Journal of Advanced Concrete Technology
Scientific paper
Effect of Alkalis on Cementitious Materials:Understanding the Relationship between Composition, Structure, and Volume Change Mechanism
Hailong YeAleksandra Radlińska
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Volume 15 (2017) Issue 4 Pages 165-177

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Abstract

Previous studies demonstrated that alkalis can considerably affect the volumetric properties of hardened cementitious binders, including shrinkage, creep, and micro-cracking. The objective of this paper is to reexamine the effect of alkalis on the composition, nanostructure, phase stability, and morphology of calcium-silicate-hydrate (C-S-H) in cementitious materials, and to further propose a conceptual model bridging the C-S-H characters with its volume change mechanisms in alkali-enriched systems. The proposed microstructural model is an extension of the colloidal model of C-S-H considering the effect of alkalis. It is suggested that the presence of alkalis makes C-S-H more thermodynamically unstable and structurally disrupted, and easier to reorganize and redistribute upon drying-induced internal stresses or external loading. In addition, new experimental results regarding the influence of lithium on shrinkage and micro-cracking of alkali-activated blast-furnace slag are discussed. It shows that lithium addition can dramatically improve the cracking resistance and volumetric stability of alkali-activated slag.

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© 2017 by Japan Concrete Institute
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