sustainable road building

Research and development for sustainable road building is fast becoming a priority globally in a bid to reduce environmental impact.

Some newer methods and technologies also reduce the on-going cost of maintenance.

Recently, South Africa constructed its first sustainable road in Jeffreys Bay. The so-called plastic road uses a combination of tar and recycled plastic to create a longer-lasting and more cost-effective road surface.

What are sustainable roads?

A sustainable road is one that’s built in a way that reduces emissions and the use of water, energy and virgin materials during the construction process.

It has a lower impact on the surrounding environment and a longer lifespan, which reduces the need for future construction and maintenance.

Warm-mix asphalt for highways

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.

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.

Bio-binders for road construction

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. Studies are being conducted to test the viability of using the by-products of the microalgae industry as a bio-binder.

Using recycled materials in road construction

The asphalt industry has used recycled waste such as steel slag, glass and fly ash in road construction for many years. More recently, plastic has been incorporated, as seen in the Jeffreys Bay road.

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.

Other sustainable road construction practices

Making construction green generally also affects how sustainable a road will be. Many construction companies have incorporated green policies to reduce their consumption and impact.

Road construction projects can be made more sustainable by:

  • recycling, repurposing or reusing materials
  • using more eco-friendly and less toxic materials in construction
  • using local materials
  • reducing water wastage and incorporating water-wise systems
  • using energy-saving lighting options
  • educating the construction crew on eco-friendly practices
  • reducing the use of paper and unnecessary printing on-site
  • using reconditioned construction equipment.

Green road rating systems

Many countries have or are busy developing road-rating systems to assess whether a road is sustainable.

In the United States, Washington University has a tool called Greenroads and existing rating tools for buildings have been diversified to include road construction.

In South Africa, the Sustainable Roads Forum is developing a rating system for sustainable best practices in road construction focusing on planning, design and construction. It will also consider the socio-economic impact of road projects.

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