Impact resistance and low-carbon potential of concrete using rubber from scrap tires

The accumulation of end-of-life tires has become a critical environmental challenge, as most discarded tires are still disposed of in landfills, generating long-term risks to human health and natural ecosystems. Utilizing recycled rubber particles as a partial substitute for natural aggregates offers a practical approach to waste valorization while reducing the environmental burden of concrete production. This study evaluates the mechanical and impact-related performance of fine-aggregate concrete in which river sand is replaced by recycled rubber sand derived from processed scrap tires. Five mixtures were produced with a constant water-to-binder ratio of 0.35 and rubber replacement levels of 0%, 10%, 20%, 30%, and 40% by volume. A series of tests was carried out to determine compressive strength, flexural strength, rebound energy absorption, and impact resistance under both drop-weight and flexural loading. The results indicate that strength decreases progressively with increasing rubber content, with reductions of up to approximately 66% at the highest replacement level. In contrast, the energy absorption capacity increases slightly, from 4.69 J for the control mixture to 4.83 J at 40% rubber content. Among the tested mixtures, the 10% replacement level exhibited the highest impact resistance, suggesting a balance between ductility and residual strength. A simplified environmental assessment based on Global Warming Potential (GWP) indicates that incorporating recycled rubber can reduce CO 2 emissions due to the partial replacement of natural aggregates. Overall, the results suggest that rubberized fine-aggregate concrete may offer potential benefits for applications requiring improved impact performance and reduced environmental impact, although its use should be carefully considered in view of the associated strength reduction.