The study of the Azorean volcanic aggregates from the point of view of alkali silica reaction

Abstract

Volcanic rocks are the main source of concrete aggregates in Azores archipelago. In order to understand the reactivity of these rocks in this Portuguese territory, a study was implemented in the past three years to evaluate the potential alkali-reactivity of thirteen aggregates collected in these islands. For this study, a petrographic characterization and a chemical analysis were made on the rock samples and expansion tests were performed on the aggregates. The petrographic and the chemical analyses of the rocks confirmed that one of the samples contains free silica and three samples present interstitial volcanic glass. Microcrystalline quartz was confirmed by SEM/EDS as a secondary product filling the interstices of trachyte sample. The expansion tests show that the trachyte is the only aggregate with potential alkali-reactivity in the accelerated mortar-bar test. This paper presents the main results of eleven aggregates regarding the potential alkalireactivity of the volcanic rocks from this archipelago.