Investigation of rheological properties of bitumen with calcium naphthenate additives

This study investigates the effect of calcium naphthenate obtained from alkaline waste of oil-refinery processes on the physical, mechanical, and rheological properties of BND 60/90 road bitumen. The proposed additive is considered as a waste-derived surfactant modifier aimed at improving the structural behavior and adhesion properties of bitumen used in road construction. Bitumen samples containing 5, 10, and 20 wt.% calcium naphthenate were prepared and tested in the temperature range of 40-140 °C using rotational viscometry. The results showed that calcium naphthenate affects the flow behavior of bitumen by increasing viscosity and promoting structure formation, especially at temperatures below 100 °C. The most effective modification range was found to be 5-10 wt.%, where improved adhesion to mineral materials and enhanced rheological stability were observed without excessive loss of penetration. The findings demonstrate that calcium naphthenate obtained from refinery alkaline waste can be used as a promising functional additive for bitumen modification and waste valorization.