Investigation of bond behaviour between recycled aggregate concrete and deformed steel bars

The results of 45 pullout tests on 8, 10 and 12 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 25, 50, 75 and 100 % are described here. Although consistent results were not obtained for the 8 mm bars, the normalized bond strengths of the 10 and 12 mm bars across all RCA replacement levels were higher for the RCA concretes compared with the natural coarse aggregate concrete, and they increased with RCA replacement levels. Brittleness index, an analogous parameter from rock mechanics, has been shown to be a relevant predictor of the measured bond strengths. An empirical bond stress-slip relationship has been proposed and it has been conservatively suggested that anchorage lengths for the 10 and 12 mm deformed bars in recycled aggregate concrete may be taken to be the same as those in natural aggregate concrete.