Optimization of Ethylene – Vinyl Acetate Dosage for Rheological and Physico-Mechanical Properties of Loda Bitumen

Abstract

Heavy reliance on road transportation, especially in developing countries, has necessitated the construction of durable roads using localized materials such as natural bitumen. However, using natural bitumen as a binder in pavement construction gave poor performance and hence, the need for its modification prior to application. This study investigated ethylene–vinyl acetate (EVA) as a modifier and optimized its dosage for improved rheological, physical, and mechanical properties of Loda natural bitumen. A D-optimal mixture design coupled with Response Surface Methodology (RSM) was deployed for evaluating the effect of EVA content (1.5–6 wt%) on penetration, softening point, ductility, viscosity, and flash point. Thirteen experimental runs were analyzed using ANOVA to develop predictive and experimentally validated models. The result showed that EVA modification reduced penetration, increased softening and flash points, enhanced ductility, and reduced the viscosity of the base Loda bitumen. Multi-objective optimization identified an optimal composition of 95.6 wt% bitumen and 4.4 wt% EVA, yielding a penetration of 17.95 mm, softening point of 59.79 °C, ductility of 117.32 cm, flash point of 290.25 °C, and viscosity of 2658.22 MPa·s. These results demonstrate that optimized EVA modification significantly enhances Loda natural bitumen, supporting its use in durable pavements and promoting sustainable utilization of local bitumen resources.