The evaluation of reaction potential of different aggregates based on petrographic studies and comparison with chemical tests.

The durability of concrete is affected by various factors including its ingredients, workmanship, environment, working life, and so on. The alkali reaction within the concrete can shorten its lifespan due to the expansive pressure build up and cracking caused by the deleterious action of alkali reaction by-products. The alkali reaction is a gradual reaction that can happen between the alkaline pore solution of the concrete and various types of aggregates. Understanding the behavior of the aggregate, as the main reactive component, is thus essential in understanding of the reaction mechanism, reducing the alkali reaction potential or even preventing it. Not all aggregates are susceptible to alkali reaction. Therefore, detecting susceptible aggregates and selecting the ones with low levels of reactive materials, can eventually help to minimize and mitigate alkali reaction problems. The aim of this research was to assess the susceptibility of four commonly used aggregates in constructing projects: Granite, Rhyodacite, Limestone and Dolomite. The study was performed under accelerated conditions in accordance with the ASTM test method C1260 and ambient condition (room temperature).specimens were analyzed using Scanning Electron Microscopy (SEM),X-ray Diffraction (XRD) and Light Microscopy. Limestone and Rhyodacite aggregates, were found to be susceptible to expansion reaction.