TYPES OF CEMENT
ORDINARY PORTLAND CEMENT (PC)
It is popularly known as gray cement, has 95 per cent clinker and 5 per cent Gypsum and other materials, 3 grades of Cement, are produced by ICL.
- 53 Grade Cement:
53 Grade cement, is a higher strength cement to meet the needs of the consumer for higher Strength concrete. As per BIS requirements, the minimum 28 days compressive strength of 53 Grade cement, should not be less than 53MPa. For certain specialized works, such as pre stressed concrete and certain items of precast concrete requiring consistently high strength concrete, the use of 53 Grade cement, is found very useful. In concrete mix design, for concrete M-20 and Above grades, a saving of 8 to 10% of cement may be achieved with the use of 53 grade cement. It is mostly used in paving blocks, tiles, building blocks, runways, concrete roads, bridges and Similar heavy constructions.
- 43 Grade cement:
43 Grade cement, is the most popular general purpose cement in the country today. The Production of grade 43 cement, is nearly 50% of the total production in the country. 43 Grade cement, are generally used in general civil engineering works, precast items such as blocks, tiles, asbestos sheets etc.
- 33 Grade cement:
This cement is used for general civil construction work under normal environment conditions. Due to low compressive strength, this cement is not normally used where a higher grade of concrete is required. The availability of higher grades of cement, in the market are affecting the use of 33 Grade cement, and nowadays 43 grade cement, is normally used for general Construction work instead of 33 grade PC. More useful mass concreting and plain cement concreting. It can be used for plastering and single storied individual houses.
PORTLAND CEMENT (PC)
PC has 80 per cent clinker, 15 per cent PC cement, and 5 per cent gypsum and accounts For 18 per cent of the total cement consumption. IT is manufactured because it uses fly Ash/burnt clay/coal waste as the main ingredient.
The Portland Cement is a kind of Blended cement which is produced by either inter grinding of cement, clinker along with gypsum and materials in certain proportions or grinding the cement, clinker, gypsum and materials separately and Thoroughly blending them in certain proportions.
Portland cement is a natural or artificial material containing silica in a reactive form. It may be further discussed as siliceous or siliceous and a luminous 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 PC cement, 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 cement materials commonly used are;
• Volcanic ash
• Calcined clay
• Fly ash
• Silica fumes
In view of the availability of good quality fly ash in abundant quality, the use of calcined clay based cement is progressively decreasing. The fly ash is a waste product of Thermal Power Plant which create disposal problems at Thermal power plant site. The yearly Production of fly ash in India is about 70 million tonnes per annum. This would increase in the Future, depending upon the new coal based thermal power plants to be installed in the country. The present utilization of fly ash in production of blended cement in India is meager. Fly Ash is the ash precipitated electrostatically from the exhaust fumes of a coal-fired power station.
The fly ash particles are spherical and are generally of higher fineness than cement so that the Silica is readily available for reaction. The Portland Cement makes concrete more Impermeable and denser as compared to Ordinary Portland Cement. The long term strength (90 days and above) of PC cement is better compared to OC. The Portland Cement is ideally suited for the following construction.
• Hydraulic structures
• Mass concreting works
• Marine structures
• Masonry mortars and plastering
The compressive strength of PPC as it is equivalent to that of 33 Grade PC. The major quantity of fly ash based PPC in India Cements Limited is presently being produced at India Cements Limited at Tamil Nadu. However, depending on the requirement of fly ash based PC could be produced at all the plants of India Cements Limited in Tamil Nadu and Andhra Pradesh. The cement being manufactured by India Cements Ltd meets the strength requirement of 53 Grade.
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