With over Rs 700 billion being invested in the road sector in 2010-11 alone, it?s high time we moved up to highly efficient and sustainable technologies that help optimise resources, considerably reduce pollutants and keep to a minimum damage to the environment. The present situation calls for a paradigm shift. The focus of the industry needs to be on reduction of greenhouse gases, higher rates of recycling, use of specialised mix designs, operational safety, systems that reduce equipment downtime and about bringing support closer.Agith G Antony trains his thoughts on the developments of hot-mix technology.

It?s a known fact but is it an acknowledged fact? The total effects of paving for roads and airports must factor in depletion of natural resources and energy, rise in temperature and air pollution and lowering of groundwater and scarcity of drinking water. As per inputs, overall, world transportation represents ten per cent of the world?s gross domestic product, and is responsible for 22 per cent of global energy consumption, 25 per cent of fossil fuel burning across the world, 30 per cent of global air pollution and greenhouse gases. A dismal state of affairs, indeed. Is there a way out?

Infrastructure development, let us face it, will continue to be driven by the road segment. In 2010-11, the total budget from different states for construction and maintenance is around Rs 50,105.52 crore, and the Central government?s outlay is around Rs 26,210 crore. The Government of India, on its part, is identifying projects and putting them on the fast track by prequalifying the contractors, encouraging PPP and BOT projects, etc. However, on the flip side, as we have seen in the past, there have been numerous delays in the project execution and consequently cost over-runs in view of the spiralling costs driven by the fuel rate hikes, causing the project to become unviable for the road construction companies. The key to find solutions will depend on how quickly and efficiently we optimise resources. The industry today recognises the benefits of completing the project on time/ahead of schedule and as a logical consequence is more open to embracing technology that is sustainable and have less of an impact on the environment.

Indian scenario
?Hot-mix technology in India hasn?t moved forward much over the past decade, except the move from traditional drum-mix plants to batch type plants for large NHAI projects. This has marked the genesis of modern road construction activities in India,? says Blesson Varghese, Managing Director, Marini India. He explains, ?India is still predominantly a drum-mixing-based, asphalt producing market. We will have to move towards batch-type mix production as aggregates processing is still a big challenge in our widely diverse terrain. Although batch plants cannot correct the aggregates, they offer higher quality control due to their screening and gradation post drying, as compared to drum-mix plants. This is the main reason why batch plants were made mandatory by NHAI on large projects.? Blesson further adds, ?Batch plants offer a greater flexibility compared to drum plants. Batch plants can produce a different mix with each batch, which is impossible on a drum-mix plant. Changing hot-mix designs need to add mix enhancers and additives, makes the present drum mixing plant technology in India worthy of a long overdue and respected burial. The drum plant technology presently existing in India is over 30 years old. There is hardly any improvement when compared to the leaps drum mixing technologies have made globally. The existing drum designs cannot ensure bitumen quality and quantity. Moreover, if basic environmental standards are applied other than SPM levels, like standards VOCs, OHs, hazardous air pollutants, these parallel flow drum mixers would stand no chance.?

According to Blesson, pollution control is almost non-existent on drum plants in India. Wet scrubbers have become outdated in most countries decades ago. The drum plant technology in India will have to undergo massive refinement to be able to use bag house type filters and deliver emission to the ever-rising standards. Hence, with the present scenario, the only option is to move towards batch plant technology, which will allow the production of asphalt mix with a lesser impact on the environment.

R Nandagopal, Vice President, Equipment & Project Solutions, TIL, begs to differ. ?The success of double- barrel technology globally is a classic example of the evolution of the drum-mix technology. The capability of the equipment to use up to 50 per cent reclaimed asphalt pavement (RAP) without any modification, and the ease with which the plant can be operated, is the reason for the success of double-barrel technology. In India, this technology has been approved for use by NHAI and the motivation to use RAP with ease, is encouragement enough for a customer to embrace this offering, as it would substantially lower the cost of road construction and also help preserve the environment. As proved in many countries, the drum-mix technology will pave the way for the future in India as well,? points out Nandagopal. He adds, ?TIL in collaboration with Astec Inc has brought the double-barrel technology to India and this technology, we believe, will revolutionise road construction in India. The key to the success enjoyed by this technology globally is the usage of RAP. The six-pack, double-barrel portable plant is available in capacities ranging from 200 TPH to 400 TPH; to meet customer demands of even bigger capacities, the double-barrel can be made available in both the re-locatable and stationary versions.?

Use of RAP
Producing mixes with RAP is a well proven technology reflecting sustainable development. Explains Blesson, ?High content RAP processing and production of other advanced mixes like warm-mix, low-energy asphalt, combination of RAP and warm-mix, etc,  is quite easy on batch plants. All these factors are pushing discerning road professionals towards batch mixing technology. A good quality asphalt plant usually stays with a company for over 20 years. When we supplied asphalt plants in India, although our customers didn?t have long-term vision of the industry trends, we as leaders with a commitment to sustainable development, did have a clear vision. And so our plants are all equipped with minimum 30 per cent RAP processing capabilities, which can be enhanced to up to 45 per cent very easily with a small add-on kit.?

Blesson elaborates further, ?The equipment does not simply decide the percentage of RAP. There are numerous complex factors that must be considered before adding RAP into the asphalt mix. I believe that the present norms laid by the ministry are very practical and easily achievable. However, drawing from worldwide experience in road construction, it surely would benefit India if higher rates of RAP processing are permitted. The Fayat Group has Europe?s best drum mixing plants which have had numerous patents, and they continue to be the leader in the European market. Our drum-mix plants have RAP processing capabilities of up to 70 per cent and consume less energy compared to others in the market. The higher the content of RAP, the more knowledge and laboratory set-up you need for the recycled asphalt pavement. However, our experience with RAP processing and knowledge about Indian site conditions and RAP quality restricts us from offering this product for obvious reasons. Once we are convinced about the readiness of the market, the high-tech drum mixing plants will be launched.? Says Nandagopal, ?The awareness of the usage of RAP is limited to a few road construction companies. The organisations do know that they are sitting on a gold mine but the knowledge to use the RAP the appropriate way is still coming in. Further, the cost of technology is also perceived to be a constraint though the payback is very quick. The other reason could be the conservative approach being adopted by the users who thereby lose out on the first mover advantage. While there is a definite awareness that technology has been successful all around the globe, our possible conservative approach has prevented the same from being successful at home.?

He further adds, ?We, at TIL, create as well as optimise every opportunity to engage with the customer and to also share the best practices and case studies that are being followed globally. With the size of the projects growing under PPP/BOT, it would only be prudent to save on the project costs by adopting the right technology. Specific to the double-barrel, this is a combination aggregate dryer and mixing unit separated from each other uses sequential mixing to produce larger volumes of consistent and homogeneous hot mix in a shorter time than any other plant. It is also equipped to provide multiple job mixes at a very short notice. The features like Accuswipe, dual fuel modulating burners, infrared sensors to maintain heating of aggregate at specified temperature, ability to handle larger dust/ exhaust volumes, ease of operation and maintenance, availability of spares parts, ability to run up to 50 per cent RAP and the optional attachment to produce warm- mix asphalt with foamed bitumen, all give a leading edge to this technology.?

?NHAI has been strongly advocating the use of RAP but unfortunately the message is yet to reach the target audience. We have been surprised often when the customer expresses his ignorance on the NHAI position on the usage of RAP. Globally, many countries have been using RAP consistently and have gone way ahead in terms of percentage usage of RAP used in the hot-mix asphalt. NHAI should advocate a higher percentage usage of RAP to get their target audience interested. From our end, we will continue to work on the subject, share the best practices and extend all support to the agencies that are advocating the usage of RAP,? points out Nandagopal.

He adds, ?TIL has taken the initiative to import the first equipment into India with an objective to deploy the same on rentals; it should be commissioned during October 2011. This will support the technology offered by us and the benefits that will accrue to the customers. In a country which has been using the batch technology for a long time, our biggest challenge has been advo?cating the double-barrel technology. Though NHAI has approved the double-barrel technology, there is still possibly a fear of the unknown which is preve?nting them from using it.?

?The global change in environment and economy is now forcing us to look at sustainable development. Unless road-building profe?ssionals don?t go green, they will not be able to survive. We are excited to find that more professional road-building companies are showing interest in producing high content RAP, warm-mix, low-energy mixes, specification mixes, cold-mixes, etc,? says Blesson.

Nandagopal sums it up on a positive note. ?The future looks very optimistic. Demand for better infrastructure is a very basic requirement and we are still at a nascent stage of infrastructure development in India. There is potential and the opportunity lies in the fact that we still have only two per cent of the road network as expressways. We have just seen the tip of the iceberg; in the future, the only way the HMA industry will go is up.?