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Undoubtedly, the road infrastructure provides basis for economic development of a country. But the environmental consequences cannot be overlooked during the construction of roads. The conventional technologies of road construction require high amounts of energy and tend to create environmental pollution in terms of noise and air and also prove to be unsafe to workers and their health. During road construction, ecosystems are altered, wildlife is affected, trees are cut, construction materials are mined and waste materials are disposed off to the environment. On one side, roads are needed for our overall development, but on the other side, clear air and water is also required, which originate from the same areas being damaged by roads. So, there is a need to maintain a balance between the two sides. The solution lies in adopting the green and sustainable methods for road construction.

Sustainable development is meant to include and balance social, economic, and environmental (and increasingly climate change) needs and benefits. A sustainable road construction should satisfy lifecycle functional requirements of societal development and economic growth while reducing negative impacts to the environment and consumption of natural resources.

For a road or highway project to be sustainable it should offer a series of benefits. Among them: it should reduce money spent on combustibles, and limit as much as possible any maintenance needs and environmental impact. It should also guarantee the longest possible life for the infrastructure, and once it does become obsolete, its remains should be able to be recycled. And above all, it should comply with a series of requirements to reduce as much as possible the energy it consumes.

During road construction, it is usually a better option to use locally available construction materials (as long as they meet the specification requirements), as well as local resources, labour, and skills. Using local materials can be cost-effective and can minimize the air, noise, and dust pollution created by hauling materials from long distances.

Using innovative products and processes can also improve road construction sustainability. This involves using alternative materials and processes, using high-performance and value-added products, minimizing the use of natural resources, minimizing waste, recycling, reusing, and optimizing economic resources. Further, improving existing practices such as using warm mixed asphalt rather than traditional hot asphalt mixes or using alternative materials for pavement construction where appropriate (such as biopolymers or biobinders) can eliminate the use of hazardous substances and reduce greenhouse gas emissions as well as reduce energy consumption.

Recycling materials is a great way to reduce the amount of waste going into landfills and reduce the need for new resources. Recycling also reduces the amount of energy needed to produce new materials. The road construction industry has used recycled waste such as steel slag, glass and fly ash in road construction for many years and more recently, plastic has been incorporated. Crumb rubber, which comes from old tyres, is often used to give bitumen more elasticity. This results in a road that’s more flexible and resistant to cracks and potholes. It can also be used to create a sprayable road seal.

The use of Reclaimed Asphalt Pavement (RAP) in road construction has become more common over the last few years. Reclaimed asphalt pavement (RAP) materials contains valuable asphalt binder and aggregate. Large quantities of reclaimed asphalt pavement materials are produced during highway maintenance and construction. RAP is a useful alternative to virgin materials because it reduces the need to use virgin aggregate, which is scarce commodity in many areas of the globe. It also reduces the amount of costly new asphalt binder required in the production of asphalt paving mixtures. RAP recycling also tackles the issues of material storage and disposal of reclaimed asphalt material generated from pavement construction. Further, energy savings can also be done through the use of RAP in roadway construction by reducing the processing and transport of virgin aggregate.

To reduce the level of energy consumption, warm-mix asphalt (WMA) can be used to replace hot-mix asphalt (HMA). Warm-mix asphalt (WMA) is produced at a temperature up to 50°C cooler than traditional hot-mix asphalt (HMA). This means less energy is needed to heat the asphalt mix and less fuel is consumed. Besides the fact that WMA is produced at a lower temperature, it also induces great benefits such as an improvement of working conditions (less exposure to heat and fumes) and asphalt compaction, reduction of paving cost and longer hauling. WMA also reduces production time because it cools faster and is easier to compact. This reduces the cost of construction and means less time is spent on-site, which lowers the impact on the environment.

One of the options which would also allow to generate savings in energy and production costs is the use of “Bio-binders” as materials for sustainable asphalt pavements. Bio-binders – also known as biopolymer- come from natural resources and are fully bio degradable. They are rather cost effective and show good thermal stability. Bio-binders are organic alternatives to bitumen, which acts as a binder. They don’t replace bitumen but are blended with it to make a bio-modified binder. Alternate binders have good moisture resistance and age well, which extends the road’s lifespan. These bio-binders are usually made from products like vegetable oil (palm, soybean, linseed) and swine waste.

The stabilization of pavement by mechanical or chemical stabilisation methods has proved to be a successful and reliable technique to increase the performance of pavement materials and prolong the service life of a pavement structure. The stabilization of subgrade, granular sub-base, and base layers using conventional or commercial binders decreases the thickness of pavement layers compared to conventional pavement composition, thereby reducing consumption of soil and crushed aggregates. Along with lime, cement, Fly ash or coal ash, bituminous materials such as coal tar, bituminous emulsions, foamed bitumen and cutback bitumen are widely used for road stabilisation.

There are also other sustainable methods like Rubblization of Deteriorated Concrete Pavements, Cold Mix Asphalt Technology, Foamed Asphalt Technology etc. Utilisation of electric or hybrid construction vehicles or low polluting plant, equipment and vehicle also contributes to sustainable road construction.