Enhancing Pavement Performance and Economy through Crumb Rubber Modified Bitumen: A Sustainable Engineering Approach

The reuse of waste materials in infrastructure is a growing focus in materials engineering for enhancing both performance and sustainability. This study modified a conventional 60/70 penetration grade bitumen with crumb rubber derived from waste tires. Crumb rubber was incorporated in varying proportions (4%, 8%, 12%, 16% by weight of bitumen) using a controlled wet process at elevated temperature. The modified binders and resultant asphalt mixes were then evaluated through standard laboratory tests (penetration, softening point, ductility, flash/fire point) and Marshall mix design procedures. Results indicate that a 10% crumb rubber content is optimal, yielding significant improvements in binder properties and mix performance. The 10% Crumb Rubber Modified Bitumen (CRMB) exhibited a 25% reduction in penetration and 50% reduction in ductility (indicating increased stiffness), along with a 10–12% increase in softening, flash, and fire points, signifying enhanced thermal stability and safety. Marshall stability of the asphalt mix improved by about 25% with CRMB, while the optimum binder content was 0.6% lower than that of the control mix, reflecting more efficient binder usage. CRMB also showed superior viscoelastic behavior and a higher fatigue life compared to the unmodified binder, indicating better long-term performance under cyclic loading. Economically, the use of CRMB is advantageous: approximately 8% lower binder material cost was observed for a typical pavement section, owing to reduced bitumen requirements and the substitution of cheaper recycled rubber. These findings demonstrate that incorporating waste tire rubber can transform conventional bitumen into a more durable, thermally stable, and cost-effective paving material, contributing to sustainable infrastructure development.