Salt freeze-thaw resistance and damage evolution model of concrete reinforced with corrosion-resistant coated steel fiber

The coupling effect of detrimental ion erosion and freeze-thaw (F-T) cycles poses substantial safety and durability issues for concrete structures in cold regions. This study aimed to enhance the anti-spalling property and service life of construction under this coupling effect by incorporating the corrosion-resistant coated milled-cut steel fiber (MSF) into concretes. Long-term F-T cycles were performed on milled-cut steel fiber reinforced concrete (MSFRC) of variable fiber content (0.6 %, 1 % and 1.4 %) in a 3.5 % NaCl solution. The physical and mechanical properties of MSFRC were investigated, as well as evaluating the microscopic morphology of the fiber-concrete interface using scanning electron microscopy (SEM). The results indicated that MSF contributed to mitigating the matrix spalling and fiber corrosion, particularly in larger-sized structural members with a fiber content of 1 %. With salt F-T cycling, MSFs exhibited superior corrosion resistance and favorable bonding to the substrate, thus reducing fatigue damage induced by the F-T cycles. The compressive and splitting tensile strength loss rate could be kept below 25 % following 100 salt F-T cycles, accompanied by a transformation in the failure mode from matrix rupture to ductile fracture. Empirical formulae for strength prediction based on fiber content and F-T cycle numbers were developed, with R² exceeding 0.98. Finally, a damage model was established to serve as a reference for designing MSFRC service life under salt F-T cycles. MSFRC with 1 % fiber content is considered optimal for durability in cold marine environments and can withstand up to 227 cycles.