This practice describes approaches for identifying potentially deleteriously reactive aggregates and selecting appropriate preventive measures to minimize the risk of expansion when such aggregates are used in concrete. Both alkali-silica reactive and alkali-carbonate reactive aggregates are covered. Preventive measures for alkali-silica reactive aggregates include avoiding the reactive aggregate, limiting the alkali content of the concrete, using blended cement, using supplementary cementitious materials, using lithium nitrate as an admixture, or a combination of these measures. Preventive measures for alkali-carbonate reactive rocks are limited to avoiding the reactive aggregate.