Influence of Seawater on the Morphological Evolution and the Microchemistry of Hydration Products of Tricalcium Silicates (C₃S)

Abstract

The current work investigates the influence of seawater on morphological properties during the hydration process of tricalcium silicate (C3S) at 3, 7, 14, and 28 days to better understand the effect of salinity (highly soluble salts) of seawater on the microstructural evolution of hydration products. The mechanism of the chemical reaction of highly soluble salts, e.g., Na2SO4 and CaCl2, with hydrated C3S was also demonstrated. The presence of highly soluble salts in seawater accelerates the hydration of C3S significantly due to releasing a significant amount of Ca2+ ions from the hydrated C3S (as CH and CSH), which participated in the chemical reaction to produce a certain amount of gypsum crystals that was more than that in distilled water, which has been shown by SEM characterization. TEM analysis revealed the growth of sharp rod-like CaSO4·2H2O crystals together with some thin and tiny wrinkled CSH that formed. Seawater promotes the hydration of C3S, pointed out by the expedited heat flow and raised heat of hydration. FTIR spectroscopy has been used to characterize and observe the dynamics of variation in the formation of calcium silicate hydrate (CSH), portlandite (CH), and gypsum (Gy) throughout the hydration process of C3S with seawater in comparison with distilled water. XRD analysis revealed that the peak intensities of the portlandite and gypsum of the hydrated C3S in seawater are higher than the comparable peaks in distilled water.

Improvement of the Hydration Kinetics of High Ferrite Cement: Synergic Effect of Gypsum and C3S–C4AF Systems

“…The HFC system with 5 mass% gypsum is properly sulfated, as the characteristic peak of the aluminate reaction occurs after C 3 S, and a similar phenomenon was also observed by Karen L. Scrivener, and it is suggested that the dosage of gypsum in the system can modify the interaction between aluminates and C 3 S. 16 In the case of properly sulfated conditions, gypsum can adjust the fast reaction of aluminate and alleviate the adsorption effect of Al 3+ ions on C 3 S, accelerating the hydration process of C 3 S. 25,26 The accumulated heat curves also revealed that the addition of gypsum promoted the hydration rate of HFC (a higher slope of the curve).…”

Mechanisms on Accelerating Hydration of Alite Mixed with Inorganic Salts in Seawater and Characteristics of Hydration Products

“…In this study, the same high water/binder ratio (10) was adopted as the previous study . With such a high ratio, the complete reaction of alite would be promoted, and the hydration products could be easily characterized …”

“…Yassen et al explored the effects of seawater on the morphology of hydration products of C 3 S pastes. It was found that the addition of seawater contributed to the formation of gypsum with a sharp rodlike morphology . However, the research mainly focused on the effects of SO 4 2– , and the effects of other single salts in seawater were not further studied.…”

Production and Characterization of GRC-SWCNT Composites for Shell Elements

“…Hydration of tricalcium silicate (3CaO⋅SiO2) in Portland cement-based materials is a process involving certain reactions. The most important of these reactions is the formation of portlandite (Ca(OH)2) and calciumsilicatehydrate (CSH) gel [68]. Portlandite is the result of hydrolysis of tricalcium (C3S) and dicalcium (C2S) silicates after a few hours when Portland cement is combined with water, forming hexagonal crystal plates of about 40 µm in a solid phase.…”

“…CSHgel is a cement product with many important engineering properties that ensure the strength of the matrix. There are two types of CH; hexagonal crystals and fine amorphous grains closely adsorbed on the CSH-gel surface [68].…”