We see many advertisements of cement brands claim that the strength of cement is superior enough to last generations. We have even seen advertisements where an elephant fails against the 'mighty' cement. Are non-civil engineers really buying it? The attempt of this article is to bring to light some basic concepts so that a home promoter is not misguided into spending a premium wrongly thinking that him spending more will ensure a better and stronger home.
What is the purpose of cement?
Cement is a material that hardens and binds together or adheres other materials together. In the case of concrete, cement adheres aggregates. In case of mortar, cement adheres sand. The key point is that cement is rarely used alone.
What is strength of cement?
Let me attempt explaining this in simple words. Strength of cement is a measure of how much stress it can take before breaking. The above statement may not be an all encompassing technically accurate one but it serves the purpose of this article and suit the intended readers.
How cement gets its strength?
This is a key point.
Cement gets its strength from the chemical reaction that starts the moment water is added to it. This reaction is an exothermal reaction, which means heat gets expelled from the reaction.
How is the cement strength measured?
I love the standardization of the measurement principles. It makes life of a civil engineer or even an end consumer so much easier. In simple terms, cement strength is expressed as grade. There are 3 grades - 33 grade cement, 43 grade, 53 grade cement though we come across only 53 grade cement these days. I do not think I have used anything else in my career.
53 grade cement means that the cement would achieve 53 N/sqmm strength (please read above part on strength again) at the end of 28th day for 95% cases.
So what does this mean?
This is the critical point
Irrespective of the advertisement statements, going purely on strength basis, 53 grade cement of Brand ABC or Brand XYZ all mean that a strength of 53 N/sqmm would be achieved at the end of the 28th day.
Difference in types of Cement
So what is the difference in cements if the strength is not a variable. Here is where the strength achievement times becomes the measurement parameter. Some cements achieve the strength much quicker than 28 days. However, one point needs to be mentioned here. There are 2 types of cement available in the market for the same 53 grade. PPC and OPC.
What is the difference between PPC and OPC ?
The primary difference is the component of this. PPC has fly ash content which makes it an environmentally responsible product. It is relatively a new product. The heat of hydration and subsequently the strength gaining is slower in case of PPC which makes it easier to handle.
Conclusion - For a home promoter
If you spend money for premium cements, please understand that the strength achievement is the same across any reliable brands after 28 days. How you should choose cement actually depends on the methodology of construction. In a case where OPC and quick strength gaining cement is being used, the contractor/builder should be equipped to provide fully attentive curing for the duration of the strength gain. This is a very largely ignored item particularly because of lack of awareness and gross neglect. I would recommend that unless there is a very clear reason for usage of quick hardening cement, normal PPC cement of any brand would suffice as long as a proper technically qualified civil engineer is supervising the works.