The Influence of Sodium and Potassium Hydroxide on Alite Hydration: Experiments and Simulations

Abstract

The basic nature of alkali hydroxides (NaOH, KOH) when added to mixing water, increases the pH in proportion to the level of salt addition. For alite (impure tricalcium silicate; MIII-Ca3SiO5) hydration, this pH increase accelerates the rate of hydration and reduces the duration of the induction, acceleration and deceleration regimes. This study evaluates alite hydration in solutions of varying compositions and alkalinities (0.1 M, 0.2 M and 0.5 M NaOH and KOH) in context of their heat release behavior and analysis of the solid/liquid phases. The modeling platform, µic, is used to simulate, describe and discriminate the impact of the pore solution chemistry and reaction product formation parameters on alite hydration (Bishnoi and Scrivener, 2009 [1]). Numerical predictions of the solid and liquid phase compositions and the heat release response show good agreement with experimental determinations. The simulations indicate that the effects up to the end of the induction period follow directly from a change in the pore solution composition under a solution controlled dissolution mechanism, which leads to the faster precipitation of portlandite. The changes in the main heat evolution peak appear to be related to an increase in the nucleation density of C-S-H in alkali hydroxide solutions. Examination under the SEM did not indicate significant difference in C-S-H morphology and composition in the presence of NaOH/KOH.

Department(s)

Materials Science and Engineering

Keywords and Phrases

Acceleration and deceleration; Alkali hydroxide; Alkalis (D); Dissolution mechanism; Experimental determination; Heat evolution; Heat release; Induction periods; Liquid phase compositions; Modeling platforms; Morphology and composition; Nucleation densities; Numerical predictions; Pore solution; Pore solution chemistry; Portlandite; Product formation; Salt addition; Simulations; Solid/liquid; Tricalcium silicate, Hydration; Potassium hydroxide, Calcium silicate

International Standard Serial Number (ISSN)

0008-8846

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2012 Elsevier Ltd, All rights reserved.

Publication Date

01 Nov 2012

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