Alkali-aggregate reaction

Alkali-aggregate reaction in concrete is the name given to a group of reactions leading to expansion caused by a chemical reaction between the alkalis contained in the cement paste and certain reactive forms of (usually silica containing) minerals in the aggregates, see Figure 4. The alkalis in the pore solution are derived from the hydration of the cement but may be augmented by alkalis in some aggregates or alkaline salts from the environment [5].