Strength, hydration, and microstructure of seawater sea-sand concrete using high-ferrite Portland cement

The increasing construction of marine engineering is severely limited by the scarcity of raw sources of fresh water and river sand, and thus the development of seawater sea-sand concrete (SWSSC) is urgently required. However, in the marine environment, ordinary Portland cement (OPC) suffers from sulfate attack and abrasion, et al. Instead, it has been reported that high ferrite Portland cement (HFPC) has the advantages of low hydration heat, high pervious strength, high abrasion resistance, and high corrosion resistance, and thus can potentially be a great candidate for SWSSC preparation. Here, for the first time, we systematically investigate the strength, hydration, and microstructure of SWSSC based on HFPC by compressive strength, MIP, hydration heat, TGA, and SEM-EDS. The results show that seawater sea-sand can accelerate HFPC hydration more obviously than that of OPC, increasing the 3-day concrete strength by 58.9%, and effectively solving the shortcoming of low early strength. Such acceleration is mainly due to the reaction between chloride and C₄AF to form Friedel's salt. Moreover, the alkalinity of different cement pastes was measured, providing a reference for durability evaluation of FRP composites in concrete. Such findings provide fundamental insights on the feasibility of eco-friendly and corrosion-resistance SWSSC based on HFPC.