The Portland pozzolana cement is manufactured by mixing ordinary portland cement with 10 to 25 percent of the pozzolanic material.
The pozzolanic material may not posses cementitious property but it is a material which essentially contains silicious or aluminous material.
The pozzolanic material is in finely divided form and the material mainly used for making portland pozzolana cement is fly ash and calcined clay.
The calcined clay has low carbon content and it can reduce carbon content to 30 percent when comparing to the production of ordinary Portland cement. It can be used fro pozzolanic material for making PPC.
Properties of Portland Pozzolana Cement.
The very first property it liberates only a small amount of heat and it can offer more resistance to attack of aggressive water.PPC can reduce leaching of calcium hydroxide.
However fly ash and calcined clay are used for changing the property of cement, they cant impose any changes to the strength of the hardened concrete. That is strength will be similar to ordinary Portland cement concrete as expected.
What are the advantages of PPC?
- PPC can reduce microcracks in the transition zone and it improves pore size distribution.
- Since PPC is finer than OPC, the permeability can be reduced.
- Since the fly ash has lesser density and more finer.PPC can give more volume of mortar than OPC.
- The long-term strength of PPC is greater than of OPC.
- PPC is more economical because the costly clinker can be replaced with fly ash or calcined clay. Fly ash is a byproduct in coal combustion process.
- The heat liberated during the heat of hydration will be lesser than that of OPC.
Some disadvantages of PPC is, the initial strength slightly lesser than that of OPC and the reduction in alkalinity causes loss of resistance against corrosion in steel reinforcement.
Uses of Portland Pozzolana cement
- Mass concrete structures because of less liberation of heat. ( Bridge piers, dams )
- For hydraulic structures
- Sewers and Sewage
- For marine structures
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