Enhancement of the impact resistance of concrete by rubberized concrete overlays

This study investigates how rubberized concrete overlays enhance the impact resistance of substrate concrete. Drop-weight impact tests were conducted to assess the effects of rubber particle size, rubber content, and interface roughness on impact failure modes and life. A two-parameter Weibull model was applied to predict impact life. Fine rubber particles improve stress distribution and delay crack initiation, whereas coarse particles enhance energy absorption through crack deflection and interfacial slip. Rubber content governs the formation of an energy dissipation network. At 15% content, isolated particles provide limited protection, while at 30% content, a continuous network significantly slows crack propagation. Interface roughness also plays a critical role. Low roughness (Rₐ = 0.31 mm) leads to rapid crack penetration, whereas moderate roughness (Grade III, Rₐ = 0.83 mm) improves bonding and extends post-cracking life. The Weibull model reliably fits the impact data with all R² values above 0.9. Predicted lives at 5%, 15%, and 30% failure probabilities provide practical design references. These findings highlight the synergistic effects of the three factors, offering a theoretical basis for designing impact-resistant rubberized concrete overlays.