Assessment of the Thermal Conductivity of Sustainable Asphalt Mixtures Incorporating Crumb Rubber Via the Dry Process

Abstract Hot weather conditions increase the thermal conductivity of asphalt pavements, causing heat-related damages. Reducing thermal accumulation in pavement structures is essential to improve durability and service life. This study examines the thermal and mechanical performance of asphalt mixtures modified with crumb rubber (CR) via the dry process. Twelve modified mixtures with 1%, 3%, and 5% CR were prepared using four particle sizes (0.3 mm, 2.36 mm, 4.75 mm, and blended), along with an unmodified control mix. Thermal conductivity was measured using the QTM-500 device, while mechanical properties were evaluated via the Marshall method, including stability, flow, air voids, and voids filled with asphalt (VFA). Statistical analysis using ANOVA and Tukey HSD validated the results. Thermal conductivity decreased with higher CR content, reaching 0.4619 W/m.K at 5% CR with blended gradation – a 59.4% reduction from the baseline of 1.1389 W/m.K. Marshall stability peaked at 1% CR (14.446 kN) but declined at higher CR levels due to increased air voids, affecting compatibility. With blended gradation and 2%–3% CR, both insulation and mechanical integrity improved. In hot climates, CR use enhances thermal performance, promotes tire recycling, and offers cost-efficient pavement solutions.