Mechanical properties of seawater-mixed steel fiber reinforced concrete

In this study, seawater was used for the preparation of steel fiber reinforced concrete (SFRC); furthermore, the mechanical properties of the seawater-SFRC exposed to a high humidity environment-including the cubic compressive strength, axial compressive, and flexural properties-were monitored for 27 months, also considering the carbonation effect. The results revealed that the mechanical properties of the un-carbonized SFRC specimens continued to improve with increasing exposure time, and tended to stabilize after 15 months, even if blended with 20% fly ash or 20% fly ash combined with 40% slag. Moreover, the steel fibers inside the specimens did not show signs of corrosion. For the pre-carbonated SFRC specimens, the mechanical properties also improved gradually over time; however, a decrease in the axial compressive toughness and flexural properties was observed after 15 months of exposure. The carbonation effect reduced the alkalinity of the SFRC and accelerated the corrosion of the steel fibers near the specimen surface, with the thickness of the corroded layer reaching 20-30 mm at 27 months. We found that corrosion of the steel fibers inside the seawater concrete occurred when the pH was less than 10. This study could provide valuable evidence for the potential application of seawater-SFRC.