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Materials 2016, 9(7), 605; doi:10.3390/ma9070605

Hydration of Hybrid Alkaline Cement Containing a Very Large Proportion of Fly Ash: A Descriptive Model

Cement and Recycling Materials Department, Eduardo Torroja Institute (IETcc-CSIC), Madrid 28033, Spain
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Academic Editor: Arie van Riessen
Received: 24 May 2016 / Revised: 8 July 2016 / Accepted: 18 July 2016 / Published: 22 July 2016
(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)
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Abstract

In hybrid alkaline fly ash cements, a new generation of binders, hydration, is characterized by features found in both ordinary portland cement (OPC) hydration and the alkali activation of fly ash (AAFA). Hybrid alkaline fly ash cements typically have a high fly ash (70 wt % to 80 wt %) and low clinker (20 wt % to 30 wt %) content. The clinker component favors curing at ambient temperature. A hydration mechanism is proposed based on the authors’ research on these hybrid binders over the last five years. The mechanisms for OPC hydration and FA alkaline activation are summarized by way of reference. In hybrid systems, fly ash activity is visible at very early ages, when two types of gel are formed: C–S–H from the OPC and N–A–S–H from the fly ash. In their mutual presence, these gels tend to evolve, respectively, into C–A–S–H and (N,C)–A–S–H. The use of activators with different degrees of alkalinity has a direct impact on reaction kinetics but does not modify the main final products, a mixture of C–A–S–H and (N,C)–A–S–H gels. The proportion of each gel in the mix does, however, depend on the alkalinity generated in the medium. View Full-Text
Keywords: hybrid alkaline cement; alkaline activation; fly ash; geopolymer; descriptive hydration model; gel microstructure hybrid alkaline cement; alkaline activation; fly ash; geopolymer; descriptive hydration model; gel microstructure
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Garcia-Lodeiro, I.; Donatello, S.; Fernández-Jiménez, A.; Palomo, Á. Hydration of Hybrid Alkaline Cement Containing a Very Large Proportion of Fly Ash: A Descriptive Model. Materials 2016, 9, 605.

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