A review on ultra-high performance seawater sea sand concrete: Hydration, microstructure and properties

Some research has been conducted on ultra-high performance seawater sea sand concrete (UHPSSC) in response to the shortage of freshwater and river sand in coastal regions. However, utilizing seawater and sea sand presents a multifaceted challenge. This paper reviews the properties of seawater and sea sand, elucidating their impact on hydration, microstructure, and properties of UHPSSC. The results indicate that salt ions in seawater and sea sand expedite the early-stage hydration, refining the pore structure and reducing the thickness of the ITZ of UHPSSC. It also exacerbates the self-shrinkage and dry shrinkage. Compared to ultra-high performance concrete (UHPC), UHPSSC exhibits early strength, especially at 1 d. However, the comparative conclusions for strength at 28 d are inconsistent, which may be related to the factors such as SCMs, w/b ratio, and s/b ratio. UHPSSC demonstrates excellent durability including resistance to carbonation, frost, chloride attack, and sulfate exposure. Limited literature suggests that the steel fibers within the UHPSSC are in a corrosion-free steady state for a short time (0-1080d). The low permeability of the UHPSSC reduces the diffusion of water, oxygen, and chloride ions, effectively mitigating chemical corrosion caused by sea salt. However, steel fiber corrosion in cracked UHPSSC deserves more attention.