New Insights Into the Effect of Calcium Hydroxide Precipitation on the Kinetics of Tricalcium Silicate Hydration

Published

July 8, 2010

Author(s)

Jeffrey W. Bullard, Robert J. Flatt

Abstract

Particles of tricalcium silicate in water typically exhibit a relatively quiescent period (called Stage II) shortly after wetting, lasting up to several hours and during which little apparent reaction occurs. Stage II frequently terminates at about the same time that calcium hydroxide first precipitates from the solution. The close correspondence between these two events led to an early theory that calcium hydroxide precipitation actually triggers a period of accelerating hydration (Stage III), a theory which later gave way to experimental evidence that was thought to contradict it and other theories which were deemed more satisfying from a mechanistic standpoint. This paper surveys several theories and critical experimental data on early-age hydration kinetics of tricalcium silicate. Using HydratiCA, a kinetic cellular automaton model of cement hydration and microstructure development, we investigate two of the leading hypotheses on the mechanism of slow hydration in Stage~II, and see for each one the implications of suppressing the growth of calcium hydroxide formation. Each hypothesized mechanism leads to quite different kinetic behavior when calcium hydroxide is suppressed, a result which indicates a line of future experimental inquiry that could decisively determine the Stage~II mechanism. Furthermore, the simulations demonstrate how the early theory of calcium hydroxide triggering might be reconciled to the more modern theoretical models and to the experimental data.

Citation

Journal of the American Ceramic Society

Volume

93

Issue

7

Pub Type

Journals

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Keywords

cement, concrete, hydration, computer simulation, building technology

Citation

Bullard, J. and Flatt, R. (2010), New Insights Into the Effect of Calcium Hydroxide Precipitation on the Kinetics of Tricalcium Silicate Hydration, Journal of the American Ceramic Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=903797 (Accessed July 26, 2024)