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.
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