Experimental evaluation of the bond performance of deformed steel bars embedded within an engineered cementitious composite with shape memory alloy fibers under unidirectional cyclic loading

The excellent tensile properties and self-recovery capabilities of high-performance composites composed of engineered cementitious composite (ECC) and shape memory alloy fiber (SMAF) members have generated intense interest as replacement for concrete in close proximity to the steel bar reinforcement applied within reinforced concrete structures. Nonetheless, the impacts of SMAF parameters on bonding strength remain poorly understood, and the potential of SMAF for reducing residual slip at the bond interface during unloading has not been analyzed systematically. The present work addresses these issues by evaluating the bond strength and residual slip of 11 groups of pull-out specimens involving deformed steel bars embedded within ECC and SMAF-ECC matrices with different parameters under unidirectional cyclic loading. The parameters included the diameter ( D ) of the deformed steel bar (12, 14, and 16 mm), the diameter ( d ) of the SMA fiber (0.8, 1.0, and 1.2 mm), and SMAF content (0.25 % and 0.5 % by volume). The results reveal that SMAF addition substantially improves the bonding performance between the matrix and the reinforcement due to crack self-recovery. In addition, the overall bonding performance increased with decreasing D and decreased with increasing d , while doubling the SMAF content from 0.25 vol% to 0.5 vol% exhibited only a modest increase in the bonding performance. Meanwhile, the greatest slip recovery performance is obtained for the composite specimen with d = 1.2 mm and an SMAF content of 0.25 vol%. Accordingly, this study offers essential support for evaluating the slip self-recovery performance at the SMAF-ECC and rebar bond interface.