Engineering Emulsified Bitumen from Extracted Buton Natural Asphalt: Solid-Phase Effects on Performance Characteristics

Abstract

The engineering utilization of Extracted Buton Natural Asphalt (EB-BNA) as a raw material for emulsified bitumen offers a strategic alternative to conventional petroleum- based binders. This study evaluates the influence of solid-phase content on the performance characteristics of EB-BNA-based cationic slow-setting (CSS-1h) asphalt emulsion. Bitumen extracted from Buton rock asphalt was formulated with varying solid- phase contents ranging from 55.4% to 59.4%, while kerosene and liquid-phase components were proportionally adjusted to maintain total mixture consistency. Experimental results indicate that increasing solid-phase content significantly increases viscosity (from 15 to 106 Saybolt Furol at 25°C), residue content (from 58.6% to 75.4%), and ductility (from 42 cm to 48 cm), while reducing penetration (from 92 to 79 dmm). Emulsion instability was observed at low solid-phase content (55.4–56.4%) due to substandard viscosity (<20 SF) and at high solid-phase content (59.4%) due to excessive viscosity (>100 SF) and 24-hour sedimentation. The optimum formulation was identified at 57.4% EB-BNA and 5% kerosene, yielding viscosity of 24 SF, residue content of 64.7%, penetration of 83 dmm, ductility of 44 cm, and stable particle charge characteristics, all meeting ASTM and Indonesian SNI specifications. The findings confirm a strong correlation between solid-phase engineering and emulsion performance, demonstrating that precise control of solid-phase proportion is critical in achieving mechanical stability and specification compliance. This study provides a performance- based framework for optimizing locally sourced Buton asphalt in sustainable pavement applications.