Dissolution behaviour of SCMs in alkaline environment and mechanisms behind ASR mitigation

Tapas, MJ; Vessalas, K; Thomas, P; Sirivivatnanon, V

Dissolution behaviour of SCMs in alkaline environment and mechanisms behind ASR mitigation

Tapas, MJ Vessalas, K Thomas, P

Sirivivatnanon, V

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Publisher:: LABORATÓRIO NACIONAL DE ENGENHARIA CIVIL, I. P.
Publication Type:: Conference Proceeding
Citation:: Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete, 2021, 1, pp. 423-430
Issue Date:: 2021-01-01

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Field	Value	Language
dc.contributor.author	Tapas, MJ
dc.contributor.author	Vessalas, K
dc.contributor.author	Thomas, P https://orcid.org/0000-0001-6962-2121
dc.contributor.author	Sirivivatnanon, V
dc.contributor.editor	Lopes Batista, A
dc.contributor.editor	Santos Silva, A
dc.contributor.editor	Fernandes, I
dc.contributor.editor	Oliveira Santos, L
dc.contributor.editor	Custódio, J
dc.contributor.editor	Serra, C
dc.date	2022-05-31
dc.date.accessioned	2021-05-27T07:43:33Z
dc.date.available	2021-05-27T07:43:33Z
dc.date.issued	2021-01-01
dc.identifier.citation	Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete, 2021, 1, pp. 423-430
dc.identifier.isbn	9789724923154
dc.identifier.uri	http://hdl.handle.net/10453/149274
dc.description.abstract	Fly ash and slag are supplementary cementitious materials (SCMs) commonly used to mitigate alkali-silica reaction (ASR). However, future supply of these SCMs is at risk due to a global push to reduce coal-fired energy production and increased steel recycling. Thus, an immediate need to identify alternative SCMs is critical. In order to establish the efficacy of an SCM in its ability to mitigate ASR, an understanding of the chemical processes involved in ASR mitigation is required. This study aims to better understand the mechanisms behind ASR mitigation by comparing the amount of silicon (Si) and aluminium (Al) released by SCMs under AMBT conditions, investigating the interaction of the dissolved SCM species in the system (i.e. formation of reaction products) and how these correlate to explain the differences in SCM dosage requirements for effective mitigation. Results show that the ability of SCMs to release Si is as follows: SF>MK>FA>SL which correlates well with the dosage required to mitigate ASR. This indicates that the efficacy of SCMs in mitigating ASR is primarily due to their ability to release Si in solution. Formation of sodium aluminium silicate hydrate (N-A-S-H) in fly ash and metakaolin and formation of calcium aluminium silicate hydrate (C-A-S-H) in slag post alkali immersion were also observed. This indicates the ability of aluminium to bind silicon and precipate alkali in the process (effectively reducing solution alkali concentration) and highlights its beneficial effect on ASR mitigation. Further, in systems saturated with calcium, Ca is bound instead of Na suggesting the occurence of competitive reactions and subsquent alkali recycling. Calcium, therefore, does not appear to have a beneficial effect on ASR mitigation.
dc.language	en
dc.publisher	LABORATÓRIO NACIONAL DE ENGENHARIA CIVIL, I. P.
dc.relation	http://purl.org/au-research/grants/arc/IH150100006
dc.relation.ispartof	Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete
dc.relation.ispartof	16th International Conference on Alkali-Aggregate Reaction in Concrete
dc.rights	info:eu-repo/semantics/closedAccess
dc.title	Dissolution behaviour of SCMs in alkaline environment and mechanisms behind ASR mitigation
dc.type	Conference Proceeding
utslib.citation.volume	1
utslib.location.activity	Lisbon
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - CBI - Centre for Built Infrastructure
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences
utslib.copyright.status	closed_access	*
pubs.consider-herdc	false
dc.date.updated	2021-05-27T07:43:32Z
pubs.finish-date	2022-06-02
pubs.place-of-publication	Lisbon
pubs.publication-status	Published
pubs.start-date	2022-05-31
pubs.volume	1
dc.location	Lisbon

Abstract:

Fly ash and slag are supplementary cementitious materials (SCMs) commonly used to mitigate alkali-silica reaction (ASR). However, future supply of these SCMs is at risk due to a global push to reduce coal-fired energy production and increased steel recycling. Thus, an immediate need to identify alternative SCMs is critical. In order to establish the efficacy of an SCM in its ability to mitigate ASR, an understanding of the chemical processes involved in ASR mitigation is required. This study aims to better understand the mechanisms behind ASR mitigation by comparing the amount of silicon (Si) and aluminium (Al) released by SCMs under AMBT conditions, investigating the interaction of the dissolved SCM species in the system (i.e. formation of reaction products) and how these correlate to explain the differences in SCM dosage requirements for effective mitigation. Results show that the ability of SCMs to release Si is as follows: SF>MK>FA>SL which correlates well with the dosage required to mitigate ASR. This indicates that the efficacy of SCMs in mitigating ASR is primarily due to their ability to release Si in solution. Formation of sodium aluminium silicate hydrate (N-A-S-H) in fly ash and metakaolin and formation of calcium aluminium silicate hydrate (C-A-S-H) in slag post alkali immersion were also observed. This indicates the ability of aluminium to bind silicon and precipate alkali in the process (effectively reducing solution alkali concentration) and highlights its beneficial effect on ASR mitigation. Further, in systems saturated with calcium, Ca is bound instead of Na suggesting the occurence of competitive reactions and subsquent alkali recycling. Calcium, therefore, does not appear to have a beneficial effect on ASR mitigation.

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http://hdl.handle.net/10453/149274