Homra pozzolanic cement

The Pozzolanas can be divided into two main groups, natural and artificial. The natural Pozzolanas are mostly materials of volcanic origin and certain diatomoceous earths. The artificial Pozzolanas are mainly products obtained by the heat treatment of clays, shales, certain siliceous rocks, silica fumes, rice husk ash and pulverized fuel ash. Homra is a cheaper material than Portland cement with slow rate of hydration and low heat of hydration obtained from crushed parts of fired clay bricks, which is a source of active silica and alumina. The utilization of these industrial by-products is widely used because it reduces cost, energy and pollution. The aim of this work is to study the effect of substitution of Portland cement by 10, 20 and 30 wt \% homra on the physicochemical properties of cement pastes. The results revealed that the water of consistency increases with homra content, the initial and final setting times are elongated. The free Lime contents increase up to 7 days then decrease up to 90 days in homra blended cements whereas increase up to 90 days in OPC pastes. 20 wt \% is the optimum mix composition which gives suitable properties.