Reduce, reuse, and recycle—the drivers of sustainable road construction

Sustainable road construction does not stop with reusing and recycling alone. It encompasses best practices to be followed in planning, design, execution, and maintenance of roads as well.

How do circular economy principles drive sustainable road construction in India?
The concept of sustainability revolves around three basic principles: reduce, reuse, and recycle!

“Reduce” in road construction refers to the optimal design of pavements without compromising strength, safety, and reliability. Techniques like soil stabilisation with cement, lime, fly ash, and bio-enzymes can help. Utilising industrial waste, such as fly ash, helps address the issue of waste disposal. Innovative materials, such as geosynthetics for pavement reinforcement, waste plastic in bitumen, crumb rubber-modified bitumen (CRMB), and industrial by-products like steel slag and copper slag, will also reduce overall material consumption and improve pavement performance.

The recently introduced micro-surfacing technique also offers sustainable pavement maintenance. “Reuse” in road construction refers to techniques such as full-depth reclamation (FDR), which is notable for its cost-effectiveness and faster construction, resulting in a 30–40 percent savings over conventional reconstruction. With “hot and cold recycling” for pavement construction, the approach is far superior in terms of sustainability, offering advantages such as material conservation, energy efficiency, lower carbon footprints, reduced life-cycle costs, and shorter construction times.

What best practices in planning, design, execution, and maintenance drive the long-term success of road projects?
Best practices begin with the preparation of a detailed project report (DPR), which includes thorough surveys and investigations. The tender documents and designs should be reviewed and proofread, with essential steps such as safety audits, to instil confidence in the thoroughness of the planning process. When formulating construction strategies, the use of high-performance materials, such as modified bitumen (PMB/CRMB), stone mastic asphalt (SMA), high-performance concrete (HPC), fibre-reinforced concrete, and recycled materials (RAP and plastic waste), should be considered. During the implementation stage, modern construction technologies such as sensor pavers, intelligent compactors, and slipform pavers should be deployed. It is essential to give attention to surface and subsurface drainage, as well as well-designed safety features, such as road camber, superelevation, appropriate site distances, crash barriers, pavement markings, and intelligent transportation systems (ITS). It is also essential to implement proper and adequate preventive, corrective, and periodic maintenance measures following timely safety and quality audits.

What methodologies must be undertaken during road construction to mitigate challenges related to the deterioration of asphalt roads?
The first step is selecting an asphalt of the appropriate grade. Asphalt should be selected based on climatic conditions and traffic loading, as guided by IRC 37:2018 and IRC SP:135-2022. Additionally, the use of modified bitumen, such as PMB or CRMB, is recommended for enhanced thermal resistance and durability. High-quality aggregates should also be appropriately selected to ensure strength and resistance to surface wear. The performance evaluation of the asphalt mix for critical parameters, such as fatigue cracking, rutting, and low-temperature cracking, should be undertaken. The most important aspect is to adhere to a strict quality control plan during the project’s implementation.

What are the key considerations to be adopted during road construction to ensure adequate drainage?
Both surface drainage and subsurface drainage need to be scrutinised. For efficient surface drainage, the following elements should be carefully examined: appropriate camber, side drains, catch drains, adequate longitudinal grade, and cross-drainage structures. The AASHTO Pavement Guide and IRC 37 recommend adequate subgrade drainage through the use of a granular subbase and a design drainage layer thickness determined based on anticipated infiltration and drainage time. The filter criteria must meet guidelines to prevent clogging. Special attention must be given to drainage of embankments and cut slopes. At the same time, the pavement design and drainage systems should be well integrated. Other parameters to consider include the moisture susceptibility of materials, the depth of the water table, and the permeability coefficients of each layer. Efficient operation and maintenance (O&M) is essential for the long-term functionality of drainage systems.

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