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Materials 2016, 9(6), 462; doi:10.3390/ma9060462

Some Issues of Shrinkage-Reducing Admixtures Application in Alkali-Activated Slag Systems

Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Brno 612 00, Czech Republic
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Academic Editor: Claudio Ferone
Received: 9 May 2016 / Revised: 31 May 2016 / Accepted: 6 June 2016 / Published: 10 June 2016
(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)
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Abstract

Significant drying shrinkage is one of the main limitations for the wider utilization of alkali-activated slag (AAS). Few previous works revealed that it is possible to reduce AAS drying shrinkage by the use of shrinkage-reducing admixtures (SRAs). However, these studies were mainly focused on SRA based on polypropylene glycol, while as it is shown in this paper, the behavior of SRA based on 2-methyl-2,4-pentanediol can be significantly different. While 0.25% and 0.50% had only a minor effect on the AAS properties, 1.0% of this SRA reduced the drying shrinkage of waterglass-activated slag mortar by more than 80%, but it greatly reduced early strengths simultaneously. This feature was further studied by isothermal calorimetry, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Calorimetric experiments showed that 1% of SRA modified the second peak of the pre-induction period and delayed the maximum of the main hydration peak by several days, which corresponds well with observed strength development as well as with the MIP and SEM results. These observations proved the certain incompatibility of SRA with the studied AAS system, because the drying shrinkage reduction was induced by the strong retardation of hydration, resulting in a coarsening of the pore structure rather than the proper function of the SRA. View Full-Text
Keywords: alkali activated slag; shrinkage reducing admixture; shrinkage; hydration; microstructure; retardation alkali activated slag; shrinkage reducing admixture; shrinkage; hydration; microstructure; retardation
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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Bílek, V.; Kalina, L.; Novotný, R.; Tkacz, J.; Pařízek, L. Some Issues of Shrinkage-Reducing Admixtures Application in Alkali-Activated Slag Systems. Materials 2016, 9, 462.

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