Chennai: With the hot bitumen mix plants that are used in laying roads coming under the focus of the Tamilnadu Pollution Control Board (TNPCB) for causing pollution, experts from the highways and environment sector welcome the move: they claim it will drastically change the way roads are laid.

TNPCB will be conducting an aerial survey this month and eventually complete the framing of guidelines governing these units based on an order from National Green Tribunal’s (NGT’s) Southern Bench here.

The bench was hearing an application which sought to seal seven hot mix plants near Sriperumbudur. They were closed down by the board for violating norms but continued to operate clandestinely at night.

Environmentalist Nithyanandam Jayaraman says, “Anything that is done for saving the environment is a good sign. Though I have little knowledge about the hot bitumen mix plants, any machinery or plant that uses fossil fuel definitely causes pollution. I am hearing for the first time that the bitumen plants have come under the purview of the pollution control agency of the State. The outcome of the survey will be an eye-opener for everyone, but the government departments, like highways and local bodies must follow the directive.”

Bitumen is best suited for road building in terms of cost of production, and it takes very less time for the workers to build a path with bitumen than any other form of road as it dries quickly. Since bitumen is a recyclable material, it can be re-used by melting. Moreover, whenever a pothole or crater appears on the road, it is very easy to repair.

The structure and thickness of the material makes it even easy to be re-layered over the old layer. They also provide better traction and skid resistance during commuting. But the small readymix hot plants used by the workers is a cause for concern. Many contractors use them at night for laying roads. Since the entire process involves heating bitumen, it causes air pollution. Despite this, for many years, bitumen plants never came under the purview of environmentalists or the pollution control agency.

Association of Tamilnadu Highway Engineers president and Highway Research Institute (Guindy) Deputy Director, A Venkatachalam, says, “This is first time I am hearing news about bitumen causing pollution. But I can say that bitumen plants work under the complete supervision of the authorities. Even the road contractors using such plants must fulfil criteria, and their quality is constantly checked. But I welcome the decision of the Tamilnadu Pollution Control Board for an aerial survey to study the pollution level and its plan to frame guidelines for hot bitumen mix plants. Because bitumen plants do cause pollution, anything that is done to safeguard nature must be welcomed.”

While bitumen plants have become a hot topic, road experts feel it is high time concrete was used as an effective replacement for bitumen as it doesn’t harm the eco-system. But some feel that concrete and bitumen have their disadvantages.

Listing out the points, Association of Tamilnadu Highway Engineers secretary R Deepak says, “While concrete is environment-friendly and long-lasting, it it has its limitations: constructing a concrete road is expensive, compared to bitumen. In case there are craters or cracks, the whole slab must be replaced or repaired. During rainy season, vehicles tend to slip or sometimes slide which might lead to accidents.”


Bitumen mix plant is a road construction equipment used for heating and mixing of aggregates, sand, gravel and stone dust. First the materials are heated at very high temperature of up to 1,000 degrees centigrade and then an appropriate proportion of bitumen is mixed in standard temperature and then it is transported to the work site for laying roads. There are two types of bitumen – one that occurs naturally and one that is derived by the distillation of petroleum.