Effect of Silica Dissolution on the Mechanical Characteristics of Alkali-Reactive Aggregates

Abstract

High pH nature of concrete microstructure can lead to chemical interaction between reactive silica in aggregate and alkali species in pore solution. As a result, alkali silica gel is rendered which can cause distress in hardened concrete. However, the consequence of silica dissolution is not only the gel formation and damage in cement paste, but also significant weakening of the reactive aggregate itself. In this study, three highly reactive, well-documented concrete aggregates were investigated. The aim was to characterize the micromechanical and -morphological alterations of the aggregates under aggressive alkaline solution by means of microscopy and nano-indentation techniques. It was found that silica dissolution alters micromorphology of the reactive aggregates and reduces elastic modulus and hardness values significantly.