Enhancing hysteretic behavior in rubberized reinforced concrete beams through a pre-mixing technique

Recycled rubber presents a promising approach to enhancing the seismic performance of reinforced concrete (RC) structures and promoting sustainability. Incorporating rubber into the concrete matrix can help address the environmental issue of waste tire disposal while improving conventional concrete's ductility and energy absorption. However, increasing rubber content can paradoxically reduce energy absorption. Therefore, achieving optimal bonding between rubber and cement is crucial to maximizing the benefits of rubberized concrete (RuC). This study aims to overcome these challenges by exploring the potential of a pre-mixing technique to improve the overall seismic performance of RuC structures. To this end, the study investigates the cyclic flexural response of RC beams containing 15% rubber content, focusing on a novel pre-mixing technique designed to enhance rubber-cement bonding. Mechanical experiments were conducted on specimens, including conventional concrete (CC), unmodified RuC, and pre-mixed RuC. The study analyzes the impact of rubber content and pre-mixing on the energy absorption and ductility of the flexural hinge, evaluating factors such as pinching behavior and stiffness degradation. Results demonstrate that, to achieve 70% of their ultimate strength after peak load, pre-mixed beams exhibit a 235% higher cumulative energy absorption compared to both CC and unmodified RuC beams. Notably, pre-mixed beams exhibited significantly less pinching behavior and experienced a substantial reduction in both strength and stiffness degradation (52% and 30%, respectively) during successive cycles compared to unmodified rubberized beams. Further studies are recommended to investigate the effects of mixing composition on optimizing performance.