An article on concrete, written by a person described as a successful real estate developer and distributed by a media relations outfit, offers an object lesson on thinking in silos. Entirely missing is a sense of current concerns about the quality of urban life or an assessment of the key role (pluses and minuses) that concrete plays in it. But it is essential for developers to be sensitive to these issues if they wish to have a sustainable business model and not keep being buffeted by developments, inevitably unanticipated.
The article begins by lamenting the popularity of the term “concrete jungle” though concrete has been around for long and has “some excellent attributes which make it very important in today’s context.” It describes concrete as an “eminently environmentally friendly building material… for the construction of sustainable homes.” Concrete uses cement which comes from limestone whose supply is unlimited. But you can replace some of the cement with fly ash or blast furnace slag. As these are wastes generated by the coal-based power and steel industries, concrete helps recycle waste and is therefore “a real boon to the planet”.
On durability, concrete beats other building materials hollow. Another benefit of concrete is its ability to absorb and retain heat. This allows significant saving in both “heating and cooling bills”. In a concrete building, you can “install air conditioners of lower capacity resulting in significant electricity savings”. Concrete, which is “inherently light in colour”, deflects more solar radiation and so makes for less of “urban heat islands”. Further, concrete is made to order and so there is no wastage. And after the life of a usage is over, concrete can be crushed and reused as an aggregate for making fresh concrete.
First, the term “concrete jungle” is outdated, coming from times when a “jungle” was a negative thing. Today, there is far greater appreciation of the utility and beauty of forests — be they temperate or tropical (jungle). Jungle treks are a growing sport and an integral part of eco-tourism. If you wish to decry a heavily concreted area, it is better to refer to it as a bit of “concrete hell.”
Second, concrete is far from environmentally benign. A key ingredient in it is cement (making up 12 per cent of the ingredients needed) whose manufacture has several negative impacts on the environment. It is very energy intensive and is a key emitter of carbon dioxide. Cement manufacturing is the third largest producer of carbon dioxide and four to five per cent of total worldwide carbon dioxide emission comes from cement. Replacing a part of the cement used with fly ash and granulated slag (these can be 50-60 per cent of blended Portland cement) to make concrete, for which there is a great scope, can make a bit difference. But this is mitigation. Cement and concrete did not set out as environmental angles in the first place.
Third, concrete absorbs heat and is slow to give it up. In most of India, in early summer evenings, when the outdoors have become quite pleasant, the inside of apartments remains like ovens. In winter mornings, when the outdoors are sunny and comfortable, the indoors are still chilly and unfriendly. Concrete and asphalt are primary contributors to urban heat islands. There is some mitigation in having light-coloured outward-facing concrete surfaces so that they deflect more solar radiation but that is again mitigation. Of course, asphalt used to make roofs or surface roads is a worse offender but that does not make concrete good.
Fourth, surface runoffs, resulting from concrete surfacing of roads, pavements and parking lots lead to lower ground water percolation and retard ground water recharge. A side effect of concrete terracing along river embankments is soil erosion and flooding. A partial solution is to use porous concrete.
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It is also ridiculous to suggest that you can lower your electricity bill by moving into a concrete apartment and manage with lower capacity air conditioners. Closer to the ideal is to live in an old-fashioned building with thick brick walls, enough doors and windows to allow easy draughts and a tree or two in the courtyard. Then you will be able to do without air conditioners.
All this is not to say that concrete is an unmitigated evil. Quite the contrary. Concrete is the second most used product after water on the planet. It is the most widely used building material in the world. Other than being used to build urban apartments, concrete has, for a century and more, been extensively used in building durable dams and embankments. But here also thinking is changing. More and more, dams are being decommissioned in the US to make rivers come back to life and the basic utility of embankments is being questioned. The negative impact of floods along the Koshi river in Bihar has been worsened, not reduced, by embankments.
Concrete is dear to the heart of builders of tall apartment blocks which maximise their return on investment but strain infrastructure and exacerbate urban problems. But for the concrete industry to achieve sustainable growth it has to shift focus from reducing construction time to conserving energy and material. This can be beyond the scope of builders who work with given processes. So they should stick to their knitting and not get carried away singing to the wonder and beauty of concrete.