Know abouts of cement
From an engineering perspective there are numerous types of cements but in general construction work, the cement used is Ordinary Portland Cement. Ordinary Portland Cement is available in 3 grades, all of them can be used for construction.
Types of cement Grade
There are 3 types of cement Grade;
- 33 Grade Ordinary Portland Cement
This basic Portland cement is the most common grade of cement used in India. It is most suitable for masonry and ordinary concrete works in which the constructed members need not require to withstand high amount of stress. It is not very expensive and is readily available. This type of cement is not suitable for construction where Sulphate chemical is present in soil or ground water.
- 43 Grade Ordinary Portland Cement
This type of cement develops early strength at 3 to 7 days with exceptionally high 28 days strength. Its higher characteristic strength means higher bond strength and massive reduction in the possibility of slippage of reinforcements. This cement prevents leakage or seepage. It can be used at sites where there is high Sulphate presence. This type of cement attains the compression strength of 43 MPA (Mega Pascals) in 28 days of setting.
- 53 Grade Ordinary Portland Cement
This type of cement has high composition of C3S (Tri Calcium Silicate). It provides flexibility and leads to a sleeker design and easy construction.This cement develops early strength which results in faster construction. Having negligible chloride content, this cement restrains corrosion. Its high early strength also helps in saving the quantity of cement used. 53 Grade cement has fast setting compared to 43 Grade cement. 53 Grade cement attains 27 MPA in 7 days to 23 MPA by 43 Grade.
Blended cements
Blended cement is obtained by blending of Ordinary Portland Cement with mineral mixtures or additives like fly ash, slag or silica fumes. This type of cement has numerous advantages.
Advantages
- Reduces water demand, helping in reduce water-cement ratio.
- Blended cement, being finer as compared to OPC, has less permeability of concrete.
- Mineral admixtures which are used in making blended cement are actually waste products of thermal and steel plants. This helps in recycling and conserving.
- By reducing the production of cement, the pollution is also controlled as cement is an energy intensive product.
Blended cements: advantages over OPC cements
- The strength of blended cement increases continuously with time while that of OPC cement decreases.
- The resistance of blended cement is far more superior than OPC cement against Sulphate and other forms of corrosion.
- Blended cement is easy to work with as compared to Portland cement.
- Better cohesiveness of fresh concrete in the case of Blended cement provides more stability.
- Cases of thermal cracking due to heat of hydration are nil in Blended cement when compared with OPC.
- Blended cement provides better water tightness and less seepage.
- Alkali-Silica hardly react with Blended cement and results in higher shell life of the structure, as compared to OPC.
- OPC cement shrinks a lot after drying but the drying rate of Blended cement is less.
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