Pozzolanic reactivity of low grade kaolinitic clays: Influence of mineralogical composition

The influence of chemical and mineralogical composition of five Cuban clays in the pozzolanic reactivity of its calcination products is studied in this research. Raw materials were chemically and mineralogically characterized by XRF, XRD and TGA. Pozzolanic reactivity of 800 °C calcination products was evaluated by heat released in chemically modified lime-pozzolan pastes, and by compressive strength in mortars with a 30% substitution of OPC by calcined clays. Preliminary results shown that pozzolanic reactivity of clays calcined at temperatures that guarantees a complete dehydroxylation of the raw materials could be qualitatively assessed by its relative positions along the diagonal trend in an Al₂O₃–SiO₂–OH⁻ ternary plot, where pozzolanic reactivity is related to the percent of structural hydroxyl groups and the percent of Al₂O₃ in the raw material. Conducted pozzolanic reactivity test highlight the potential of kaolinite rich red clay soils as source for the obtaining of highly reactive pozzolanic materials.