BEWARE OF EXCESS CEMENT
Cement deteriorates with age, and has an inherent weakness of cracking.
How many of us know that India is the second largest manufacturer of cement in the world with more than 360 million tonne annual capacity? Is it a matter to be proud of? Majority will say, yes. The price of cement has come to indicate the health of market economy, shifting directions of monetary investments, rate of infrastructure development and such others. Again, an important information for all of us.
How many of us know that every tonne of cement produced causes nearly another tonne of carbon dioxide, a major contributor to greenhouse gases? Is it a matter to be proud of? This time hopefully, majority will say ‘no.’ This is besides the fact that cement also has very high embodied energy, a major concern today in sustainable buildings. If so, how should we treat this wonder material?
Cement is a product of calcium, aluminium, silicon and iron, supplied through mainly limestone, clay and sand. The mix in right proportion with more than 3/4th limestone is grinded, pre-heated and then heated up to 1400 degree centigrade in a rotating furnace kiln, where decarbonation takes place, releasing carbon dioxide, slurry and clinkers. The clinkers are set into a horizontal chamber for final and fine grinding.
Within about 200 years of its discovery, cement has conquered the world of construction, due to its versatility of usage, flexibility in design applications, strength and setting time.
While professionals may handle it more efficiently, even a village mason picks up the skills of working with cement very fast, hence its popularity. However, thanks to its popularity, we appear to be ignoring its drawbacks.
Though lime and cement share common raw material, cement deteriorates with age, while lime stays fit for long. Cement has an inherent weakness of cracking, passing on this trait to concrete too. As such, experts do not guarantee a cement and concrete building to last more than 60 to 80 years without periodic improvements.
Besides, it absorbs heat if directly exposed to sun, with surface cracks. If we checkout any building with only cement mortar plastering without wall paint, hundreds of cracks can be seen on the surface. Normal mortar tends to absorb water, being groscopic in nature, hence requires varied water-proofing applications. Traditional buildings in stone, wood, non-homogeneous roofs and such others could withstand minor settlement in site or even small-scale earthquakes. In contrast, cement as a material is not good to withstand settlements.
Despite knowing about the drawbacks of cement, we end up having cement mortar in all joints and surfaces; concrete in foundation, columns, lintels, beams, slabs, frames and coping bands; cement blocks in walls. What we are building today appears to be a cement building from head to toe.
While it is a dangerous trend in construction, it is equally a shame on us to neglect dozens of appropriate materials available to us. Once cement was a boon, today it may not be. It is time to look outside cement.