An overview on the activation of reactivity of natural pozzolans

Natural pozzolan is one of the oldest construction materials. Lime-pozzolan cements have been used for several thousands of years and have an excellen t reputation for their durability. Pozzolans are being widely used as a cem ent replacement in Portland cement concrete. The use of pozzolans has the a dvantage of lower costs and better durability, but the disadvantage of a lo nger setting time and a slower early strength development. Different techni ques have been tried to increase the reactivity of natural pozzolans to ove rcome these disadvantages. This paper has reviewed various methods used to activate the pozzolanic activity of natural pozzolans. All activation metho ds can be classified into three catalogues: thermal, mechanical, and chemic al activation. A comparison based on strength-cost relationship indicates t hat the chemical activation method is the most effective and cheapest one.