Basics of building materials - Cement decoded
Before putting our hands into cement, let’s arrive at unison as to what is cement.
First of all, cement is not concrete. Cement is not mortar.Cement + aggregates + water = concrete.Cement + sand + water = mortar.
Now, what is cement?
Cement is a binding agent that binds aggregates to make concrete and mortar.
Next, what is cement made of?
Cement is made of limestone, clay, gypsum and other materials.
By the way, who invented cement?
While the use of a binding substance, a cement-like substance in construction dates back to the Babylonians era, William Aspdin invented the modern Portland cement – the most common type of cement.
The secret behind the name
The cement which was called proto-Portland cement, invented by Joseph Aspdin, the father of William Aspdin, looked like the prestigious Portland stone from the Isle of Portland. Hence, the cement is called Portland cement.
Types of cement
There are nearly 13 types of cement.Ordinary Portland cement, Portland Pozzolana cement, rapid hardening cement, quick setting cement, low heat cement, sulphate resisting cement, blast furnace slag cement, high alumina cement, white cement, coloured cement, air entraining cement, expansive cement and hydrophobic cement.Though the list is exhaustive, Portland cement is the most commonly used cement.
How is cement classified?
The Portland cement is classified as grade 33, grade 43 and grade 53.Grade 33 – General concrete worksGrade 43 – RCC work and where high early strength is requiredGrade 53 – Where faster initial strength is required
The shelf life…
It depends on storage methods. However, the compressive strength of cement gradually decreases over time.
How much time will it take for the cement to harden completely?
Generally speaking, it’s not more than 10 hours.
But, when it comes to timeframe, two phenomena play an important role: Initial setting time and final setting time. Initial setting time: It is the amount of time between two events:
1. The moment the water is added to the cement.
2. The moment cement starts losing its plasticity.
It should not be more than 30 minutes. The process of mixing, placing, compacting and finishing should be finished within that timeframe.
Final setting time:
It is the amount of time required for the cement to lose its plasticity completely and harden sufficiently. It is around 10 hours.
Tips for buying cement
Cement is arguably the most important material in the process of construction. While we can decorate our walls and floors in myriad ways, what is inside is important than anything else. While the look and feel of the house is determined by many other materials, the strength of the building is largely dependent on cement.
So, when you buy cement, bear in mind the locality and climatic conditions of the site. Do research. Seek expert opinion. Buy what is needed; neither more nor less. Store the bags in a dry place where there is little or no moisture. Buy only the best. Because, your house, for the most part, will be made of cement.