement ratio,the chloride ion resistance of RAC is closer to that of NAC.(3)Incorporating BF into RAC can improve its durability,but the content of BF is not as high as possible,and there is an optimal content.For the anti-carbonization performance of RAC,the optimum amount of BF is 2kg/m~3;the addition of 4kg/m~3 of BF has a more obvious effect on the improvement of the anti-chloride ion of RAC.Compared with the mass loss,the RDEM can better characterize the frost resistance of BFRRC.Adding 4kg/m~3 of BF can most effectively reduce the RDEM loss of RAC.(4)Using scanning electron microscope to observe the microstructure of BFRRC,combining damage theory and composite material theory to analyze the durability damage mechanism of BFRRC and fiber reinforcement.(5)Based on the test data and using the regression analysis method,a carbonization,chloride ion,and freeze-thaw damage model was established.The established model can simply and accurately reflect the durability damage law of BFRRC and provide a reference for engineering practice.