Transesterification of Waste Cooking Oil to Produce A Sustainable Rejuvenator for Aged Asphalt

Abstract

This study examines the merits of esterification of waste cooking oil to reduce its acidic content for use as a rejuvenator for aged asphalt. It further examines how acidic compounds in bitumen increases the moisture susceptibility of bituminous composites made from siliceous stones and bitumen. While some acidic compounds are inherent in bitumen, the recent widespread use of bio-modifiers such as waste cooking (vegetable) oil has further increased the acidic compounds in bio-modified bitumen. Acidic compounds adsorb well to siliceous stones, but they are easily replaced by water molecules, giving rise to moisture damage. It was found that a reduction or removal of the acidic compounds of waste cooking oil via transesterification significantly enhances its resistance to moisture damage. The study results showed that treated waste cooking oil is not only a promising rejuvenator to be used with aged bitumen, but also quite resistant to moisture damage. It was also found that transesterification reduces the acid value of bitumen from 12 to 0.27 (mg KOH/g). This turned a moisture-susceptible bitumen to nearly a moisture-resistant bitumen as evidenced by nearly no change in moisture-induced shear thinning after 24hr water conditioning. The outcome of the study shows significant role of acidic compounds in moisture damage, and the importance of accounting for the acidity of rejuvenators to ensure their durability. The study results confirm the feasibility of tuning waste cooking oil to a sustainable asphalt rejuvenator to promote both resource conservation and asphalt recycling.