Sustainable Rubberized RCC Using Locally Sourced Waste Rubber Tire Powder and GGBFS-Based Binder

This study investigates roller-compacted concrete (RCC) in which fine aggregate was replaced with waste rubber tire powder (WRTP) at 0-16% by volume, using a binder containing 40% ground granulated blast-furnace slag (GGBFS). Fresh, mechanical, transport-related, microstructural, and environmental aspects were evaluated. While WRTP reduced workability, density, and ultrasonic pulse velocity (UPV), UPV values remained within the "excellent" classification range. Among the investigated mixtures, 2% WRTP provided the most favorable overall performance, increasing the 28-day compressive strength from 26.6 to 28.2 MPa, the 90-day compressive strength from 31.1 to 37.8 MPa, the flexural strength from 3.33 to 3.47 MPa, and the splitting tensile strength from 1.81 to 2.37 MPa. The 2% WRTP mixture also reduced the secondary capillary absorption coefficient by approximately 32.3%, from 0.00127 to 0.00086 mm/√s. Higher WRTP contents progressively decreased compressive strength and static modulus of elasticity, whereas flexural strength was comparatively less affected. SEM/EDS observations revealed more pronounced interfacial voids and discontinuities at higher WRTP contents, consistent with the observed performance decline. A simplified cradle-to-gate embodied-carbon assessment indicated that the 40% GGBFS binder substitution was the primary contributor to the estimated carbon reduction, with the reference and 2% WRTP mixtures exhibiting approximately 33.4% and 33.1% lower embodied carbon, respectively, than the hypothetical cement-only RCC baseline. In addition, the 2% WRTP mixture incorporated 6.43 kg/m³ of waste tire-derived rubber, providing an additional waste-utilization benefit. Overall, low WRTP incorporation, particularly at 2%, combined with a GGBFS-based binder provided a favorable balance between engineering performance, reduced embodied carbon, and waste utilization under the investigated conditions.