Combined elevated-rate and cyclic loading performance of strain-hardening cementitious composites

Strain-hardening cementitious composites (SHCC), known for their advanced ductility and toughness, are promising for applications subjected to dynamic or cyclic loads. However, the combined effects of non-quasi-static loading rate and cyclic action—termed elevated-rate-cyclic loading—remain underexplored. These conditions are critical for simulating real-world forces such as seismic and traffic loads, where rate- and cycle-induced damage mechanisms interact and can significantly impact material performance. This study investigates two polyvinyl alcohol-SHCC mix designs, M45 and F28 (fly-ash-to-Portland-cement-ratio of 1.2 and 2.8 respectively), under elevated-rate-cyclic flexural loading. One-side cyclic and reversed cyclic regimes were applied across different loading rates to assess their effects on strength, ductility, stiffness, and toughness. The effect of mix design on SHCC responses is analysed through micromechanical models with microscopic observation of failure patterns. Results show that elevated-rate-cyclic loading caused greater reduction in SHCC ductility compared with cyclic or high-rate loading alone (by 45 % for M45 and 36 % for F28 versus quasi-static monotonic loading), due to accelerated fibre-matrix interface degradation and increased fibre rupture. F28, with lower matrix and interfacial bonding strength relative to fibre strength, exhibited better rate-cyclic endurance than M45 in sustaining strength, ductility and toughness. Material design insights are thereby provided for mitigating negative elevated-rate-cyclic effects and enhancing SHCC resilience.