Bond behavior between deformed steel bars and recycled aggregate concrete after freeze-thaw cycles

Abstract

In cold regions, freeze-thaw damage can deteriorate the structural performance of reinforced concrete structures. This paper investigated the bond behavior between recycled aggregate concrete (RAC) and deformed steel bars after freeze-thaw cycles (FTCs). Sixty-three specimens for pull-out tests were prepared with three different recycled coarse aggregate replacement ratios (0%, 30% and 50%) and seven different FTCs (0, 50, 100, 150, 200, 250 and 300). Additionally, nine made-to-measure pull-out specimens with built-in strain gauges were tested to tentatively study the bond stress distribution along the interface between the steel bars and the RAC after the FTCs. The results show that as the FTCs increased, the bond strength decreased and became increasingly significant as the RCA replacement ratios increased, while the bond slip was relatively stable as the FTCs increased and exhibited a similar increasing trend for all the mixtures at the higher number of FTCs. The bond stress focused on local areas and formed local stress concentrations when the pull-out force was close to the peak value. Finally, a two-segment bond stress-slip model to describe the bond behavior between RAC with RCA replacement ratios less than 50% and deformed steel bars after FTCs was proposed, showing a good correlation with the test results.