In this investigation hydration and microstructural characteristics of pozzolanic cement pastes were studied. The cement used consists of ordinary Portland cement (OPC) and artificial pozzolana made of calcined mixed layer clay. OPC was partially replaced by 0, 10, 20 and 30% artificial pozzolana, by weight. The pastes were prepared using the standard water of consistency of 0.255, 0.258, 0.263 and 0.275 for 0, 10, 20 and 30% pozzolana, respectively. The changes in the electrical conductivity were reported during setting and hardening after gauging with water. The phase composition and microstructure of pozzolanic cement pastes were investigated by differential thermal analysis and scanning electron microscopy. The results of this investigation showed that, the thermally activated clay reduces the initial and final setting times of the pastes. It also improved the resulting microstructure of the formed hydrates by consumption of Ca(OH)_2 and recrystalization of CSH phases.
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