Experimental investigation of dynamic splitting tensile damage behaviours of steel fibre ceramsite concrete in freeze–thaw environments

Ceramsite concrete is widely used in cold region infrastructure, but its poor freeze–thaw resistance under dynamic loading limits its service performance. This study innovatively investigates the freeze–thaw damage, dynamic splitting tensile properties and crack characteristics of steel fibre ceramsite concrete (SFCC) by combining Brazilian disc splitting tensile tests and acoustic emission (AE) monitoring. Specimens with four steel fibre contents (0, 0.6, 1.2, 1.8%) were subjected to 0, 50, 75, 100 freeze–thaw cycles and four loading rates (0.002, 0.02, 0.2 and 2 mm/s). Results show that steel fibre significantly improves the frost resistance of SFCC; after 100 freeze–thaw cycles, the mass loss rate is reduced by 48.1% and the dynamic elastic modulus is increased by 9.32 GPa at 0.6% fibre content. The dynamic splitting tensile strength first increases and then decreases, reaching the maximum at 1.2% fibre content. Steel fibre raises the proportion of shear cracks, while freeze–thaw cycles promote tensile cracks, and AE analysis confirms that steel fibre delays micro-crack penetration. This work reveals the damage mechanism of SFCC under coupled freeze–thaw and dynamic loading, providing quantitative guidance for cold-region engineering applications.