Steering towards sustainable roadbuilding

As towns and cities expand their infrastructure, the demand for better transportation grows. Whilst roadbuilding is certainly not on the list as one of the most sustainable sectors of construction – largely due to the negative impact the production of asphalt has on the environment – changes are being made in the industry to ensure it is working towards an environmentally conscious future.

Climate agreements and stringent regulations issued by governments and authorities worldwide are posing increased challenges for the asphalt industry concerning reducing greenhouse gases, such as CO2.

Many markets are phasing out coal as a fuel, while systems running on oil are subject to these regulations and restrictions says Benninghoven. In moves to work toward a more sustainable future, Benninghoven technologies have enhanced their Evo Jet multi-fuel burners, which can use renewable fuels such as biomass to liquid (BtL) and wood dust, in addition to both having a carbon neutral footprint.

Owners of asphalt mixing plants need to be conscious of driving down emissions to help secure the future of the plant site. Changing from oil or coal dust to gas is a major step says Germany-based Benninghoven – the use of natural gas or liquid gas already halves the CO2 emissions.

Benninghoven’s Evo Jet wood dust burner allows wood dust to be used in asphalt mixing plants. Engineers at Benninghoven are said to have identified the ideal particle size of the wood dust, which is produced from scrap wood and wood waste.

The fuels of the future, wood dust and biomass to liquid, are attractive when it comes to their availability, as fossil fuels are not only limited but are becoming increasingly more difficult to produce. Benninghoven says that this makes it even more important that plant owners use the right technologies to be prepared for the future by using alternative fuels.

Benninghoven is working towards carbon neutral fuels (Photo: Wirtgen)

Lowering emissions has driven machine development in recent years, and this has been a key focus for Benninghoven.

Among the company’s advances in the application of low-temperature asphalt, which although not new, has become the focus of road construction authorities today. The demand for balancing CO₂ levels, conserving resources, and reducing energy are driving innovation and asking companies across the sector to develop their capabilities.

It was formally requested in August 2021 by National Highways that everyone involved in the construction and maintenance of the strategic road network, particularly designers and main contractors, use low-temperature asphalt as their default surfacing material to help achieve net zero.

Low-temperature asphalt is a mixture that requires a production temperature between 110° and 130°. Hot asphalts, on the other hand, are produced at a temperature range between 140° and 180°, although 160° with hot bitumen as a binder is most common. The advantage is that the production and the processing of low-temperature blends can be conducted conventionally.

According to the German Asphalt Association, a temperature reduction of just 30 °C saves 0.9 litres of fuel oil (or equivalent fuel) per ton of finished asphalt; a daily production of 2,000 tons of mixture thus saves 1,800 litres of oil or up to three-quarters of the annual energy consumption for heating a house – the reduction in CO₂ emissions is 6,000kg per day.

Setting limits

Whilst the products and materials used in road construction are adopting new techniques that will reduce the impact we have on the environment, local authorities across the globe are beginning to impose limits on CO₂ emissions and on some occasions make them part of the tender requirements.

Vinci Autoroutes recently completed a 24km project on the Western Strasbourg bypass in France, with investments of €561 million – of this total, €130 million was spent on environmental integration.

To offset the negative environmental impact of its construction, 1,315 hectares of land were subject to environmental offsetting measures to allow biodiversity to flourish. The area is approximately four times the area covered by the road, and the bypass itself includes 130 passes that allow safe crossing for wildlife.

Driven by their own corporate social responsibility policies, as well as broader legislative requirements, sustainability is now forming a key part of the selection process for Altrad RMD Kwikform.

Martyn Henry, UK export manager at Altrad RMD Kwikform, says, “Customers are now demanding more of their temporary works’ solutions provider in terms of cost efficiencies, environmentally-responsible material selection and a reduction in preventable waste – in terms of wasted labour and material costs.

“On road bridges, all temporary works’ components are manufactured from either steel or aluminium, so once their lifecycle is over through damage or wear and tear, they can be recycled.”

Government and authority-set regulations are causing many companies to evaluate the materials they are using and how they can reduce the impact they have on the environment in roadbuilding projects. Altrad RMD Kwikform has made the switch from using plywood, for decking panels, to Alkus.

ARMDK Alkus panels are solid plastic formwork panels made from aluminium reinforced polypropylene and are said to enable up to 1,500 uses with just one panel.

This change is due to Alkus lasting longer and being better for the environment, in addition to eliminating the use of plywood that is impregnated with chemicals. The company says that Alkus is also less wasteful, as the decking is reused and not scrapped as the plywood was previously.

Overcoming challenges in roadbuilding

Raman Ojha, global head of Shell Construction and Road, realises that there are several challenges when it comes to making roadbuilding sustainable, he says, “There are multiple challenges to decarbonising roadbuilding, the most noticeable being the fragmented nature of the industry, which is why it will take collaboration across the entire value chain to overcome them. A combination of technology, low-carbon solutions, and supportive regulation can accelerate progress to net-zero.”

Raman Ojha, global head of Shell Construction and Road (Photo: Shell)

Shell has recently developed Shell Construction and Road, an integrated sector team collaborating with customers to develop a tailored portfolio of low carbon and circular solutions to help solve decarbonisation challenges and meet the industry’s sustainability goals.

“We don’t have all the answers ready,” says Ojha. “But by using a customer-backed approach we are continuously working towards uncovering new decarbonisation solutions in construction.”

Ojha believes that lowering demand for virgin resources through design and process optimisation and increasing closed-loop circularity for materials must play a key role in decarbonising construction.

He adds, “For example, asphalt is already one of the world’s most recycled materials, and the increased use of Reclaimed Asphalt Pavement exemplifies the benefits of increasing circularity for the industry.

“Recycling asphalt helps to conserve resources - the National Asphalt Paving Association has estimated that nearly US$2 billion (€195 million) in US taxpayer dollars are saved each year using recycled pavement in infrastructure in the country.”

Dura Products, a UK-based manufacturer of sustainable kerb alternatives, also agrees that employing a circular approach to the design of roadbuilding is the way forward. Steve Bennett, managing director of Dura Products says, “The company has recognised the collective need of the roadbuilding industry to reduce its reliance on new materials, increase the end-of-life potential of products, and seek out a more sustainable future.

“For nearly 20 years, we have demonstrated that green roadbuilding is a reality, and we are proud that demand, in response to increasingly eco-conscious consumers, government legislation and a general desire to protect our planet, is growing.”

A division of Bauer Resources, Bauer Environment, has recently been working on a project that not only makes a sustainable contribution to a clean environment but is in line with the circular economy.

Gravel excavation pit in Kirchheim near Munich (Photo: Bauer)

In Kirchheim, Germany, tons of gravel were excavated during the construction of a pit for a new residential area, which is now being reused for concrete production. A total of 38,000 m3 was excavated and disposed of with a resulting 33,000 m3 of gravel transported to nearby gravel works to be processed into concrete.

In Germany alone, it is said that around 27.5 million tons of concrete are produced every year. Bauer believes that if only a small part of it were produced from recycled gravel, then concrete production would be more sustainable.

Closing the loops

Innovation can play a vital role in closing the loops in a circular economy. Shell’s Ojha believes that it is important to cut the number of virgin resources going into newly produced asphalt. “Our product, Shell Bitumen LT R, is made using an LT additive from plastic waste’s chemical conversion. It is just one clear demonstration of how innovation can be put into practice to help close loops in a circular economy.”

Reducing emissions from roadbuilding can also be done by using lower mixing temperatures says Ojha. This can be achieved by using binders with special additives, which results in reduced CO₂ emissions during mixing.

Ojha says, “Our specially designed binder, Shell Low-Temperature Bitumen, works at production temperatures up to 30°C lower than conventional asphalt, reducing the emissions produced during the heating and mixing of asphalt and also helping to control the costs of energy consumption.

“Other ways of making roadbuilding more sustainable come from the use of biogenic materials. Our latest product, Shell Bitumen CarbonSink, which was used in the UK to produce the market’s first biogenic asphalt and has recently been assessed successfully in France too, locks carbon into the road, effectively turning it into a ‘carbon sink’. The carbon remains locked in the road when it is recycled as well, avoiding the carbon’s emission into the atmosphere.”

Contractors, manufacturers and authorities are willing to play their part in making sustainable alternatives to roadbuilding. As innovation continues to grow within the industry there is likely to be continued developments in the technology and processes we currently know.

Breedon partners with Nynas on a low carbon surface course

Breedon and Nynas have announced the first use of a low carbon surface course using a polymer modified bitumen (PMB) containing a biogenic component.

The PMB was used on a car park project in Nottinghamshire (Photo: Adobe Stock)

The binder is said to have been specifically designed to extend the useful life of asphalt and reduce the service life carbon footprint. Breedon says that this PMB, containing a biogenic component from Nynas, reduces the carbon footprint of the binder by up to 60% when compared to non-biogenic binders.

Breedon, working in partnership with Nynas, became the first to trial a PMB containing biogenic material in the UK when they chose Nypol RE 103 for a car park in Nottinghamshire – the typical tight turning circles and heavy abrasion demanded a high-performance asphalt.

“We are proud to be the first asphalt manufacturer and contractor in the UK to produce and lay an asphalt surface course using a polymer modified bitumen containing a biogenic component,” says Tony Wilson, technical manager GB at Breedon.

“The properties of the asphalt and test results demonstrate there is no difference in performance between Nypol RE 103, the PMB with biogenic material, and Nypol 103.

“This new binder is a major change for the industry, with the ability to now offer a PMB performing asphalt with a lower CO2 footprint, which will significantly reduce a pavement’s environmental impact.”