Difference between Ordinary Portland Cement (OPC) and Portland Pozzolana Cement(PPC) Portland Pozzolana Cement is a variation of Ordinary Portland Cement. Pozzolana materials namely fly ash, volcanic ash, are added to the OPC so that it becomes PPC. Pozzolana materials are added to the cement in the ratio of 15% to 35% by weight. Pozzolana Cement uses natural and industrial waste like fly ash thus reducing the environmental pollution.