Correct quality cement goes a long way in making the buildings last long. However; selecting the right grade of cement is not always easy. Below is an attempt of explaining the various grades of cement present in the market today.
There are different types of cement that should be used for specific purposes. Durability characteristics, functional requirement of the building and the environmental conditions play an important role in determining which grade of cement should be used. Checking the grade of the cement is the best way to assess its quality and strength after 28 days of its application. There are three main grades of cement being used in India-53 Grade, 43 Grade and 33 Grade respectively.
Types of Cement
For engineering purposes, there are many types of cement but in general, ‘Ordinary Portland Cement’ (OPC) which is available in three grades should be used for house construction.
33 Grade Ordinary Portland Cement
This ordinary ‘Portland’ cement is used maximum in the country. It is more suitable cement for masonry and general concrete works where the members are not taken to very high stresses. It is not suitable where ‘Sulphate’ is in the soil or in the ground water.
43 Grade Ordinary Portland Cement
43 grades of cement are used where high early strength in 1 to 28 days range is required. These days the ‘Structural Engineers’ propose these cements mainly for RCC works where a member takes high tensile stress.
53 Grade Ordinary Portland Cement
53 grades of cement are used where high early strength in 1 to 28 days range is required. These days ‘Structural Engineers’ propose these cements mainly for RCC works, where a member takes high tensile stress.
Caution in the use of 53 grade cement in construction:
The strength of 53 grade cement does not increase much after 28th day because of early gain while 33 grade cement continues to gain strength after 28th day.
In addition, due to faster hydration process, the concrete releases heat of hydration at much faster rate initially and release of heat is the highest in case of 53 grades. The heat of hydration being higher, the chances of micro-cracking of concrete is much greater. Thus during initial setting period of concrete, the higher heat of hydration can lead to the damage of micro-cracking within the concrete which may not be visible at surface.
This cracking is different from shrinkage or cracks which occur due to faster dryness of concrete in windy conditions. The situation can be worse when we tend to increase the quantity of the cement in concrete with a belief that such increments are better for both strength and durability of concrete.
Thus it is very essential to be very careful in advance that higher grade cement specially GRADE 53 SHOULD be used only where such use is warranted for making the concrete of higher strength and also where good quality assurance measures are in place by which proper precautions are taken to relieve the higher heat of hydration through chilling of aggregates or by proper curing of concrete
How to check the quality of Cement
Make sure that the cement is free from ant dust or lumps.
Take a handful of cement and put that in a bucket of water. If the cement floats in the water for a while before sinking, then it is of superior quality. Sometimes, the cement may sink real fast. This happens due to the presence of impurities.
Cement being used should be within 6 weeks from the manufactured date.