Petrographic identification of reactive minerals in domestic aggregates and their classification according to RILEM and ASTM recommendations

Considering the long-time durability of concrete in road infrastructure it is important to control the threat of expansive reaction between sodium and potassium hydroxides in the pore solution and the reactive minerals present in the aggregate. Petrographic analysis is the basis for the qualification of aggregates to appropriate classes of reactivity according to ASTM C1778 and RILEM recommendations. The paper presents the results of petrographic analyses of thin sections made from twenty different domestic aggregates. The tested crushed aggregates were obtained from bedrock and glacial deposits. The evaluation of the mineral composition of aggregates included identification of deleterious components and determination of the content of reactive forms of silica. This enabled preliminary classification of aggregate in one of the three classes of reactivity according to RILEM. Obtained results provide an initial assessment of potential reactivity of aggregates and can assist in making decisions to undertake further accelerated or long-term laboratory testing or to modify the concrete mix design.