Optimizing the Physical Properties of Bitumen for Hot Areas with Recycled Additives

Since natural bitumen without additives is not suitable for creating a robust pavement structure to withstand diverse weather conditions and traffic loads, researchers have been exploring innovative methods to improve and enhance the properties of bitumen in recent years. This paper aims to optimize the composition of modified bitumen, considering the best physical performance for use in hot regions. To achieve this, the influence of four types of additives, namely Recycled Tire Rubber (RTR), Styrene-Butadiene-Styrene (SBS), reused Low-Density PolyEthylene (LDPE), and Sulfur (S), at three levels, is evaluated on the properties of bitumen using the Response Surface Methodology based on Central Composite Design (CCD). Based on the evaluations, optimal values for the additives are determined. Laboratory results demonstrate that the optimal values of the additives not only improve the penetration grade, softening point, ductility, and viscosity of bitumen but also exhibit synergistic effects. Furthermore, the addition of mineral additives significantly enhances the storage stability of the incorporated polymers in bitumen. The optimized modified bitumen, with the aforementioned properties, demonstrates an error value consistently less than 2% of the measured values, providing satisfactory performance for use in hot regions.