Protocols for investigating the reactivity of aggregates and alkali thresholds for ASR prevention

Nsiah-Baafi, E; Vessalas, K; Thomas, P; Sirivivatnanon, V

Protocols for investigating the reactivity of aggregates and alkali thresholds for ASR prevention

Nsiah-Baafi, E Vessalas, K Thomas, P

Sirivivatnanon, V

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Publisher:: LABORATÓRIO NACIONAL DE ENGENHARIA CIVIL (LNEC)
Publication Type:: Conference Proceeding
Citation:: Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete, 2021, 1, pp. 689-698
Issue Date:: 2021-01-01

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Field	Value	Language
dc.contributor.author	Nsiah-Baafi, E
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	Custodio, J
dc.contributor.editor	Serra, C
dc.date	2022-05-31
dc.date.accessioned	2021-05-27T07:17:04Z
dc.date.available	2021-05-27T07:17:04Z
dc.date.issued	2021-01-01
dc.identifier.citation	Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete, 2021, 1, pp. 689-698
dc.identifier.isbn	9789724923154
dc.identifier.uri	http://hdl.handle.net/10453/149270
dc.description.abstract	Alkali in concrete pore solution and reactive silica in aggregate are integral features required for alkalisilica reaction (ASR). When high amounts of alkali are present, expansive ASR gel forms that cause cracking of concrete. Thus, limits have been imposed, restricting allowable alkali contents for use in concrete. However, these limits are known to be generalised with a single limit specified for all aggregate types. This study investigates the reactivity potential and critical alkali threshold for individual aggregates and aggregate combinations, by increasing alkali content (0.60-1.25% Na2Oe) in concrete, varying exposure temperature (38-80°C) and extending test duration. A combination of RILEM recommended methods and modified versions of the standard accelerated mortar bar test (AMBT) and concrete prism test (CPT) expansion test methods have been used. The key findings of this study suggest that the potential exists for specifying a determined alkali threshold in concrete based on the reactivity classification of aggregates used, thus, allowing a relaxation of the current alkali limit for concrete. This approach permits greater flexibility in the potential safe use of reactive aggregates in concrete. Furthermore, this study shows that the determination of an aggregate’s reactivity and potential to ASR is not only highly dependent on its chemical composition and the alkali content in the concrete but also the test method, exposure temperature and test storage age used to assess changes in expansion.
dc.language	en
dc.publisher	LABORATÓRIO NACIONAL DE ENGENHARIA CIVIL (LNEC)
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.relation.ispartofseries	RNI 109
dc.rights	info:eu-repo/semantics/openAccess
dc.title	Protocols for investigating the reactivity of aggregates and alkali thresholds for ASR prevention
dc.type	Conference Proceeding
utslib.citation.volume	1
utslib.location.activity	Lisboa
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	open_access	*
pubs.consider-herdc	false
dc.date.updated	2021-05-27T07:17:03Z
pubs.finish-date	2022-06-02
pubs.place-of-publication	Lisboa
pubs.publication-status	Published
pubs.start-date	2022-05-31
pubs.volume	1
dc.location	Lisboa

Abstract:

Alkali in concrete pore solution and reactive silica in aggregate are integral features required for alkalisilica reaction (ASR). When high amounts of alkali are present, expansive ASR gel forms that cause cracking of concrete. Thus, limits have been imposed, restricting allowable alkali contents for use in concrete. However, these limits are known to be generalised with a single limit specified for all aggregate types. This study investigates the reactivity potential and critical alkali threshold for individual aggregates and aggregate combinations, by increasing alkali content (0.60-1.25% Na2Oe) in concrete, varying exposure temperature (38-80°C) and extending test duration. A combination of RILEM recommended methods and modified versions of the standard accelerated mortar bar test (AMBT) and concrete prism test (CPT) expansion test methods have been used. The key findings of this study suggest that the potential exists for specifying a determined alkali threshold in concrete based on the reactivity classification of aggregates used, thus, allowing a relaxation of the current alkali limit for concrete. This approach permits greater flexibility in the potential safe use of reactive aggregates in concrete. Furthermore, this study shows that the determination of an aggregate’s reactivity and potential to ASR is not only highly dependent on its chemical composition and the alkali content in the concrete but also the test method, exposure temperature and test storage age used to assess changes in expansion.

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http://hdl.handle.net/10453/149270