EFFECT OF DIFFERENT CRUMB RUBBER SIZES ON IMPROVEMENT OF BUTON ROCK ASPHALT MODIFIED

Abstract

Buton Rock Asphalt contains 20–30% asphalt, and the rest is granular material, so its use is limited due to low penetration value. Mineral granules must be included as aggregates. This study optimizes Buton Rock Asphalt with Waste Engine Oil as a softener and Crumb Rubber from tire waste. Study of Crumb Rubber sizes consists of Large (0.297–0.149 mm), Medium (0.148–0.0075 mm), and Small (<0.0075 mm), each sequentially added to the Buton Rock Asphalt modified. Tests included asphalt physical properties, volumetrics, Marshall properties, viscosity, and modeling using Response Surface Methodology. Crumb Rubber contains the most significant elements of Carbon, 67.57% and oxygen, 21.75%, with small amounts of silicon, potassium, calcium, and copper. The optimum value of Crumb Rubber content based on size is known to be 8% for CR-Large, 5% for CR-Medium, and 1.75% for CR-Small. The lower the Viscosity on Temperature Sensitivity value, the more stable the viscosity to temperature changes, with the following values: CRS (–3.997, CRL (–3.523), and CRM (–3.151). The CRS size type showed the highest Residual Stability Index, meaning it has the resistance to temperature and water changes. Multivariate Polynomial Regression analysis results showed that the addition of CR to BRAM significantly affected the volumetric asphalt concrete mixture. All regression models exhibited a high fit, with R² values ​​ranging from 0.95 to 0.98 (p < 0.0001). This study is limited to short-term laboratory tests; the performance of Petroleum Asphalt with the involvement of 30% Rock Asphalt still needs further study.