Study On The Influence Of Emery And Steel Fiber On The Performance Of Recycled Concrete After Chorine Salt Soaking Processing

Recycled concrete as a kind of economy,environmental protection material to solve the problem of waste concrete,driving the development of the green concrete industry,recycled concrete due to the addition of recycled aggregate concrete performance degradation,and the addition of steel fiber,silicon carbide can improve the strength of the recycled concrete,make up for a lack of some recycled aggregates;The durability of concrete is also a common concern in the engineering field.One of the reasons for the damage of concrete structure is the damage caused by chloride erosion.The influence of chloride environment on the mechanical properties of concrete is also complex.Therefore,it is of great practical significance to study the mechanical properties of steel fiber recycled concrete and emery sand recycled concrete under the condition of chloride immersion.Based on ordinary C30 concrete(C),recycled coarse aggregate replaces 20%natural coarse aggregate to make recycled concrete(RC).On the basis of recycled concrete,steel fiber recycled concrete(SFRC)was made by adding 1.0% steel fiber.Emery regenerated concrete(SiCRC)with quality of 10% fine sand instead of emery.In this paper,the effects of immersion time of 0d,30 d,60d and 90 d on the static mechanical properties and bending fatigue properties of steel fiber recycled concrete and emery sand recycled concrete were studied under the condition of 5% NaCl solution immersion.Based on the above research,the following main conclusions are drawn:(1)The color of the specimens soaked in chlorine deepened,and the surface of SFRC showed signs of corrosion,while other types of concrete showed no obvious difference.With the increase of chlorine soaking time,the cube compressive strength,cube splitting tensile strength and four-point bending strength of SiCRC,RC and C increased to a small extent,while SFRC was on the contrary.When the soaking age reached 90 d,the compressive strength of the cube,the splitting tensile strength of the cube and the bending strength of the four-point bending increased by 21.0%,16.7% and4.2% respectively,and the SFRC decreased by 12.5%,25% and 16.3% respectively.The results showed that chlorine soaking was beneficial to SiCRC,RC and C,but not to SFRC.(2)The macroscopic performance of all types of concrete is roughly similar.After cyclic loading,they all break into two pieces.In terms of macroscopic numerical performance,under the same stress level and at the same soaking age,the fatigue life of RC is obviously lower than that of c.with the increase of soaking age,the fatigue life of SiCRC,RC and C increases steadily,while the fatigue life of SFRC decreases gradually.Each type of concrete fatigue life-strain curve is roughly same,is divided into three stages,the first stage for the elastic stage,the strain fatigue life with the rapid increase,the second stage,crack and stable development of smooth curve to develop relatively slowly,the third stage,the cracks with the increase of load frequency rapid growth,the fatigue life of stress-strain curve rapidly rising,until the destruction.(3)Based on different age of chlorine salt immersion C,under the condition of the RC and SFRC and SiCRC bending fatigue life test using weibull distribution theory,the test results showed that C,the RC and SFRC,SiCRC can better obey the two parameter weibull distribution,linear fitting correlation is higher,is obtained by computing the proportion of different specimens under different stress level,the fatigue life of differentsurvival conditions;According to the fitting of fatigue life and stress levels of C,RC,SFRC and SiCRC at different soaking ages,the bi-logarithmic fatigue equations of each mix sample were deduced,and the correlation coefficient of the bi-logarithmic fatigue equations was relatively high.Set N=2000000,the fatigue strength of each mix sample was calculated.It was found that the fatigue strength of C,RC and SiCRC was increased by chlorine salt immersion.Compared with 0d,the fatigue strength of SiCRC was increased by 0.15%,0.30% and 0.46% respectively at 30 d,60d and 90 d,while the fatigue strength of SFRC decreased with age,by 0.34%,0.74% and 1.08% respectively.The influence of chlorine on the fatigue strength of steel fiber recycled concrete is obvious.