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

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.