Study On Bonding And Corrosion Behavior Of Rebar And Calcined Nano Attapulgite Reclaimed Concrete

Recycled concrete is the most important way to solve the waste resource at present,and also belongs to the sustainable development strategy.However,due to the defects in the performance of recycled concrete itself,it must be improved if it is to be used in the actual construction.By adding 500℃ calcination to produce nano attachable rod concrete(CNAT),the performance of recycled aggregate can be improved.Optimize recycled concrete defects.On this basis,this project intends to use laboratory experiments,and systematically study the mechanical properties of CNAT recycled concrete,the change law of adhesion force and slip between steel bar and nano attapulgite under different regenerated aggregate replacement rate and CNAT content,and the effect of CNAT on steel bar corrosion in recycled concrete.According to the test results,the bond slip constitutive model between the rebar and CNAT regenerated concrete is modified.The main research contents are as follows:(1)Study on Mechanical Properties of Recycled Aggregate Concrete with CNAT.With recycled aggregate replacement rate(0%,50%,100%)and CNAT content(0%,3%,6%,9%)as variables,the influence of these factors on the compressive strength,splitting tensile strength and flexural strength of recycled concrete was investigated.The experimental results show that with the increase of CNAT content,the mechanical properties of recycled concrete first increase and then decrease,and the mechanical properties are best when the CNAT content is 6%;the higher the replacement rate of recycled aggregate,the worse the mechanical properties of recycled concrete.(2)Study on bond slip property of steel bar and CNAT recycled concrete.The bond strength and bond stress-slip relationship between rebar and CNAT regenerated concrete were studied by central pull out test with CNAT content and regenerated aggregate substitution rate as variables.The results show that: when the CNAT content and the replacement rate of recycled coarse aggregate are low,the bond strength of reinforcement can be improved,but when the CNAT content is too high or the replacement rate of recycled coarse aggregate reaches a certain degree,the bond strength of reinforcement will be reduced.The bond strength is optimal when the replacement rate of recycled coarse aggregate is 50% and the CNAT content is 6%.The constitutive relation equation of bond slip of reclaimed concrete proposed by Haraji was used to fit the experimental data,and the fitting curve was compared with the experimental curve,and it was found that the fitting effect was better.(3)Study on corrosion behavior of CNAT recycled concrete to steel bar.Electrochemical corrosion test was used to study the influence of CNAT content and regenerated coarse aggregate replacement rate on the corrosion properties of steel bars under different corrosion time,and the changes of internal microstructure were analyzed by SEM and pore volume and aperture.The results show that CNAT can fill the pores of recycled concrete and make concrete more dense.The incorporation of CNAT can effectively prevent chloride ions from entering the interior of recycled concrete and reduce the corrosion of reinforcement.The best effect is achieved when the content of CNAT is 6%,and the corrosion of 24 h and 48 h is reduced by 21% and33% respectively compared with ordinary concrete.