Fatigue Behavior of Buton Asphalt Modified with Marine Fuel Oil and Styrene-Butadiene Rubber

The service life of asphalt pavements is strongly influenced by their fatigue resistance, especially in tropical regions where high temperatures accelerate binder hardening. Conventional mix design methods often fall short in addressing this issue, highlighting the need for performance-based approaches. This study evaluates a Modified Asphalt (MA) binder produced from Extracted Buton Asphalt (EBA) and enhanced with 12% Marine Fuel Oil (MFO) and 2% Styrene-Butadiene Rubber (SBR). Asphalt mixtures were prepared with 6% binder and 94% aggregates using five MA–PA combinations: 0/100, 25/75, 50/50, 75/25, and 100/0. Cylindrical specimens were compacted using the Marshall method and tested for fatigue performance under repeated loading with a Dynapave UTM-30. Fatigue behavior was examined through resilient modulus, accumulated strain, and fatigue life. The results demonstrated that low MA contents (≤25%) reduce cohesion and fatigue life due to MFO-induced softening. Intermediate MA levels (50–75%) exhibit a synergistic MFO–SBR effect, improving recovery and durability. At 100% MA, excessive stiffness leads to early cracking. The best performance occurs at 75% MA, where stiffness and flexibility are optimally balanced in accordance with the Balanced Mix Design (BMD) concept. Overall, MA derived from EBA with MFO and SBR demonstrates strong potential for heavy-traffic pavements in tropical climates. However, given that the current study was limited to laboratory conditions, further field validation and mechanistic–empirical modeling are proposed to refine long-term performance predictions.