Bond behavior of confined rebar in recycled brick aggregate concrete using bending pullout test.

The pertinence of recycled brick aggregate (RBA) in concrete structures largely depends on their bonding ability with the rebars. Considering the practical detailing of concrete structures where main rebars are usually confined by stirrups, this study conducted bending pullout tests on 12 beam specimens to study the influence of concrete confinement on the bond behavior of rebar in RBA concrete. The investigated variables include RBA%, rebar diameter (d), embedment length (l_e ), and the ratio of concrete cover to rebar diameter (c/d). Bond stress-slip relationships were acquired, analyzed, and average bond strengths were compared to the AS 3600, CEB-FIP codes, and existing MacGregor's model. The average bond strength of confined specimens was nearly double that of the unconfined specimens. A progressive increase in bond strength was noticed with the presence of RBA regardless of confinement. The confined specimens also exhibited higher deformability, ductility, and toughness values than those of the unconfined beams. At 15% RBA content, the maximum toughness value of the confined specimen was 3078.1 J, while the unconfined specimens reached a value of 278.1 J, only. Similarly, the ductility of the confined beam was found in a range of 1.21-1.60 whereas the value is only 1.04-1.10 for the unconfined cases. Moreover, the confined specimens exhibited a significant number of cracks during their failure, while the unconfined specimens experienced a split type brittle failure. Nevertheless, these findings may contribute to the further development of the bond behavior of rebar in RBA-based concrete structures and thus play a role in the sustainability of construction materials.