Significantly reduced climate impact
Using a polymer-modified binder (PMB) that contains biogenic material increases the service life of a pavement while simultaneously reducing the climate impact.
An important aspect of the work to reduce a product’s environmental impact is to increase its service life. And if you can improve the opportunity for circularity, i.e. reusing or recycling the product, that is another benefit.
Both of these properties are characteristics of bitumen in road applications; in addition to the long service life, asphalt is 100% reusable.
“By adding polymers, you can further extend the service life of a road,” says Jenny-Ann Östlund, Nynas Bitumen Technology Manager. ”One downside is that a PMB in itself has a larger climate impact due to the relatively large contribution of the polymers to its carbon footprint. This is in a way compensated by the longer service life.”
To reduce the climate impact even further, Nynas has developed the Nypol RE range – PMBs that contain material with biogenic carbon, which compensates for the increased footprint from polymers without affecting the extended service life that they provide.
“Viewed over a life cycle perspective, that’s the whole service life of the product, this results in a significantly reduced climate impact,” confirms Jenny- Ann Östlund.
The use of biogenic material in the binder is aligned with the guidelines on which the construction group Skanska bases its work. By gradually reducing the climate impact from their asphalt products, they aim to be climate-neutral by 2045.
One important step in this direction was taken last autumn, when they installed a new pavement, with a total area of 35,000 m2, on Stockholmsvägen in Malmö, Sweden, using Nypol RE 73 on part of the surface. This is a section of road with both intense and heavy traffic, around 25,000 vehicles a day in one direction.
In addition to using PMB to increase the service life, the client, the City of Malmö, was interested in a solution with the smallest possible carbon footprint. This opened up an opportunity to test the new Nynas binder.
Before surfacing work started, Skanska conducted laboratory studies in order to assess and compare functional properties in the asphalt mixture made with Nypol RE with a reference using conventional PMB.
“We were unable to identify any differences between the two types,” says Kenneth Olsson, Skanska’s asphalt specialist. “The purpose of the test sections on Stockholmsvägen is to verify that the functional properties we see in the laboratory correspond with real traffic loading on the road.”
At the end of September, the paving team from Skanska was ready to start work. The existing asphalt was milled away and replaced by the new, polymer-modified surface. A shuttle buggy was used to make sure that the asphalt mixture maintained a consistent temperature. A homogenisation unit like this in front of the paver stirs the asphalt just before it is laid, producing an extremely fine surface structure.
“We were also able to confirm that the new binder flows more freely when discharging compared with a regular PMB, and that the asphalt mixture has really good workability when, for example, handlaying around gullies and manholes,” says Kenneth Olsson. “In conclusion, the project in Malmö is a good example of how we can work together in the industry to develop green products and reduce our climate impact.”