Experimental Study On Bond Degradation And Improvement Between Non-uniform Corroded Steel Rebar And Concrete

The bond stress between concrete and steel rebar is a necessary condition for the common work,and deterioration of bonding between steel rebar and concrete due to corrosion of steel rebar mainly caused by chloride erosion.In recent years,researchers have studied the bonding properties of corroded steel bar and concrete,but most of these studies use the central pull test on the bonding properties,few studies use the simulating natural non-uniform corrosion method.Based on the accelerated nonuniform corrosion method,this study focus on the bonding properties and the rust expansion and crack mode of corroded steel rebar and concrete,which considers the influence of the placement of steel rebar and the corrosion method on ultimate bond strength between steel rebar and concrete,and the rule of the bond property of corroded structure with the changing corrosion amount of steel rebar under ECC reinforcement was explored.The main research work in this paper are as follows:(1)The corrosion and crack mode of reinforced concrete under non-uniform corrosion were investigated.The crack width of the concrete protective layer at different positions of the steel rebar was measured,and the influence of the orientation of longitudinal ribs in rebar and degree of corrosion on crack width and crack mode were analyzed,and compared with the uniform corrosion.(2)The bonding properties between steel rebar and concrete under non-uniform corrosion was investigated.The bond strength and bond-slip curves of accelerated corroded members under different corrosion rates were measured,and the rule of the bond performance between steel rebar and concrete at different positions and orientation of longitudinal ribs in rebar with the bar corrosion rate was compared.The difference in bonding performance between steel rebar and concrete under non-uniform corrosion and uniform corrosion was compared.The ultimate bond strength model of corroded steel rebar considering the placement of steel rebar and different corrosion methods was established.(3)Based on the non-uniform corrosion of steel rebar,the rule of the bonding properties of eccentric tension member under ECC reinforcement was investigated.The bond strength and bond-slip curves of eccentric tension structures before and after ECC strengthening were measured.The mechanism of bond-slip between steel rebar and concrete before and after ECC strengthening was analyzed.The mechanism of the secondary corrosion after ECC reinforcement to enhance the bond property was explained.Quantitative analysis of the improvement of bonding performance of reinforced concrete structures with different reinforcement thickness.