The effect of seawater on the phase assemblage of hydrated cement paste: A study on PC, CAC and CSA

The present study investigates the effect of seawater on hydration of Portland cement (PC), calcium aluminate cement (CAC) and calcium sulfoaluminate cement (CSA). The cement samples were exposed to seawater at various curing ages and were characterized using thermogravimetric analysis and X-ray diffraction. The phase assemblages of the exposed samples are then compared with the unexposed samples to observe the changes that occur during the exposure to seawater. The exposure to seawater mainly affected the AFm phases in hydrated cements. The chloride uptake results in the formation of Friedel's salt. Monocarbonate, hemicarbonate and C₂AH₈ are the primary chloride binding phases in PC, CSA and CAC, respectively. Another observed effect of seawater exposure is the stabilization and formation of more ettringite in PC and CSA due to sulfate ions. The findings from these experiments are essential to better understand the phase assemblage changes that occur in structures exposed to marine environments.