Wednesday, August 25, 2010

Underpass: 25-day work, long-lasting technology

nderpass: 25-day work, long-lasting technology
White Topping will give roads of this type a life span of 30 years, while conventional roads hardly last 5 years
Niranjan Kaggere

Bangalore is set to witness a ‘white revolution’. As opposed to tarred roads, which are black in colour, the city will have ‘white roads’ that use the US technology on important stretches and last more than 30 years. Our roads hardly last four to five years.
The ‘White Topping’ technology is expected to be used in 11 signal-free corridors. It uses special concrete and a chemical substance that gives vehicles a firm grip on the road.
This technology has been used for the first time in Bangalore on the Madivala Underpass, which was inaugurated by Chief Minister B S Yeddyurappa on Tuesday.
The underpass, worth over Rs 80 lakh, was funded by the Cement Manufacturers’ Association of India as a demonstration to the state government. It caught the attention of the CM, who ordered use of this technology on 11 other signal-free corridors.
Conventional roads are asphalted with tar along with other materials and look black. In these roads, highquality concrete is used and they look white. Hence the name.
While conventional roads need retarring once in four to five years, roads using this technology will last 30-35 years. The normal roads use a lot of sand and crushed stones. This technology prevents wastage of natural resources. “In this technology, even a half-a-feet thick road gives a lot of strength,” says Nagesh Puttaswamy, regional head (technical), Ultratech Cement.
Cost-wise, the new technology is 5-8 per cent more. On an average, it will cost Rs 400-600 per square metre of road. However, it can withstand any degree of friction.
The cost doesn’t seem to have deterred the government. “Keeping in mind the fact that it lasts longer, we should use the same technology for building other underpasses too,” said the chief minister.
In future, roads will be laid using sophisticated equipment called ‘paver machines’. According to sources in the BBMP, these machines come with rollers for levelling the concrete bed. This machine was used during the construction of Madivala underpass and it costs Rs 94 lakh.
A senior official from the BBMP’s major roads wing, said, “The quantity of water used to build these roads is very less. Only 280 ml of water is used per kilogram of concrete along with other compositions.”
Once the concrete is laid on the stretch, a wax-like concrete-curing compound will be sprayed on it to prevent loss of water. This compound will form a thin film above the road and helps concrete to set firmly in three days. “The Madivala junction, measuring 330X28 metres, has been built within 25 days with 20 hours of work every day,” said Nagesh.


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