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Simple Model for Alkali Leaching from Geopolymers: Effects of Raw Materials and Acetic Acid Concentration on Apparent Diffusion Coefficient

Ukrainczyk, Neven (2022):
Simple Model for Alkali Leaching from Geopolymers: Effects of Raw Materials and Acetic Acid Concentration on Apparent Diffusion Coefficient. (Publisher's Version)
In: Materials, 14 (6), MDPI, e-ISSN 1996-1944,
DOI: 10.26083/tuprints-00019598,
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Item Type: Article
Origin: Secondary publication DeepGreen
Status: Publisher's Version
Title: Simple Model for Alkali Leaching from Geopolymers: Effects of Raw Materials and Acetic Acid Concentration on Apparent Diffusion Coefficient
Language: English
Abstract:

This paper investigates alkali leaching from geopolymers under various concentrations of acetic acid solutions. The effects of the raw metakaolin purity as well as fly ash-based geopolymer mortars and pastes are considered. A new methodology for (acetic) acid attack is proposed, adapting standard approaches, where the concentration of the leached alkali in the exposure solution is measured over time. The applicability of a simple diffusion-based mathematical model to determine the apparent diffusion coefficient (Dapp) for geopolymer pastes and mortars was validated. At the end of the paste tests, microstructural alterations of the specimens’ cross-sections were analyzed microscopically, revealing occurrence of degradation across the outermost surface parts and, especially under acid attack, the formation of long cracks that connect the surface with the intact inner zone. Drastically different Dapp are discussed in terms of the differences in the mix designs, principally resulting in different alkali-binding capacities of the geopolymers, while the acid promoted dissolution and increased porosity. As a result of this interpretation, it was concluded that Dapp is governed mainly by the chemistry of the alkali release from the gel, as it overruled the effects of porosity and cracks.

Journal or Publication Title: Materials
Volume of the journal: 14
Issue Number: 6
Publisher: MDPI
Collation: 20 Seiten
Uncontrolled Keywords: geopolymers, metakaolin purity, alkali leaching, acetic acid attack, mathematical modeling, apparent diffusion coefficient
Classification DDC: 600 Technik, Medizin, angewandte Wissenschaften > 600 Technik
600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften
Divisions: 13 Department of Civil and Environmental Engineering Sciences > Institute of Construction and Building Materials
Date Deposited: 02 Feb 2022 13:29
Last Modified: 02 May 2022 12:07
DOI: 10.26083/tuprints-00019598
Corresponding Links:
URN: urn:nbn:de:tuda-tuprints-195985
SWORD Depositor: Deep Green
URI: https://tuprints.ulb.tu-darmstadt.de/id/eprint/19598
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