Cement, the versatile compound, is the ubiquitous ingredient that is used in any modern construction. While the coarse aggregates like rock pieces, sand and steel give the structure and mass to a building, it is this talcum powder like substance that holds all these material together.
“Cement is known as a binding material that holds all compounds together. Because of its importance one should be careful in choosing the type of cement one uses,” construction material expert L. H. Rao says. Name any material in a construction and cement will be present in it. Cement when mixed with water becomes a binder and when sand is mixed with this binder it is becomes a mortar. “When you include rock pieces into the mortar it becomes concrete and finally when one introduces steel into this compound you get reinforced cement concrete,” he explains.
Cement is the basic substratum of all the building materials and there are many varieties of cements in the market, but people do not have a proper understanding of this crucial compound, Dr. Rao says. Of late there has been a lot of technical developments in cement manufacturing and for a durable building one should select the correct variety, he points out.
To understand what type of cement is to be used, one should first understand how cement is manufactured and one need not be a rocket scientist to do this. Lime stone is the basic material that is used in manufacturing cement and this gives the strength to a construction.
“It is the amount of lime stone in a particular variety of cement that determines its type and it is this proportion (of lime stone) that plays a key role in ensuring the long term stability of a building,” Dr. Rao explains.
The highest concentration of lime stone is available in what is commonly known as Ordinary Portland Cement (OPC). OPC comes with grades like 33, 43 and 53. “Because lime stone is present in high concentrations in OPC, the construction made with this cement gains strength very soon and hence many builders choose this cement when compared to others,” Dr. Rao says. But though this cement gives strength quickly, it may not be the best option that one can choose, he opined.
Though lime stone gives strength, in long run it can react with the elements in atmosphere and result in what is called ‘Lime Leeching’ causing cracks in a structure. “By excessive reliance on quick strength, we may be loosing on the durability of a structure,” he says.
But we do have other variants of cements in the market that have beneficial effects. When a portion of lime stone is replaced with fly ash, the resulting cement is known as Portland Pozzolana Cement (PPC). And Portland Slag Cement (PSC) is made when a part of lime stone is replaced with slag.
While fly ash is a residue that gets accumulated by burning coal in thermal power plants, slag is the by-product that results in the process of steel manufacturing. “The slag and fly ash brings in new elements into the composition of cement and hence reduce the possibility of lime leeching. Though the constructions made with these cements take time to gain strength, durability of structure goes up as these new chemical elements form additional bonds to give strength,” Dr. Rao explains.
Most masons and engineers often advise that 53 grade OPC should be used for all types of the constructions. And as owners are anxious for a ‘strong’ building they too have no qualms to buy ‘highest’ grade cement available in the market.
Though the price difference is very little, a person should be careful while choosing the type of cement that is being used, Dr. Rao adds.
