Dynamic toughness of rubberized self-compacting concrete based on SHPB and drop-weight impact tests

Impact-resistant rubberized self-compacting concrete (RSCC) was developed for China Railway Track System III (CRTS III) slab ballastless-track filling layers by replacing 10–30 vol.% of fine aggregate with rubber filaments or 20–40 and 40–60 mesh particles. The effects of rubber morphology and replacement ratio on workability, compressive strength, and impact responses under SHPB and repeated drop-weight loading were examined; the impact responses were related to multiscale structural and interfacial characteristics using X-CT, SEM/EDS, and nanoscratch. Rubber incorporation enhanced impact performance and energy absorption. RSCC with 40–60 mesh particles at 30% replacement showed the most favorable response: dynamic increase factor, normalized energy absorption index, normalized cumulative input energy, and impact toughness increased by 90.3%, 142.2%, 87.3%, and 76.0%, respectively. An interconnected rubber–void network and compliant interfaces promoted crack deflection, stress buffering, and frictional dissipation. These findings provide a scientific basis for selecting rubber morphology and replacement ratio for impact-resistant RSCC filling-layer materials.