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Portland Pozzolana Cement (PPC)
The Portland Pozzolana Cement is a kind of Blended Cement which is produced by either intergrinding of OPC clinker along with gypsum and pozzolanic materials in certain proportions or grinding the OPC clinker, gypsum and Pozzolanic materials separately and thoroughly blending them in certain proportions.
Pozzolana is a natural or artificial material containing silica in a reactive form. It may be further discussed as siliceous or siliceous and aluminous material which in itself possesses little, or no cementitious properties but will in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties. It is essential that pozzolana be in a finely divided state as it is only then that silica can combine with calcium hydroxide (liberated by the hydrating Portland Cement) in the presence of water to form stable calcium silicates which have cementitious properties. The pozzolanic materials commonly used are:
- Volcanic ash
- Calcined clay
- Fly ash
- lica fumes
The Indian standards for Portland Pozzolana Cement have been issued in two parts based on the type of pozzolanic materials to be used in manufacturing of Portland Pozzolana Cement as given below:
- IS 1489 (Part 1) 1991, Portland Pozzolana Cement - specification (fly ash based)
- IS 1489 (Part 2) 1991, Portland Pozzolana Cement - specification (Calcined clay based)
The quality of flyash or calcined clay to be used in manufacturing of PPC is also specified by BIS in the following standards:
- IS 3812 1981 - specification for flyash as pozzolana and admixture
- IS 1344 1981 - specification for calcined clay pozzolana
The Portland Pozzolana Cement produces less heat of hydration and offers greater resistance to the attack of aggressive waters than normal Portland Cement. Moreover it reduces the leaching of calcium hydroxide liberated during the setting and hydration of cement.
The Portland Pozzolana Cement is ideally suited for the following construction.
- Hydraulic structures
- Mass concreting works
- Marine structures
- Masonry mortars and plastering
- Under aggressive conditions.
- All other application where OPC is used.
Physical Characteristics of PPC (BIS Requirement)
Is Code Finene SS (sq.m/k g Min) Soundness by Setting Time Compressive Strength
Lechatlier (mm)max Auto clave Max (%) Initial (mts) min Final (mts) Max 1 day Min Mpa 3 day Min Mpa 7 day Min Mpa 28 day Min Mpa
IS (1489- 1991) part 1 300 10 0.8 30 600 NS 16 22 33
Chemical Characteristics of PPC (BIS Requirement)
Is Code Lime Saturation Factor Alumina Ration Min Insoluble Residue (%) Max MgO (%) Max Sulphuric Anhydride Loss ignition (%) Max
IS (1489-1991) Part-I (flyash based) Not specified Not specified X+4(100- x)/4 6 3% Max 5
X - Declared % of Flyash.
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