Aidar Kengesbekov, Alfira Sabitova, Temirlan Kusainov, Zhanna Sharipkhan, Gulzat Aitkaliyeva, Moldir Ualkhanova
The development of more sustainable asphalt materials requires modified bitumen binders that combine thermal resistance, adhesion, and deformation capacity. In this study, soft paving-grade bitumen was modified with styrene-butadiene-styrene polymer, oil refinery sludge, titanium slag, and lead-furnace cyclone dust. Binders with bitumen-to-modifying-system ratios from 90:10 to 60:40 were characterized by FTIR, TGA/DSC, XRD, and portable XRF analyses and evaluated using penetration-type consistency, softening-point, qualitative adhesion, and tensile deformation tests. The modifying-system content produced non-monotonic changes in binder properties. Among the investigated formulations, the 75:25 composition provided the most balanced response, with a penetration depth of 8.6 mm, a softening point of 65.0 °C, a maximum elongation of 355.66 mm, and high qualitative film retention on mineral aggregate. In contrast, the 60:40 binder showed increased penetration and the lowest elongation, indicating that excessive modifier loading was unfavorable. The 75:25 binder was subsequently used in small-scale asphalt concrete sections and showed acceptable preliminary behavior during mixture preparation, placement, and compaction. The results demonstrate composition-dependent relationships in the investigated multicomponent system and support further evaluation of selected industrial by-products in modified bitumen binders.