Evaluation of residual bond behaviour between rebar and recycled aggregate concrete after high-temperature exposure followed by water spray cooling

Abstract

This paper presents an evaluation of the residual bond behaviour between rebar and recycled aggregate concrete (RAC) using granite natural coarse aggregates and different recycled coarse aggregate (RCA) replacement levels (δ = 0%, 30%, 50%, and 100%) for both pull-out and cubic specimens. After high-temperature exposure (T = 200, 400, and 600 ℃) followed by water spray cooling, the results revealed a consistent decline in bond strength and compression strength with increasing temperature. Compared to ambient conditions, bond strength and compression strength decreased by 65.2% ∼ 77.8% and 53.2% ∼ 58.4%, respectively, after exposure to 600 ℃. The reduction rate of residual bond strength changed significantly at about 400 ℃. There was a linear relationship between RAC compression strength and rebar–RAC bond strength after high temperature exposure followed by water spray cooling. With increasing RCA replacement levels, the relative bond strength gradually improved at the same temperature. Based on the regression analysis, empirical formula for the rebar–RAC bond strength and bond–slip relationship models were proposed, all taking into account RCA replacement levels and temperature.