Influence of calcareous sand powder and water environment on macro- and micro-properties of ferroaluminate cement

The deterioration of engineering structural performance caused by seawater erosion, along with the scarcity of conventional construction materials, are significant challenges in contemporary island construction. Therefore, this study investigates the macro- and micro-properties of ferroaluminate cement mixed with calcareous sand powder (FAC-CSP) in three distinct water environments (FF: Freshwater mixing and immersion, FS: Freshwater mixing and seawater immersion, and SS: Seawater mixing and immersion) and elucidates the synergistic mechanism among the components. The results demonstrate that CSP alters the electrochemical properties of specimens in both FS and SS environments, while it does not significantly affect specimens in the FF environment. Additionally, CSP notably increases the resistivity of specimens at the later stages of hydration. Although CSP leads to a reduction in the mechanical properties of the specimens, it contributes to strength enhancement during the later stages of hydration. Seawater immersion significantly improves the strength of the specimens, compensating for the strength loss induced by CSP. Specimens in FS and SS environments exhibit higher ettringite content, and the presence of CSP promotes more complete hydration of FAC. Seawater immersion significantly increases the bound water content in the specimens. The adsorption of CSP particles and the ionic contribution of seawater stimulate the formation of additional hydration products around the CSP particles. This process fills the gap between the CSP particles and the specimen matrix with hydration products. These findings offer micro-scale insights into the roles of CSP and seawater in FAC hydration.