| Summary: | Volcanic rocks have been found to be potentially alkali-reactive in a number of countries, including Japan, Iceland and Turkey. To characterize the potential reactivity of the volcanic rocks used as aggregates for concrete in the Azores islands, an experimental program is being carried out which includes petrographic examination, chemical analysis and lab accelerated tests. The geochemical composition of the rocks of the Azores islands varies considerably. The rocks used as aggregates are mainly silica-undersaturated basalts and trachytes. The petrographic examination and the chemical analyses of the rocks confirmed that one of the five analysed samples contains free silica and another sample presents volcanic glass. The occurrence of microcrystalline quartz as a secondary product filling the interstices of the trachyte was confirmed by SEM/EDS. This paper presents the preliminary results obtained on the characterization of the first five samples of volcanic rocks from Azores regarding the potential reactivity to alkalis using different methods. 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 financial support of the FCT under the projects PTDC/CTM/65243/2006 and PDTC/ECM/115486/2009. 4 3 10p DM/NMM 2012 20 a 25 de maio
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