Civil Engineering Today

  Pozzolana The term pozzolana is derived from Pozzuoli , a town in Italy on the Bay of Naples near Mount Vesuvious . The sand (volcanic dust) around this town when mixed with hydrated lime was found to possess hydraulic properties . Pozzolana may be defined as a siliceous material which  itself possessing no cementitious properties, either processed or unprocessed and in finely divided form, reacts in the presence of water with lime at normal temperatures to form compounds of low solubility having cementitious properties. Pozzolanas may be natural or artificial , fly ash being the best known in the latter  category. Before the advent  of cement these were used with lime to make concrete.   THE ACTIVITY OF P0ZZOLANA - When mixed with ordinary Portland cement the silica of the pozzolana combines with the free lime released during the hydration of cement. This action is called pozzolanic action . The pozzolanic activity is due to the presence of finely divid...