Experimental and analytical study of bond behavior between recycled aggregate concrete and steel bars using a pullout test

The paper presents the results of an experimental program carried out on 96 concrete pullout specimens prepared with natural and recycled aggregates using 10 and 12 mm diameter deformed steel bars. Steel rebars were concentrically embedded in pullout specimens with two embedded length of 5 and 10 times the rebar diameter. The present work includes six recycled concrete aggregate mixtures and two conventional concrete mixtures with C25/30 and C35/45 target class of compressive strength and S4 class of workability. For both series, specimens were fabricated with different incorporation ratios of fine and coarse recycled aggregates and only coarse recycled aggregates. Tensile load was applied gradually until the pullout failure occurred and the slip between the rebar and concrete was measured at the free and loaded ends for each loading level. Furthermore, systematic observations of failure surface have been made at both macroscopic and microscopic scales. Test results showed that for the same class of compressive strength the bond strength and related failure mechanisms remain very close and the obtained values are, at least, four times higher than the predicted values by Eurocode 2. The experimental results of this study, together with an extensive number of results reported in the literature, were used to describe the variation of bond strength with concrete compressive strength, embedded length, and concrete cover. In addition, an analytical bond‐slip relationship is proposed and the parameters of bond‐slip law were calibrated by an optimization algorithm.