Portland Pozzolana Cement

• The history of pozzolanic material goes back to Roman’s time. The descriptions and details of pozzolanic material will be dealt separately under the chapter ‘Admixtures’.
• Portland Pozzolana cement (PPC) is manufactured by the intergrinding of OPC clinker with 10 to 25 per cent of pozzolanic material (as per the latest amendment, it is 15 to 35%).
• A pozzolanic material is essentially a silicious or aluminous material which while in itself possessing no cementitious properties, which will, in finely divided form and in the presence of water, react with calcium hydroxide, liberated in the hydration process, at ordinary temperature, to form compounds possessing cementitious properties.
• The pozzolanic materials generally used for manufacture of PPC are calcined clay or fly ash.
• The pozzolanic action is shown below:
  
  Calcium hydroxide + Pozzolana + water ----> C – S – H (gel)
• Portland pozzolana cement produces less heat of hydration and offers greater resistance to the attack of aggressive waters than ordinary Portland cement. Moreover, it reduces the leaching of calcium hydroxide when used in hydraulic structures. It is particularly useful in marine and hydraulic construction and other mass concrete constructions.

• For hydraulic structures;
• For mass concrete structures like dam, bridge piers and thick foundation;
• For marine structures;
• For sewers and sewage disposal works.