Investigation of the corrosion-induced damage mechanism of steel fibers in ultra-high-performance steel fiber-reinforced concrete using X-ray computed tomography

•The grid structure formed by interconnected steel fibers is the key to induce corrosion damage in UHPSFRC.•Corrosion of the steel fibers caused the concrete cover of UHPSFRC to crack or spall from the outside to the inside.•Areas with higher initial density of steel fibers are more prone to corrosion damage.•The denseness of the UHPSFRC cement matrix decreases as the steel fiber content increases. To investigate the corrosion damage mechanism of ultra-high-performance steel fiber-reinforced concrete (UHPSFRC), the electrically accelerated corrosion process of specimens with different steel fiber contents was evaluated using micron-level X-ray computed tomography. The results showed that the grid structure formed by the interconnecting steel fibers was a key factor in inducing corrosion damage in the UHPSFRC. The 1% steel fiber content specimens were strongly corrosion-resistant. Steel fiber corrosion triggered the concrete cover of the UHPSFRC to crack or spall from the outside to the inside, and areas with a higher initial density of steel fibers showed a higher degree of damage.