Effect of cover on bond strength of structural concrete using commercially produced recycled coarse and fine aggregates

Abstract While using recycled concrete aggregates in concrete, the bond efficiency with deformed rebar may be different compared to regular concrete and requires in-depth investigation. In this study, 20 beam-end specimens were tested using commercially produced recycled coarse and fine aggregate. The study used two rebar covers as parameters (25 mm and 40 mm) with a 15 M test bar and a constant bond length of 200 mm. It was observed that the average bond strength was conservative and exceeded the calculated bond strengths for both the natural and recycled concrete when compared to the existing design guideline and empirical models. In addition, two simplified descriptive bond model equations were proposed for determining the bond strength, which illustrated the functional relationship of ½ and ¼ with the compressive strength of concrete. The present study shows that the current design codes and empirical equations found in the literature are conservative while designing structures with recycled concrete.