Li, Q, Li, X, Yang, K et al. (4 more authors) (2021) The long-term failure mechanisms of alkali-activated slag mortar exposed to wet-dry cycles of sodium sulphate. Cement and Concrete Composites, 116. 103893. ISSN 0958-9465
Abstract
This study investigates the long-term (570 days) performance of alkali-activated slag (AAS) mortar exposed to combined wet-dry cycles and sodium sulphate solutions (i.e. 5 wt% and 10 wt%). Physical and mechanical characteristics of AAS mortars (i.e. visual appearance, compressive/flexural strength, mass change, capillary porosity, water sorptivity) as well as mineralogical and chemical parameters were determined using XRD, FTIR, DSC and BSE. Findings were compared to Portland cement (PC) and high sulphate resistant (HSR) samples. Results indicate that AAS mortars perform better than PC and HSR samples with minimal changes to compressive strength at 570 days (1.7% increasement). The main failure mode for AAS mortar was external spalling, which could be due to the crystallisation/dissolving pressure of sodium sulphate. Moreover, the results indicate key differences in the deterioration mechanism of AAS. Unreacted slag, exposed during sodium sulphate attack under wet-dry cycles, can continue to react in sodium sulphate to form silicon-rich gels. The formation of highly siliceous gel regions has beneficial impacts, such as the increase in flexural strength. While no calcium sulphate phases were detected via XRD and FTIR after 570 days of exposure, it is evident that the molecular changes in the microstructure reveal depolymerisation and enhanced formation of Si–O phases after long-term sodium sulphate exposure. These results are important to understand the long-term degradation mechanisms of AAS materials exposed to sodium sulphate under wet-dry cycles.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2020 Published by Elsevier Ltd. All rights reserved. This is an author produced version of an article published in Cement and Concrete Composites. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Alkali-activated slag material; Deterioration; Crystallisation and dissolving stress; Sulphate attack; Wetting and drying cycles |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Civil Engineering (Leeds) > Institute for Resilient Infrastructure (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 19 May 2021 11:22 |
Last Modified: | 09 Dec 2021 01:39 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.cemconcomp.2020.103893 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:174209 |
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