If the numbers can be believed, in India, about 15,000 tonne of aggregates are required per kilometre of highway. A typical project of National Highway Development Project (NHDP), of 60 km  of road improvement requires 20 lakh tonne of virgin material. Unfortunately, in India, in most cases, old pavement materials are dumped into landfills; at which point we need to remember that landfills have been identified as the largest source of methane caused by humans. Add to this the cost factor: with bitumen @ Rs 36,000 per tonne and aggregate cost varying between Rs 300 to Rs 600 per tonne, the savings on 2-3 per cent bitumen and aggregates will save the customer millions of rupees.

From the environmental angle, the production of pavement mixes such as hot-mix asphalt (HMA) requires a significant amount of energy, for production of bituminous binder from crude petroleum and drying aggregates. Approximately 1.5 gallon of fuel is used for drying and heating one tonne of aggregates consider that figure in terms of the lakhs of tonnes of aggregates that is used. Another major concern is  that the heating of bituminous binder and HMA releases a significant amount of green-house gases such as carbon dioxide, and harmful pollutants such as sulphur and nitrogen oxides. The amount of emission doubles for every 10oC increase in production temperature, and increasingly, higher tempe?rature is actually being used for the production of HMA with modified binders.

Globally, the past few decades have seen tremendous growth in equipment and techniques in recycling, from milling machines to mixing plants and in-place trains. Plants are now available that are capable of recycling in high percentages and materials, as well as  restoring correct asphaltenes maltene proportions in aged asphalt. Green mixes and low carbon emitting technologies have gained acceptance and applause worldwide for their massive savings in carbon emission and fuel savings.  

There have been amazing developments in hot-mix production technology. Economic crises and environmental concerns have made it imperative to look for sustainable production methodologies. For example, the Fayat Group has developed products and technologies, which can recycle 75-80 per cent of reclaimed asphalt pavements (RAP), produce hot-mix with low impact and reduced carbon footprints up to 30 per cent. Companies like TIL have joined hands with Astec and have brought in double-barrel technology which has been approved by the NHAI. Producing mixes with RAP is a well proven technology reflecting sustainable development. Unfortunately, the awareness of the usage and benefits of RAP is limited to a few. Though there are many fora which discuss the urgent need for the usage of RAP, this message has not been effectively carried to the road construction companies. Not many are even aware of the appropriate use of RAP and are using the same for aggregate replacement, totally ignoring the potential savings of bitumen in the RAP.

The present situation calls for a paradigm shift. The focus of the industry needs to be  on reduction of green-house gases, higher rates of recycling, use of specialised mix designs, operational safety, systems that reduce equipment downtime and bring support closer, and the like.  It is heartening to note that more  professional road-building companies are showing a deep interest in produ?cing high content RAP, warm-mix, low energy mixes, specification mixes, cold-mixes,  etc.

It is a beginning well made. However, to tweak the famous saying a bit, there are miles to go before anyone can sleep.