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New asphalt mix reduces carbon emissions by 5%


A new asphalt mix has been designed to reduce pavement rolling resistance without losing grip, which in turn reduces CO2 emissions by up to 5%, according to consultant Cowi.

The company said that by changing the mix to use smaller sized aggregate, PhD results indicated that fuel consumption could be reduced by 3% to 5% without undermining the road grip.

Cowi pavement specialist Huan Feng designed the new mix as part of his PhD project entitled ‘Modelling of asphalt mixture – A Discrete Element Method (DEM) to study the viscoelastic behaviour of asphalt mixture’.

“The project focuses on establishing a scientific background for novel pavement types and asset management solutions that minimise the rolling resistance for cars and trucks, and eventually attains the goal of reducing CO2 emission from the transportation sector,” said Feng.

He said that 25% of the energy consumption in Denmark was related to road transportation of people and goods, with one-third of that energy actually used to overcome the rolling resistance.

The research has been mathematically modelled and Feng said that this provided a time saving compared to lab tests and has already been applied to a project by Danish road authority Vejdirektoratet.

He explained that it would now take further studies to fully determine the viscoelastic behaviour of the asphalt when changing the mix design.

“A road consists of many layers and we have only focused on the top 30mm to 40mm, which is the strongest and most expensive part and it is this layer that decides how it feels to drive on the road,” explained Feng. “But when you change the mixture in the top layer it also has an impact on the lower layers, and this impact needs to be investigated as well before any final conclusions can be made.”

Cowi highways and airports international vice president Thomas Mejer added: “We are aiming at the most sustainable solutions and reducing CO₂ emissions while maintaining high performance and durability are key components to achieve that. In other words, the mathematical modelling holds a great potential for optimising the sustainability of new roads.” 

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