Evaluation of bond strength of bonded-in or post-installed reinforcement

This paper reports on a research program conducted at the American University of Beirut (AUB) to assess the effect of several variables on the performance of frame nodes with cast-in and post-installed reinforcement, and thus to evaluate the performance of different injection systems used in bonding-in reinforcement. Eighteen fill-scale specimens were tested in five sets. For each of two different bar sizes (12 or 14 mm), two different nominal concrete strengths (15 or 20 MPa), and three different embedment lengths (150, 250, or 290 mm), three or four companion specimens were tested in each set. The variables within each set were the installment history (pre-installed or post-installed), the anchorage type of the pre-installed or cast-in bars (hooked or straight), and the adhesive mortar used in the post-installing procedure. The test specimen simulated the rigid connection of two cantilever beams to a wall or column. An evaluation and comparison of cracking patterns, load-deflection curves, and bond strength values indicated that post-installed straight bars using appropriate adhesive mortars developed, in general, greater bond strength than companion cast-in straight bars, especially in the case of relatively shorter anchorage length. Also, test results indicated that ultimate strength of post-installed straight bars can be predicted with good precision by careful strut-and-tie modeling of the node.