Thermal Stability and Moisture Resistance of Bitumen Composites Modified with Triglyceride Plant Oils

Abstract This paper examines the chemical characteristics of four plant‐derived bio‐oils, including waste cooking oils, to address a research gap concerning their effects on the thermal stability and moisture susceptibility of asphalt. While bio‐oils are known to soften asphalt, their specific impact on these properties is less understood. The study evaluates four different bio‐oils (B1–B4) derived from various waste vegetable sources to determine their influence on asphalt performance. The findings indicate that bio‐oils with higher purity and lower polyunsaturated fatty acid content offer better resistance to heat and UV‐induced degradation. Bio‐oils with lower iodine values also show improved resistance to moisture damage. Notably, bitumen composites containing bio‐oil B2 do not negatively affect asphalt's moisture resistance, while others increase its moisture susceptibility. Tests with liquid anti‐strip agents reveal that silanes and amine‐based agents are the most effective at reducing moisture damage. These results underscore the importance of selecting bio‐oils with low acid and iodine values, low polyunsaturated fatty acid content, and high purity for use in asphalt. This study supports sustainability and resource conservation by recommending bio‐oils that preserve the durability of bio‐modified asphalts.