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dc.contributor.authorMedeiros, S.pt_BR
dc.contributor.authorRamos, V.pt_BR
dc.contributor.authorFernandes, I.pt_BR
dc.contributor.authorNunes, J. C.pt_BR
dc.contributor.authorFournier, B.pt_BR
dc.contributor.authorSantos Silva, A.pt_BR
dc.contributor.authorSoares, D.pt_BR
dc.description.abstractAlkali-silica reaction (ASR) is a type of deterioration that has been causing serious expansion, cracking and durability/operational issues in concrete structures worldwide. The presence of sufficient moisture, high alkali content in the cement paste and reactive forms of silica in the aggregates are the required conditions for this reaction to occur. Reactive aggregates of volcanic nature have been reported in different countries such as Japan, Iceland and Turkey, among others. The presence of silica minerals and SiO2-rich volcanic glass is regarded as the main cause for the reactivity of volcanic rocks. In Portugal, volcanic aggregates are mainly present in Azores and Madeira Archipelagos and, for several years, there was no information regarding the potential alkali-reactivity of these rocks. Since the beginning of this decade some data was obtained by the work of Medeiros (2011) and Ramos (2013) and by the national research projects ReAVA, (Characterization of potential reactivity of the volcanic aggregates from the Azores Archipelago: implications on the durability of concrete structures) and IMPROVE (Improvement of performance of aggregates in the inhibition of alkali-aggregate reactions in concrete), respectively. In order to investigate the potential alkali-reactivity of aggregates from both archipelagos, a total of sixteen aggregates were examined under the optical microscope and, some of them, also under the Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy. A set of geochemical analyses and laboratory expansion tests were also performed on those volcanic aggregates. The main results showed that the presence of volcanic glass is rare in both archipelagos and that the samples of Madeira Archipelago contain clay minerals (mainly from scoria/tuff formations inter-layered with the lava flows), which can play a role in concrete expansion. The results of the laboratory tests showed that one of the samples performed as potentially reactive in the accelerated mortar-bar test (ASTM C 1260) and that the majority of the Azores samples started to show some expansion just after one year of testing in the concrete prism test (CPT) at 38ºC.pt_BR
dc.publisherIOP Publishing Ltdpt_BR
dc.subjectVolcanic aggregatespt_BR
dc.titleVolcanic aggregates from Azores and Madeira archipelagos (Portugal): an overview regarding the alkali sílica reactionspt_BR
dc.description.commentsThe authors would like to acknowledge the financial support of Azorean Regional Government through the Regional Fund for Science (FRC - Fundo Regional para a Ciência) for the project ReAVA (ref.M5.2.2/I/05/2011) and LNEC, ICT (University of Porto) and FCT for the financial support of Project IMPROVE (Ref: PTDC/ECM/115486/2009) and of the Strategic Project PESTOE/ CTE/UI0039/2014. The analyses by SEM/EDS were performed at CEMUP which equipment was funded by the projects REEQ/1062/CTM/2005 and REDE/1512/RME/2005 of Portuguese Foundation for Science and Technology (FCT). The authors also acknowledge the LNEC support through the REImprove project and the contribution of construction companies. The first author also acknowledges the PhD scholarship granted by the FRCT (refª: M3.1.a/F/006/2015). V. Ramos is grateful to FCT towards the financial support of her PhD studies (Ref: SFRH/BD/47893/2008) and acknowledges the funding by COMPETE 2020 through the ICT project (UID/GEO/04683/2013) with POCI-01-0145 reference - FEDER-007690. This publication is also supported by FCT- project UID/GEO/50019/2013 – IDL.pt_BR
dc.identifier.localPrague, Czech Republicpt_BR
dc.description.magazineIOP Conference Series: Earth and Environmental Sciencept_BR
dc.identifier.conftitleWorld Multidisciplinary Earth Sciences Symposium (WMESS 2017)pt_BR
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