Pozzolana

Pozzolana is a material of interest for civil engineers. It is used in building construction. It consists of amorphous silica or a mixture of amorphous silica and alumina. Pozzolana when mixed with calcium hydroxide at ambient temperature in the presence of moisture, becomes a cementitius material. The mixture is called lime-pozzolana cement. Pozzolana can be derived from powdered burnt clay, fly ash or rice husk ash. Amount of sand should be minimized while burning clay since sand does not react with lime. Fly ash as pozzolana is usually obtained from thermal power stations where pulverized coal is used as the fuel. Fly ash is nothing but the very fine particles of burnt coal which contain significant amounts of amorphous silica and alumina. Rice husk ash is a natural source of silica. There are many methods of production of lime-pozzolana cement. They are wet grinding using lime-surkhi mortar, dry blending of lime and pozzolana and wet blending of lime and pozzolana.