The road sector is undergoing significant transformation due to the growing demand for sustainable transportation networks. With the increased scope of road construction, the sector is focusing on alternative construction materials and smart technologies to ensure sustainable and quality output. The Ministry of Road Transport and Highways (MoRTH) and the National Highways Authority of India (NHAI) have been instrumental in advocating and promoting sustainable practices.
Key contractor initiatives
Contractors are actively participating in and contributing towards sustainable construction while ensuring safe mobility. For instance, GR Infraprojects Limited is actively utilising plastic waste for the construction of roads. Recently, the firm also incorporated glass fibre reinforced polymer in concrete pavements. Further, it plans to implement geosynthetic reinforced pavements.
Crash barriers are a crucial component of safety, and GR Infraprojects engages in the production and manufacturing of its own crash barriers. The company has its own internal team for design, implementation and safety audits in addition to the necessary safety audits undertaken by NHAI, with effective coordination among all internal teams. It also identifies and addresses possible locations that are susceptible to the occurrence of black spots.
Larsen & Toubro Limited (L&T), another key road construction firm, is constantly testing new technologies. The firm has a dedicated centre for excellence for examining new materials and technologies, which are then considered for projects after consultation with clients. Any new learnings are shared publicly, as technology transfer remains a key driver for sustainable construction.
Sustainability measures
In order to achieve sustainability, it is crucial to implement the principles of reduce, reuse and recycle. The utilisation of new materials in road projects needs to be minimised. While it may not be possible to completely eliminate their use, the key is to design the project in a way that requires the least amount of materials. This applies to various materials such as earth, aggregate, sand and steel. Furthermore, it is critical to optimise the reutilisation of materials deployed in road construction. For instance, rain cuts can cause erosion of the earth from the embankment. However, instead of restoring the rain cuts by bringing in fresh material, it can be more efficient to utilise the material already available within the project.
Likewise, any damage to pre-cast ought to be repaired and rectified rather than replaced, given that 1 kg of cement emits 900 grams of carbon dioxide and deploying new concrete would contribute to the overall emissions. Similarly, 1 kg of steel emits approximately 1,500 grams of carbon dioxide. Due to this, “reuse” emerges as a critical area of emphasis. Furthermore, if an item cannot be reused, it must be recycled to enable the creation of new material from it.
Approximately 60-70 per cent of the energy consumed in highways is attributed to the extraction of materials. This can be reduced by adapting to the available local resources. When designing roads, it is important to take into account the availability of local materials. The use of items not readily accessible locally can result in a higher carbon footprint due to transportation.
Solar blinkers are now installed at every road junction. These blinkers consist of various components such as solar panels, batteries and LED panels. In case of malfunction, it is essential to identify, address and restore only the specific defected component rather than replacing the entire solar blinker.
There is a significant focus on the use of clean fuels and the adoption of electric vehicles (EVs). It is imperative to transition away from diesel and petrol to compressed natural gas and EVs. Notably, there is an ongoing study in the US about electrified pavements, which can generate electricity and power EVs when cars pass over them. A similar study should be conducted in India to explore the potential of generating electricity from these pavements.
Black spot rectification
The occurrence of black spots should be considered during the design stage itself. For instance, when designing and finalising the alignment, it is important to avoid sharp curves and steep gradients in combination with sharp curves to minimise the occurrence of black spots. During the construction phase, the design should be executed accurately, as any modifications after design finalisation could contribute to the development of black spots. Similarly, throughout the operations and maintenance (O&M) phase, it is important to ensure that there are no substantial modifications in the project’s alignment. Frequently, instances of encroachments lead to the establishment of black spots, subsequently contributing to accidents.
Another essential factor to consider is the presence of adequate lighting. Any alterations in lighting patterns should be promptly addressed. Further, the issue of road sign visibility is a major concern, with road signs often obstructed by vegetation. It is crucial to address this matter through regular maintenance efforts. By doing so, black spots can effectively be reduced.
Challenges encountered
GR Infraprojects utilises construction and demolition (C&D) waste, municipal waste and steel slag for embankment purposes. However, occasionally, the accessible waste material is located beyond city borders. For instance, the company recently expressed its intention to use the C&D waste produced at a Burari plant in New Delhi. Nevertheless, crossing the Delhi border necessitated payment of taxes without any waivers. Due to this, the available waste material was not fully utilised. To address such issues, government entities must collaborate and cooperate to ensure the optimal usage of existing waste materials.
A standard pavement quality concrete pavement has a thickness ranging from 300 mm to 320 mm. This can be reduced by utilising short panel concrete pavement. Furthermore, the utilization of bonded rigid pavement enables a significant reduction in thicknesses, amounting to 60 mm. This results in substantial savings in energy, materials, aggregates and transportation costs.
Another challenge is the absence of technology transfer. In meetings convened by MoRTH and NHAI with suppliers and vendors, including bitumen and geosynthetic companies, the contractors and end users are often not present. This results in the non-dissemination of experience and the failure to facilitate technology transfer for firms lacking the expertise of more experienced counterparts.
For instance, knitted or woven geogrid and extruded geogrid are two varieties of geogrid. Knowledge about which one operates at the subgrade level, which one operates at the granular sub-base (GSB) level, and which one operates at the wet mix macadam level is often confined to the firm that employs them. Another example is the perpetual pavement on the Delhi-Vadodara expressway, which failed shortly after its inauguration due to a lack of knowledge sharing. Hence, construction experiences should be shared and workshops must conducted to facilitate the transfer of best practices and learnings.
Further support needed
Currently, contractors encounter challenges in implementing newer, cleaner technologies and using sustainable materials. For instance, in any project, after convincing the authority engineer of the technology’s suitability, the matter is subsequently forwarded to NHAI or MoRTH for clearance. The implementing agencies grant permission, provided that the contractor assumes responsibility along with an extended defect liability period. Consequently, contractors do not receive benefits, carbon credits or recognition for their efforts.
In addition, they are overwhelmed with an excessive number of years of maintenance. This is the primary reason why contractors and concessionaires are hesitant to adopt new technologies. Similarly, sustainable materials such as green cement and green steel are not included in the codal provisions. Hence, contractors take on the risk associated with using these materials.
Overall, greater regulatory support is crucial to encourage contractors to actively adopt sustainable technology and materials, thereby enabling them to make a more significant contribution to the government’s overarching objective of creating sustainable infrastructure.
Based on a panel discussion between Sudhish Singh, Head, O&M, L&T; and Atasi Das, Assistant Vice-President, GR Infraprojects Limited at a recent India Infrastructure conference
