Tough demands on durability

The port in Piteå has has been expanded in stages since 2012. This expansion is a direct consequence of an increased demand for intermodal transport solutions from manufacturers of paper, sawn timber products and biofuels. Another driver is the deliveries of components to Europe’s biggest wind farm just to the west of the city, which will be comprised of 1,100 wind turbines when completed.

The third stage of the port’s expansion, which was completed in November 2020, saw the creation of additional terminal space both on land and through land reclamation measures. 500,000 tonnes of soil and rock masses were used for the filling process. The total cost of the project is 20 million EUR and is partly financed by the European Regional Development Fund.

Paving work was carried out by the construction company NCC over an intensive month last autumn.

Our role in the project was that of a subcontractor to NYAB, which has the turnkey contract, to assume responsibility for hardening and asphalting the new surfaces. We also discussed appropriate paving options in consultation with the client,” says Linus Gustafsson, contracting engineer at NCC Industry.

The choice of surface was in turn informed by what is to be transported and stored on the different surfaces, and what loads this involves.

On a relatively large part, where the area of application has loads similar to a normal road, we laid a conventional surface in two layers: approximately 50 mm base course (AG 22 100/150) and 40 mm surface course (ABT16 70/100).”

On surfaces where the stresses are significantly greater, they chose instead a pavement in three layers, with Nypol 73 in the binder course. Nypol 73 is a polymer modified binder (PMB 40/100–75) with especially good resistance to permanent deformation and crack formation.

“With the binder layer, which is also around 50 mm, it means that the thickness of the pavement is around 140 mm at the most. In total, we’ve asphalted an area of 55,000 m2, which corresponds to about 15,000 tonnes of asphalt,” explains Linus Gustafsson.

A relatively hard bitumen is usually used in ports. This is due not only to high axle loads, but also the fact that the support legs of containers sink down into a conventional surface. The challenge in this project has been to choose the right mix design to meet the strict demands, primarily for water sensitivity, rigidity and stability.

Another challenge was the weather, in view of the port’s location in Northern Sweden.

“During the last week we had 30 cm of snow overnight, which forced us to stop work. But after a few days the temperature rose again, so we could continue as planned.”

At the same time, Linus Gustafsson emphasises that it was in many ways a straightforward project, if you compare it with asphalting a road.

“With it being a totally new area that had not yet been commissioned, work proceeded without any major restrictions. As a contractor, it’s not often that you can access the work area without needing to consider traffic or other external factors.”

One important aspect for both client and contractor was to work with as much consideration to environmental impacts as possible. The asphalt was delivered from NCC’s stationary plant in Piteå, which minimised transport operations. The asphalt plant also has stringent environmental targets when it comes to how the mass is heated, as well as for manufacturing temperature and the use of recycled asphalt.

“The asphalt we used in the port was manufactured in accordance with our Green Asphalt* concept. For this project, it’s resulted in our being able to reduce emissions of CO2 equivalents by more than 60 % compared with a traditional manufacturing method,” concludes Linus Gustafsson.

* Green Asphalt is NCC’s method of producing asphalt with the least possible environmental impact, with a focus on reducing the use of fossil fuels, increasing energy efficiency and saving natural resources.