Bond behaviour of deformed steel bars embedded in recycled aggregate concrete

The results of sixty pullout tests carried out using 12 mm, 16 mm, 20 mm and 25 mm diameter deformed steel bars concentrically embedded in recycled aggregate concrete designed using equivalent mix proportions with coarse recycled concrete aggregate (RCA) replacement levels of 0%, 25%, 50%, 75% and 100% are reported towards investigation of bond behaviour of RCA concrete. It is postulated that due to internal curing action of the RCA particles, the relative bond strengths, obtained by normalising the measured bond stress with the respective compressive strength of concrete, across all the RCA replacement levels were higher for the RCA concrete compared to the NCA concrete. Further, the relative bond strengths increased with RCA replacement levels and the highest values were obtained for 100% replacement of natural coarse aggregate with RCA. On the basis of a regression analysis of the experimental data, an empirical bond stress-versus-slip relationship between RCA concrete and deformed steel bars has been proposed and it has been conservatively suggested that anchorage lengths of 12 mm, 16 mm, 20 mm and 25 mm diameter deformed steel bars embedded in RCA concrete may be taken to be the same as that in natural aggregate concrete.