Assessment of potential alkali-silica reactivity of aggregates for concrete

The detection of concrete structures affected by Alkali-Silica Reaction (ASR) has increased dramatically over the past couple of decades in Portugal. Due to the complexity and multiplicity of factors involved in ASR together with the variability of the materials used, no International or European standards exist for assessing the aggregates potential alkali-reactivity, and each country must rely on national regulations or specifications. Because of that, in Portugal, LNEC Specification E 415 was prepared in 1993 and LNEC Specification E 461 was introduced in 2004 and revised in 2007. However, due to the scientific developments occurred since then, new revised versions were prepared and will soon be published. Although, LNEC Specifications provide guidance on the identification of potentially alkali-silica reactive aggregates, there are still some knowledge gaps on how to reliably assess the potential reactivity of some minerals present in granites and similar rocks, which are the type of aggregate most used in large concrete structures in Portugal. Therefore, to contribute to the current ongoing discussion on the role of the main components of these rocks on ASR development, this paper presents the methodology that was applied in the evaluation of concrete granitic aggregates used in recently built hydroelectric projects as well as in a dam constructed abroad several decades ago, and in which the deleterious development of ASR was detected 15 years after construction.