The use of hot mixing plants is common in developing countries for roads and similar construction works. Such plants emit organic compounds, smoke, black carbon, soot and sulphur oxide that are serious health hazards.
Today, scientists and researchers all over the world are carrying on their research to find out environment-friendly and sustainable technologies for road construction. One such technology is the Central Road Research Institute developed CRRI-Bitchem Cold Mix technology, which is being utilised for black-topping activities of roads throughout India in PMGSY and various government schemes.
It’s a new generation road science technology for rural road construction and maintenance activities that brings environmental friendly benefits like zero pollution, no smoke & heating during black-topping activities and a higher surface compared to hot-mix roads. Till now, the technology has been used in laying over 4,000 km of roads across India.
The cold mix technology
Cold mix technology is field application of mix design based on tailor-made CRRI-Bitchem cold mix binders with the available IRC recommended aggregates, through modified HMP plant or site mixing, without the need for any heating, in an environment-friendly manner.
The technology is a highly engineered but simple and effective solution for road construction and maintenance for rural, district and state roads, requiring a durable all-weather surface measuring 2 cm in thickness over the WBM or old bituminous surface with open-graded premix carpeting.
This surface is an outcome of Bitchem Cold Mix binders containing certain performance additives pre-mixed with graded aggregates (13.2 mm & 11.2 mm nominal size) with 2:1 ratio either at concrete mixer or a centralised pug mill, to provide higher volume of construction and speedy completion of roads by enhancing the quality of the surface.
To provide better surface performance, a binder is used to finally seal the surface with a premix seal coat of aggregates, achieving maximum sealing of the open pores.
The biggest advantage of the cold mix technology is that on an average, precious fossil fuels —approximately 1,500 litres of diesel per km — are saved with an overall savings of construction which is more than 35 per cent. And if over 1,000 km of roads are constructed in a year, in each state, the benefits would be enormous.
Meanwhile, considering 30,000 km annual road construction, cold mix can save the nation 45 million litres and 145.35 million kg in carbon footprint. Initial cost of Green roads, item-to-item, is 10-15 per cent higher and 2-3 per cent of the total project cost. But these roads last 50 per cent longer than hot-mix roads and hence save minimum 35 per cent of the total cost.
- Faster progress using existing facilities;
- Cold application eliminates heating of bitumen and aggregates, saves fuel;
- Green technology is a non-polluting process;
- Construction in all weather conditions, including the rainy season and winters;
- Guarantee of durability — contains anti-stripping agents;
- Energy security — use of less fuel.