The Influence of Water Activity on the Hydration Rates of Triclinic Tricalcium Silicate

Published

January 20, 2016

Author(s)

Tandre Oey, Aditya Kumar, Gabriel Falzone, Jian Huang, Sierra Kennison, Mathieu Bauchy, Narayanan Neithalath, Jeffrey W. Bullard, Gaurav Sant

Abstract

Tricalcium silicate stops hydrating at relative humidities (RH) less than 80 %. But the rate at which its hydration rate decreases as a function of the RH has not yet been elucidated. By invoking correspondence between RH and water activity (aH, unitless), both of which are related to the chemical potential of water, the reaction evolutions of tricalcium silicate are tracked in water + IPA (isopropanol) mixtures, prepared across a wide range of water activities. Emphasis is placed on quantifying: (a) the rate of hydration as a function of aH, and (b) the critical water activity (aHc) at which hydration ceases, identified to be ≈ 0.70. The hydration of tricalcium silicate is arrested even when the system remains saturated with a liquid phase, so no negative capillary stresses develop. This suggests that changes in chemical potential induced via a vapor-phase or liquid-phase route both induce similar suppression of hydration. A phase boundary nucleation and growth (pBNG) model is fit to measured hydration rates from the onset of the acceleration period until well beyond the rate maximum when the water activity is altered. The simulations suggest that at a fixed hydrate nucleation density, water activity reductions consistently suppress the growth of hydration products. Thermodynamic considerations of how water activity changes may influence reactions/hydrate evolutions are discussed. The outcomes improve our understanding of chemical factors that influence the rate of tricalcium silicate hydration.

Citation

Journal of the American Ceramic Society

Volume

99

Issue

7

Pub Type

Journals

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DOI Link

Keywords

water activity, hydration, phase boundary nucleation and growth, cement, tricalcium silicate

Citation

Oey, T. , Kumar, A. , Falzone, G. , Huang, J. , Kennison, S. , Bauchy, M. , Neithalath, N. , Bullard, J. and Sant, G. (2016), The Influence of Water Activity on the Hydration Rates of Triclinic Tricalcium Silicate, Journal of the American Ceramic Society, [online], https://doi.org/10.1111/jace.14181 (Accessed January 19, 2025)