Low-temperature asphalt reduces energy consumption and emissions

Finnish National Road 8 in Turku is being surfaced with low-emission asphalt. We surfaced part of the motorway using low-temperature asphalt.

Sustainable development is central to Lemminkäinen’s operations. This in practice takes the form of, for instance, asphalts that are easier on the environment. In this area we are forerunners. In producing reclaimed asphalt we use old asphalt surfacing. We also invest in product development of low-temperature asphalt, which we have been working on for well over a decade now. Our first trial of low-temperature asphalt was done in Pori in 2003.

Now we’re surfacing Finnish National Road 8 in Turku with low-temperature asphalt at the start of the motorway - that is, at the Naantali expressway end. The paving of this stretch is part of the City of Turku’s pilot project to investigate the possibility of reducing emissions through more ecological types of surfacing.

“We are aiming at carbon neutrality by 2040, and we believe that using low-emission asphalt will help us to reach this goal,” explains Juhani Tirkkonen from the Public Utility Property Management department of the City of Turku.

Environmentally friendly surfacing through flotation technique

We did two stretches of the Turku motorway, one of 500 metres and the other of 4.5 kilometres. In both cases the surfacing thickness was four centimetres. That came to a total of around 450,000 tonnes of asphalt, which is about a hundred kilos per cubic metre.

For production of low-temperature asphalt we use the flotation technique, which we have been developing for 30 years now. Flotation makes the asphalt’s binding substance, bitumen, more fluid. This helps in making the mass more workable,” explains Lemminkäinen´s Research Director Lars Forstén.

Traditional asphalt manufacturing consumes a vast amount of energy, because the asphalt mass is worked in a temperature range of 140–180 degrees. Below that the mass becomes too stiff, making spreading and compacting very difficult.

“With the aid of the flotation technique we are able to handle the asphalt mass at a temperature that’s 20–30 degrees below that of the traditional method. This also reduces the amount of fuel consumed for heating in asphalt production,” Forstén adds.

A new technique, but asphalt properties remain the same

The part of the road selected for the  trial surfacing is very busy, which makes highly durable asphalt essential. Drivers will notice no difference at all between traditional and low-temperature asphalt.  Wear and ridging of the road surface will be monitored closely using laboratory tests and visual inspections.

“We’ll see whether the material is suitable for a tough urban environment. If the results are good, we expect to be able to increase the use of low-emission asphalt in our surfacing projects. Lemminkäinen has been the City of Turku’s asphalting contractor for a long time now. We’ve developed a very good working relationship,” says Tirkkonen.

The pilot surfacing was done by a team of seven. In the warm weather it’s more pleasant to work with low-temperature asphalt, since it doesn’t heat the surrounding air as much as traditional asphalt. With less steam and vapours produced by the asphalt mass, it also makes our working conditions that much easier,” says Area Manager Ville-Veikko Jäppilä.