Atomic force microscopy study of the Microstructure of Crumb Rubber modified Bitumen

Objective. The objective of the study is to establish quantitative relationships between the parameters of a two-stage technology for bitumen modification with crumb rubber, the features of the formed microstructure, and the physico-mechanical properties of the composite material to improve the quality of road binders.
Method. The work employed the method of atomic force microscopy (AFM) for a comprehensive study of the microstructure of bitumen modified with crumb rubber using a two-stage technology, which includes a stage of preliminary rubber swelling. Topographic scanning and phase contrast modes were used to analyze surface morphology, phase distribution, and local mechanical properties.
Result. The article presents the results of a study of the microstructure of modified bitumen. The two-stage technology ensures the formation of a stable heterogeneous structure with a uniform distribution of rubber crumb particles measuring 0.5–2.0 μm in size within the bitumen matrix. A 3–5-fold increase in surface roughness was revealed compared to the original bitumen. Using the phase contrast method, the components of the composite (bitumen matrix and elastic rubber particles) were identified, and the quality of interphase interaction was assessed. The optimal rubber crumb content was determined to be 12–15% of the bitumen mass. Quantitative correlations were established: an increase in the dispersion of rubber particles by 25–30% leads to an increase in elasticity by 15–20%. The modification increases crack resistance by 25–30% and rutting resistance by 20–25%.
Conclusion. A two-stage process for modifying bitumen with rubber crumbs promotes the formation of a homogeneous heterogeneous structure with uniformly distributed elastic particles, creating a dispersed reinforcing framework. This results in a binder with improved physical and mechanical properties: increased temperature stability, elasticity, crack resistance, and rutting resistance, which is aimed at increasing the durability of road surfaces. The AFM method has proven its effectiveness in designing modified bitumen compositions with specified properties.

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