Study on the bond behavior of steel bars embedded in concrete under the coupling of sustained loads and chloride ion erosion

Abstract

The 27 reinforced concrete beam test specimens of 550 mm × 150 mm × 100 mm with initial cracks were used to investigate the bond properties of steel bars embedded in concrete under the action of three different levels of sustained loads (25%, 45% and 65% of ultimate load) alone, chloride attack (NaCl solution with a concentration of 5%) alone and coupling of sustained loads and chloride attack for 180 d. Based on the test results, the influence of three working conditions on bond behavior between steel bars and concrete has been compared and analyzed. Subjected to the same load level, the bond stress between steel bars and concrete under chloride attack was higher than that without chloride attack, the bond strength of the specimen subjected to the coupled effect of sustained load and chloride ion attack was higher than that under the single factor. As the load level increased, the bond strength of steel bars embedded in concrete gradually decreased whether there was chloride ion attack or not. When the corrosion ratio of the longitudinal bars was small (corrosion ratio ≤ 0.14 without chloride ion corrosion and corrosion ratio ≤ 0.28 with chloride ion corrosion), the bond strength between steel and concrete gradually increased with the increase of the load level; with the further improvement of the corrosion ratio of steel bars, the bond strength showed a decreasing trend. The free end slip of specimens is smaller than the load end. Based on the test results, the reinforced concrete bond-slip curves and its constitutive relationships under different conditions have been proposed.