Influence mechanism of sulfate freeze-thaw cyclic erosion on the mechanical behavior of steel fiber reinforced high-strength self-compacting concrete

High-strength self-compacting concrete (HSSCC) meets the requirements of large construction projects for both strength and workability, and the addition of steel fibers further enhances its deformability and toughness. The components are inevitably exposed to harsh environments, and their long-term mechanical performance in such conditions undoubtedly has a significant influence on the safety of construction buildings. This paper conducted 300 cycles of sulfate freeze-thaw (SFT) erosion experiment on Grade 100 HSSCC cured for 120 days and then investigated the changes in appearance, microstructure, and mechanical behavior, clarifying the role of steel fibers in enhancing its erosion resistance. The results showed that the loss rate of mass and compressive strength of steel fiber reinforced HSSCC increased as cycles of SFT erosion increased, while they decreased with the increasing V f . Whereas the relative dynamic elastic modulus exhibited an opposite trend and remained above 0.98. During 300 cycles of SFT erosion, the HSSCC underwent three stages: microcrack generation, crack expansion, and capillary pore deterioration. The latter two were caused by the combined effect of ettringite crystal expansion and frosting swelling force. Steel fibers improved the flexural-tensile strength, initial flexural toughness, and residual flexural toughness of HSSCC subjected to various cycles of SFT erosion, particularly mitigating the deterioration of their residual flexural toughness. When V f increased from 0.3 v % to 1.2 v %, R e,300 and R e,150 of HSSCC subjected to 150 erosive cycles increased by 1.4 and 1.6 times, respectively, whereas during 150–300 cycles they improved by a factor of 1.4 and 2.1. This demonstrated that steel fibers significantly improved the flexural-tensile deformation behavior and erosion resistance of HSSCC.