Workability, strength, and shrinkage of ultra-high-performance seawater, sea sand concrete with different OPC replacement ratios

An experimental investigation on the chemical, physical, mechanical, and shrinkage of seawater and sea sand-based ultra-high-performance concrete (UHP-SWSSC) with supplementary cementitious materials (SCM) (i.e. slag and silica fume) is reported. Several mixes were designed with varying proportions of SCMs (25%, 37.5%, 50%, and 62.5% of binder), aggregate source, and water-to-binder ratio. Heat evolution, density, workability, compressive strength development, and long-term autogenous and drying shrinkage of UHP-SWSSC were monitored. Seawater accelerates cement hydration as reflected in the heat evolution, and consequently, dictates the early-age strength, and autogenous shrinkage. SCM addition although limits the early-age strength development offers a comparable 90 days strength. The chloride content increases from marine resources and may limit the application to nonstructural components. Nonetheless, a UHP-SWSSC mix with 50% OPC replaced by 37.5% slag and 12.5% silica fume is recommended in this study, which can achieve satisfactory workability, long-term strength, and shrinkage properties.