Study On Bond Slip Behavior Of Steel Bars In Recycled Fiber Reinforced Concrete

The rational use of recycled concrete would be the best way to solve the problem of waste concrete,which not only solves the problem of waste concrete stacking,but also saves resources and prevents it from damaging the environment.However,there are some shortcomings in its properties.It can be improved by adding waste fibers,thus the concept of waste fiber recycled concrete(WFRC)was carried out.Before the WFRC applied in field,apart from its compressive strength,splitting tensile strength or static modulus of elasticity and other basic mechanical properties demand further investigation,the bond performance between reinforcements and WFRC is also a key to structural design.In this research,through semibeam uniaxial pull-out and bond stress distribution tests,the bond performance between reinforcements and WFRC,the bond stress and relative slip distribution in the bond anchorage length were studied.(1)The compressive strength tests of recycled aggregate concrete and WFRC were conducted,and 21 specimens of 7 groups were introduced to investigate the changes in compressive strength of different concrete materials.Conclusion: The compressive strength of recycled concrete was affected by the replacement rate of recycled coarse aggregate(RCA).The increased replacement rate of RCA resulted in the decreased compressive strength.When waste fibers were added into the recycled concrete,as the content of waste fibers increased,the cubic compressive strength increased first and then decreased.The compressive strength was the best when the waste fiber content was 0.12%.Excessive admixture of waste fibers would cause negative effect to compressive strength.(2)A half-beam one-way pull test was conducted,with a total of 26 specimens in 13 groups.By changing the six influencing factors of recycled aggregate replacement rate,waste fiber content,reinforcing bar shape,reinforcing bar diameter,protective layer thickness and anchoring length,the effects of various factors on the bonding properties of half-beam test pieces were studied.The results show that the above six factors have different degrees of influence on the damage form of reinforced steel and concrete,the characteristic values of bond and anchor,limit slip and bond stress-slip curve.(3)Through the bonding stress distribution test,found out that with the loading increased,the stress and strain of each micro-segment was increased;the bonding stress exhibits varying degrees of variation,and the curve had three or four peaks.The appearance of the peaks had nothing to do with the test variables,and the load transfer theory was used to analyze the test results.