Sustainable application of recycled brick aggregates in concrete: evaluation of mechanical, durability, and environmental properties

Abstract This study presents a comprehensive and novel investigation into the environmental sustainability and mechanical behavior of concrete incorporating three classifications of waste tyre rubber—powder, crumb, and chips—as partial replacements for natural aggregates. In contrast to prior research that typically focuses on a single rubber type or limited replacement ranges, this work systematically evaluates the influence of various rubber forms across a full spectrum of inclusion levels, ranging from 0% to 30% in 5% increments. Concrete mixtures were prepared with two distinct water-to-cement (w/c) ratios (0.4 and 0.5) to examine the interaction between mix design parameters and rubber content. Mechanical properties such as compressive strength, ultrasonic pulse velocity (UPV), and dynamic modulus of elasticity were assessed after both 28 and 90 days of curing. Notably, the mix containing 5% rubber at a 0.4 w/c ratio (0.4WR5) achieved a peak compressive strength of 58.81 MPa at 90 days, while the 8% rubber mix exhibited the highest UPV of 5660 m/s challenging the conventional perception that rubber addition invariably degrades concrete performance. These findings demonstrate that optimized rubberized concrete mixes, particularly at 5–10% inclusion levels, can deliver high strength and enhanced durability characteristics, contributing to sustainable construction without compromising structural integrity. Furthermore, the study highlights the critical influence of curing time and w/c ratio on the behavior of rubber-modified concrete, offering valuable design guidance for engineering applications. By effectively utilizing waste tyre rubber, this research contributes to circular economy principles and the reduction of concrete’s environmental footprint, presenting a practical route for diverting rubber waste from landfills.