Experimental Study On Bond-slip Performance Of Steel Bar And Steel Fiber Recycled Concrete

Recycled concrete is an important means to realize the recycling of construction wastes,which conforms to the strategy of sustainable development.However,the performance of recycled concrete is insufficient.By adding steel fibers,the physical and mechanical properties of recycled concrete can be improved,and then the bearing capacity and deformation capacity of recycled concrete can be optimized.In order to further promote the application of recycled concrete in the civil construction industry,the basic mechanical properties of recycled concrete,bond-slip behavior of steel bar and steel fiber recycled concrete were tested,and the bond-slip constitutive relationship model was proposed.The main research contents are as follows:(1)Study on the basic mechanical properties of steel fiber recycled concrete.Based on 25 groups of mechanical properties tests of recycled concrete,the variation of compressive strength,tensile strength and flexural strength of recycled concrete under different replacement rates of recycled aggregate and different volume fraction of steel fiber was studied.The results show that with the increase of replacement rate of recycled aggregate,the basic mechanical properties of concrete show a downward trend;within a certain range,with the increase of steel fiber content,the basic mechanical properties of concrete show an overall upward trend;(2)Study on bond-slip behavior between steel bar and steel fiber recycled concrete.The influence of replacement ratio of recycled aggregate,volume fraction of steel fiber,diameter of steel bar and anchorage length on bond slip behavior of steel bar and steel fiber recycled concrete was studied by central pull-out test of 33 groups of steel fiber recycled concrete blocks.The results show that the higher the replacement ratio of recycled aggregate,the lower the bond strength between steel bar and steel fiber recycled concrete;the higher the content of steel fiber in the range of 0-1.2%,the greater the bond strength of the specimens;the higher the content of steel fiber in the range of 0-1.6%,the greater the slip value of the specimens under peak load;the incorporation of steel fiber improves the failure mode of the recycled concrete drawing specimens,and the steel fiber improves the bond strength of the specimens.When the fiber content is 1.2% and 1.6%,the pull-out failure occurs mainly;when the diameter of steel bar increases,the pull-out load increases,but the ultimate bond strength decreases slightly;when the anchorage length increases,the bond strength first increases and then decreases,and when the relative anchorage length is 5 days,the bond strength is the highest;the bond-slip curve of ordinary concrete and recycled concrete specimens only has an ascending section.The bond-slip curves of steel fiber recycled concrete specimens are relatively complete,the crack distribution is more,the width is smaller,and the integrity of the specimens is better;(3)The bond-slip constitutive model of steel bar and steel fiber recycled concrete is modified.Through systematic experimental research and theoretical analysis,the bond-slip constitutive relationship between steel bar and steel fiber recycled concrete is revised.Based on the non-linear regression,the influence of replacement ratio of recycled aggregate and steel fiber content on bond performance is analyzed,and compared with the experimental results.The results show that the experimental curve is in good agreement with the fitting curve,which can provide theoretical support for engineering application.