ABSTRACT
By denition, a pozzolan is “a siliceous or siliceous and aluminous material … that reacts chemically with calcium hydroxide (lime) to form compounds having cementitious properties.” In early civilizations, natural pozzolans were mixed together with lime to produce hydraulic cements, whereas today natural or articial pozzolans are usually used together with portland cement. The hydration of the calcium silicate compounds, C3S (or alite) and C2S (or belite), in portland cement produces abundant calcium hydroxide through the reactions represented by Equations 3.1 and 3.2 (see Table 3.1 for cement chemistry nomenclature).
