Performance Evaluation of Rubber Modified Asphalt Mixtures with Two Typical Light Oils: A Comparative Study Between Aromatic and Tall Oils

Recycling waste rubber is essential for promoting circular economy practices, reducing environmental pollution, and conserving resources. This study examines the performance of crumb rubber-modified asphalt mixtures incorporating two light oils (aromatic oil and tall oil) to alleviate the high viscosity and poor workability of asphalt with high rubber content. Mixtures were prepared using a neat asphalt modified with 20% crumb rubber and 5% light oil (by mass of the neat asphalt), combined with basalt aggregate in an AC-13 gradation. High-temperature performance was evaluated via Marshall stability and wheel tracking tests at 60 °C, moisture sensitivity through immersion Marshall and freeze–thaw splitting tests, and low-temperature cracking resistance using semi-circular bending (SCB) tests at 15 °C. Tensile strength and fatigue life were measured by splitting tests at 25 °C and fatigue tests at 15 °C, respectively. Results indicate that the rubber-modified mixtures showed significant improvements: the total deformation decreased by 44.7% and 64.1% for aromatic oil- and tall oil-modified mixtures, respectively, compared to the neat asphalt. Fracture toughness increased by 46.5% and 71.9%, and tensile strength improved by 40.2% and 63.6%, respectively. At a low stress ratio (0.281), mixtures with tall oil exhibited a 47.9% longer fatigue life than those with aromatic oil. Tall oil demonstrated superior performance, attributed to enhanced rubber swelling and crosslinked network formation, which improved viscosity and aggregate coating. The findings confirm that light oil-modified rubber asphalt mixtures, especially those containing tall oil, present a viable approach for developing high-performance and environmentally sustainable road pavements.