Bond properties between bimetallic steel bar and early-age marine concrete

To investigate the engineering applicability of bimetallic steel bars and sea water sea sand concrete, concentric pull-out tests were carried out on sea water sea sand concrete and sea water sea sand concrete containing polyoxymethylene (POM) fibers. Considering different concrete ages and ratios of concrete cover c to bar diameter d(c/d), the influences of the two variables on bond performance were studied to quantify the bond-slip relationship. Test results show that bimetallic steel bar was suitable for the reinforcement of sea water sea sand concrete because of its good performance. The peak bond stress τu between the early-age concrete and the steel bar was significantly affected by the age, and the sea water sea sand concrete with POM fibers added had better ductility and bonding properties. The influence of concrete age on the slip value su corresponding to the peak bond stress and the shape parameter α of the ascending section was generally manifested as the larger the age was, the smaller the slip value su was, and the smaller the parameter α was. With increasing concrete age, the shape parameter k of the descending section was increased. Based on the test results, a bond-slip model of bimetallic steel bar and sea water sea sand concrete was proposed considering the effect of concrete age, and the model was in good agreement with the test results. The research indicates that bimetallic steel bar and pure sea water sea sand concrete can be used in engineering applications, and the concrete improved by adding POM fibers has better performance. © 2022 Harbin Institute of Technology. All rights reserved.