New selective dissolution process to quantify reaction extent and product stability in metakaolin-based geopolymers

Longhi, Marlon and Walkley, Brant and Rodriguez, Erich D and Kirchheim, Ana P and Zhang, Zuhua and Wang, Hao (2019) New selective dissolution process to quantify reaction extent and product stability in metakaolin-based geopolymers. Composites Part B: Engineering, 176 (1). ISSN 1359-8368

Abstract

A selective dissolution process is developed that can quantify the amount of soluble material, geopolymer gel and remnant unreacted precursor in metakaolin-based geopolymer systems and determine the nanostructural features of the raw materials and geopolymer gel components. The susceptibility of alkalis leachability from the alkaline aluminosilicate hydrate-type gel (N-A-S-H) produced during the geopolymerization is not fully understood. This phenomenon led to deleterious processes from a microstructural, aesthetic and performance point of view. Geopolymers were synthesised using different contents and types of alkalis (M/Al = 0.50–0.83, where M represents Na or K), different contents of soluble silica in the activator (expressed as SiO2/M2O ratio of 1.0, 0.5 and 0.0), and curing temperatures (25 and 50 °C). The selective dissolution process is based on neutral dissolution at pH 7 to extract the soluble materials and acid dissolution using a strong acid at pH 0 to dissolve the geopolymer gel, which provides for the first time a method to quantify the (i) soluble material, (ii) geopolymer gel and (iii) unreacted material in geopolymers. The soluble material provides a reliable indication of the materials that can be removed from the geopolymers in a neutral pH environment and hence the potential for leaching and efflorescence, which is useful for durability prediction and service life. Quantification of remnant unreacted metakaolin determines the reactivity of the precursor and assesses the suitability of different synthesis conditions for varied applications. This work therefore provides a novel and widely applicable approach to determine the susceptibility of geopolymer materials to leaching.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Date Deposited: 20 Jan 2020 03:53
Last Modified: 07 Feb 2020 01:29
Uncontrolled Keywords: Alkali activation; Geopolymer; Aluminosilicate; Leaching
Fields of Research : 09 Engineering > 0905 Civil Engineering > 090503 Construction Materials
Identification Number or DOI: 10.1016/j.compositesb.2019.107172
URI: http://eprints.usq.edu.au/id/eprint/37682

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