Sustainable Practices: Use of advanced techniques and eco-friendly materials in road construction

With the increased scope of road construction, the road sector is focusing its attention on alternative construction materials and smart technologies for en­suring sustainable and quality output. To meet the government’s goal of carbon emissions reduction by 1 billion tonnes by 2030, green construction materials are being adopted. The Mi­nistry of Road Transport and Highways (MoRTH) has been instrumental in advocating and promoting the use of sustainable practi­c­es. The eastern peripheral expressway, the first smart and green highway in the country, has, for instance, deployed solar pumps for watering plants, and made arrangements for rainwater harvesting and drip irrigation for plants along the expressway.

Waste and indigenous materials

The use of naturally occurring construction ma­te­rial through quarrying degrades the environ­me­nt irrevocably while depleting the natural reserves. The use of alternative materials, whi­ch are the by-products of other industries or are locally available, can help address this iss­ue. Mi­xing of bitumen with shredded waste plas­tic, rubber, iron slag, fly ash, and construction and demolition waste has been helpful in mitigating this impact and reducing the cost of road construction.

MoRTH has shifted its focus to such green methods to reduce costs by 25 per cent while en­abling quality construction through finer te­chnological integration. About 250 metric tonnes of plastic waste has been used in 5-6 km of road projects as per latest statistics from projects done across the country, including Kochi, Mumbai, Kolkata, Maharashtra and Noida. Further, in December 2021, the Ministry of Defence announced the signing of an MoU between the National Highways Authority of India (NHAI) and the National Cadet Corps for reusing plastic waste collected by cadets, for the construction of roads across the country.

According to MoRTH, a forward-looking app­roach is required for the use of local material in eco-sensitive regions such as hilly areas, border areas and coastal areas. Materials such as jute and coir could be used for road strengthening purposes. Kerala has initiated the use of locally available materials like laterite stone in its rural road construction with the development of a new standard specification.

Geosynthetics

An eco-friendly alternative to conventional Portland cement concrete is geopolymer concrete. Its sustainable quality is that it has no requirement for water curing. Apart from this, it has high early strength, low shrinkage, freeze-thaw resistance, sulphate resistance and corrosion resistance. Geotextiles are a kind of geo­poly­mer concrete. They are permeable textile materials con­sisting of polypropylene or polyester. The road sector accounts for 70-80 per cent of geotextile usage. The government has been actively deploying geotextiles across road construction projects especially in the North­ea­st, which has high soil erosion. As of July 2022, the geotextile products of Maccaferri have been used in road projects in Assam to with­stand flo­ods and associated landslides.

Geogrids and geonets are two other compositions in this category. Two types of geogrids — uniaxial and biaxial geogrids — have been widely used across road projects in Assam, Bih­ar, Gujarat, Maharashtra, Tamil Nadu, Haryana, Uttar Pradesh, Andhra Pradesh, Rajasthan, Hi­ma­chal Pradesh, Karnataka and Chhattis­ga­rh, and in road strengthening projects in Mahara­shtra and Gujarat respectively. With its hardness properties, geonet sustains considerable loads and is used in landfills, foundation walls, me­thane roads and asphalt concrete pavements for erosion control and drainage.

Eco-friendly concrete

High performance concrete and ultra-high performance, fibre reinforced concrete (UHPFRC) have started to replace the conventional concrete and steel bars. As per MoRTH’s National Highway Precast Concrete Policy, at least 25 per cent precast components of the total concrete volume would be used in the design and construction of specific structures and bridges of national highways. NHAI plans to white-top the concrete on the Mumbai-Goa highway for ta­ckling the problem of potholes. This road stretch will also deploy UHPFRC technology for the construction of viaducts in the upcoming tunnel in Kashedi Ghat.

As per a study by the Indian Institute of Tech­nology Hyderabad, the hybrid fibre-reinfor­ced polymer strengthening technique has the potential to increase the service life of road in­fras­truc­ture by around 20 years at a marginal co­st. Su­p­p­or­ting the construction of bridges in India, MoRTH’s February 2022 circular emphasises the use of UHPFRC girders in bridges and structures. Recently, these girders were used in the Sole river bridge near Latur, Maharashtra. A few more bridges and viaducts spanning 50-72 me­tres have been approved for construction in the country. A bridge over the Ganga river parallel to JP Setu in Patna is also under similar planning.

Smart and electronic equipment

MoRTH and the Indian Construction Equipment Manufacturers’ Association released a Vision 2030 Plan of the Construction Equipment In­dustry in January 2021. It lays emphasis on the qu­ality and cost competitiveness of construction equipment. NHAI has taken the initiative to em­ploy sensor-based equipment for the construction of the Lucknow-Kanpur expressway. These sensors will ensure that profiling is performed according to the drawing without human intervention and provide a clear picture of the construction progress and quality. Given the positive feedback for the pilot project, NHAI plans to mandate the use of sensor-based equipment for all contractors.

To move towards sustainable equipment use, companies like Joseph Cyril Bamford, Vol­vo Construction Equipment Private Limited and Schwing Stetter are conducting feasibility studies for electronic versions of construction eq­uip­ment. Volvo has launched five electric models of three excavators and two loaders. Mean­while, Nexcharge, a joint venture between Exi­de industries and Leclanche, has started mass production of lithium-ion batteries for electric vehicles. Earthmovers and off-highway equipment companies are electrifying their forklifts, excavators and other equipment. Sany India has already started testing electric technologies for its excavators.

Tech-enabled technologies like telematics are being deployed in construction equipment. Telematics provides end-consumers with remote access and allows them to monitor eq­uipment data such as health, performance and mileage. Companies like Escorts, CASE, Action Construc­tion Equipment and Mahindra are planning a commercial launch of this technology in India.

New bridge construction technologies

A switch from multiple-pile foundation technology to monopile foundation technology has been planned by the Municipal Corporation of Gr­ea­ter Mumbai for the construction of pillars for bridges and interchanges of the coastal road project. A 10.58 km long project is to be constructed from Princess Street to Worli. This new technology will help reduce the project cost by Rs 120 million and the completion ti­me­line by three months.

New-generation modular bridges are also being slowly applied to a few projects because of the limitation with Bailey bridges. They are made of orthotropic steel decks, which distribute the loads better and are lighter than concrete decking. Moreover, they reduce 400-500 tonnes of dead load in a two-lane bridge of ab­o­ut 60 metres. In March 2022, the Border Roa­ds Organisation signed an MoU with Garden Rea­ch Shipbuilders and Engineers for the construction of 70 modular bridges of 27 double-lane class in the border areas.

Data Lake software

The enablement of digital platforms for the effective management of road projects is gathering pace. Data Lake software uses advanced analytics, which is cloud based and artificial intelligence powered. It is helping in transitioning from the manual system of project execution operations to NHAI’s online portal. Track­ing the project workflow and forecasting delays in timeline through the software helps in expediting decision-making. NHAI will be able to as­sess the financial impact of the alternative me­chanism in the project and avoid disputes due to delays in decision-making that lead to idling charges of equipment and manpower, shifting of utilities, etc. With its provision of project documentation, contractual decisions and appro­vals, the portal will minimise arbitration cases by providing conflict alerts.

The Data Lake dashboard also provides an accurate overview of the number of requests received for time extension and scope modification of the project. This digital system has already begun to yield positive outcomes, in addition to streamlining bill payment processes by tracking of submitted and paid bills.

Drones and LiDAR

In order to enhance transparency and ensure quality construction, NHAI mandated the use of drones for national highway projects at all stages in June 2021. All contractors and co­ncessionaires have to cover developments rela­ted to the project by carrying out monthly drone video recording and uploading comparative data on the Data Lake portal. The LiDAR (light detection and ranging) survey is also be­ing deployed for the preparation of detailed project reports and equipment-based testing. The two technologies have helped in optimising the planning pro­cess and enhancing the monitoring ability of contractors. The Vazhimukku-Kaliyikkavila stret­ch of Kerala’s six-lane highway has used LiDAR survey for its alignment and identification of the curve. According to the Kerala Road Fund Board, the technology will be used to detect any faults in the present alignment.

Other technologies

For developing further means of construction supervision, NHAI has decided to deploy the Network Survey Vehicle (NSV), which carries out a road condition survey on national highways. This has been made mandatory at the time of certifying the completion of the project, and every six months thereafter. As of August 2022, the road data of around 23,000 km of Tamil Nadu’s roads has been collected using NSV. There are 13 lasers for scanning above and below the surface of the road. This data in­cludes basic road data covering texture, roughness, geometry and assets like bridges and culverts. It enables planning future expenditure on roads by the officials. Furthermore, ground penetration radars, practices like bridge health monitoring, road asset management systems and bridge management systems are also be­ing scaled up. The adoption of building information modelling has streamlined the construction process and encouraged greater collaboration among all stakeholders. Geospatial technology is also increasingly becoming helpful in monitoring the condition of bridges remotely, especially in difficult terrain.

Future insights

The National Infrastructure Pipeline has projected a capital expenditure of Rs 111 trillion for the period 2019-25. The road sector has been allocated 19 per cent of funds in this budget. In the road equipment sector, loaders, motor grad­ers, compaction rollers and pavers (sensors and slipform) will be in demand in the future. Both technology and sustainability will play a significant role in the construction sector with the ado­p­tion of advanced solutions such as cloud-bas­ed collaboration, artificial intelligence, digital tw­i­ns, augmented reality, and ma­chine learning. The government is aiming to build 27 green ex­pre­ssways under the Bharat­malaPariyojana by 2026-27. However, the road sector has the maximum number of delayed projects, with delays in 300 out of 825 projects. In order to resolve the issue of project delays, the Bhoomi Rashi portal developed by MoRTH for digitalising the land acquisition process for NHAI will help in reducing the time period and increasing transparency in the process. The reduction of the goods and services tax rate to 18 per cent from 24 per cent for certain construction materials is also expected to give a forward push to the industry.

Moreover, NHAI provides the choice of adoption of these green materials and innovative technologies to the concessionaires and contractors. While there will be no revision in contract prices or transfer of cost reduction benefits to NHAI, the decision of using them lies with the contractors. This flexibility along with the ex­pan­ding market of green materials and equipment will promote sustainability and drive digital ad­vancement in the road industry.