Study on the bond performance of steel bars in early-age concrete considering the effect of circumferentially lateral pressures

Abstract

The interface performance between steel bars and concrete is the fundamental necessary parameter in the bearing capacity evaluation of reinforced concrete structures, especially for those during construction in some developing areas where the plain bars were still adopted as the reinforcing materials. The age-correlation of the chemical adhesive force and frictional resistance at the plain bars-concrete interface needs to be investigated in detail but has not yet been deeply understood. Therefore, a systematic study including both the experimental and theoretical investigations on the bond behavior of plain steel bars in early-age concrete with lateral pressures was performed on the pullout specimens, with consideration of the influencing parameters including the bar diameters, the concrete strengths, and the ages. On the base of the experimental results, the calculation models for predicting the bond parameters of plain bars in early-age concrete under lateral pressures were derived and verified with the test results, and then a suited local bond-slip model was presented. Finally, a comparison of enhanced early-age bond strength caused by lateral pressure obtained from the experimental and the theoretical approaches was provided with reasonable agreement.