Nearly 50,000 km of national highways have been added in India since 2014. Besides, the pace of construction more than doubled, from 11.6 km per day in 2013-14 to 28.3 km per day in 2022-23. Rapid population growth, infrastructure development and industrialisation have led to an increase in not only demand for traditional construction materials but also the quantity of the waste generated. To this end, various alternative and sustainable materials are now being deployed for road construction in the country. Materials such as fly ash, demolition rubble, plastic, bitumen, municipal and industrial waste and geosynthetics are being increasingly used for road construction.
Government impetus
Sustainability and safety have taken centre stage in recent times in a bid to reduce the environmental impact of construction as well as road fatalities. The Ministry of Road Transport and Highways (MoRTH) has been promoting the use of sustainable practices. It has issued guidelines on February 6, 2023 for road construction agencies at the central and state levels, making it mandatory to use plastic waste in the construction and repair of service roads and slip roads along national highways. The idea is to make road construction more durable, cheaper, stronger and sustainable, and pothole-free. This step will also make it easier to dispose of urban plastic waste.
In the new guidelines, the government has made it mandatory to use plastic waste in the construction and repair of service roads along national highways, within a radius of 50 km of urban areas, having a population of over 0.5 million. For this, collection centres will be established for plastic waste at various places so that it can be transported to the hot mix plant and may be used further as and when required.
The government is also promoting the use of precast concrete elements in road and bridge construction. Under the National Highway Precast Concrete Policy announced last year, a minimum of 25 per cent of the total concrete volume other than foundations and substructures of bridges/viaducts/road overbridges for new construction, reconstruction and widening must come from factory-manufactured precast concrete elements, if such a factory is there within a 100 km distance from any point on the project. This policy decision aims to reduce pollution at construction sites, along with accelerating work completion and improving aesthetics.
Use of alternative materials and innovations in construction techniques
The Government of India and the World Bank have signed an agreement for the construction of the Green National Highway Corridors Project (GNHCP), with a length of 781 km, in Himachal Pradesh, Rajasthan, Uttar Pradesh and Andhra Pradesh. While the total investment required for the GNHCP stands at $1.3 billion (Rs 76.62 billion), loan assistance of $500 million will also be required for the project. The objective of the GNHCP is to demonstrate safe and green highways, keeping in view climate resilience and the use of green technologies by incorporating the provisions of natural resource conservation. The use of cement-treated sub-base, reclaimed asphalt pavement and marginal material such as lime, fly ash, waste plastic as well as bio-engineering measures for slope protection such as hydro-seeding, coco/ jute fibre will enhance the ability of MoRTH to bring green technologies into mainstream road construction.
In June 2022, Surat became the first city in the country to construct a processed steel slag (industrial waste) road, built as part of a joint venture project between the Council of Scientific and Industrial Research, the Central Road Research Institute, the Union Ministry of Steel, NITI Aayog and ArcelorMittal Nippon Steel at Hazira. The use of steel slag technology in paving the roads is in line with the vision of “waste-to-wealth”. This innovative technological initiative also addresses the problem of environmental degradation caused by waste steel slag and unsustainable mining and quarrying of natural aggregates. The stretch of a six-lane road experimentally paved with slag from the steel plant has been shown to resist beating from the weather as well as from thousands of heavy trucks, even though the surface is 30 per cent shallower than that of roads paved with natural aggregates.
In a similar development, the Border Roads Organisation (BRO) used steel slag to construct a long-lasting heavy-duty road in Arunachal Pradesh along the India-China border area. Supplied free of cost by Tata Steel Limited, the steel slag material was transported from Jamshedpur to Arunachal Pradesh by Indian Railways. Apart from this, the National Highways Authority of India (NHAI) has successfully tested the steel slag road technology on the Mumbai-Goa National Highway (NH-66). Steel slag roads last 10 years as compared to three to four years by bitumen roads, thus reducing the maintenance costs by a huge margin.
Bitumen is also a popularly used alternative road construction material. NHAI has deployed the new bitumen technology to increase the longevity of the Delhi-Mumbai Expressway. In another development, the reuse of plastic waste is also becoming popular in road construction. To this end, several thousand kilometres of highways have been constructed using plastic waste. In 2022, a connecting road between Ecoworld and the Outer Ring Road was constructed, using 3,000 kg of recycled plastic waste in Bengaluru. Crafted entirely from 100 per cent recycled waste, these roads are eco-friendly and durable. There has been a rising trend of recycled plastic waste being used in road construction as a more sustainable and eco-friendly alternative to traditional materials. Apart from this, plastic waste roads are being built in cities such as Delhi, Chennai, Pune, Jamshedpur, Indore, Lucknow, etc.
In a bid to reduce the carbon footprint, the Centre is currently working on developing electric highways as well. These are electrified roads that recharge batteries of electric vehicles driving on it. A pilot project on the Delhi-Jaipur Highway extended from Delhi Urban Extension Road named UER-II is being planned on similar lines.
Key achievements using sustainable materials
Over the past few years, the road sector has witnessed several remarkable achievements. In May 2023, India
achieved a milestone by laying 112.5 km lane of bituminous concrete road within a time frame of 100 hours. Such roads are typically constructed in distinct layers composed of materials such as asphalt, soil, stone aggregates, bitumen and cement.
In Maharashtra, the construction of a 75 km single-lane bituminous concrete road on the Amravati-Akola section of NH-53 was completed in 105 hours and 33 minutes (4.5 days). In a similar development, laying of the highest ever quantity of 43,000 tonnes of dense bitumen mix (DBM) over a 50 km single-lane road in 100 hours was achieved on the Delhi-Vadodara Expressway section of the Delhi-Mumbai Expressway.
The road ahead
The construction industry across the globe is promoting the use of innovative and sustainable materials with the aim of reducing the environmental impact. The Indian government has undertaken various initiatives such as eliminating pre-construction obstacles, expediting project execution and supporting new technologies with the aim of enhancing construction quality and building resilient roads. The government is now laying emphasis on the use of various alternatives for reducing the carbon footprint of the sector, and new construction materials including modified bitumen, fly ash, plastic waste and steel slag are gaining traction. Going forward, the adoption of smart and sustainable road construction techniques is essential to switch from conventional materials and help the country achieve its net-zero targets.
Disha Khanna
