60,000 cubic metres of carefully tested concrete structures were used in Keilaniemi

In the Keilaniemi modernisation project in Espoo, Finland, cars will move from the Ring I main road to a 460-metre-long concrete tunnel. This will improve the area’s traffic connections and reduce the negative impacts that traffic has on residents. The tunnel between Tapiola and Keilaniemi, with its park covers and bridges, required tens of thousands of cubic metres of concrete. The quality of the concrete was controlled with a vast number of quality tests.

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The Ring I Keilaniemi project is one of Finland’s largest, particularly in terms of concrete volumes. Sweco’s experts have been heavily involved in the development of the area. In the last four years, more than 60,000 cubic metres were needed for the tunnel and its bridges, support walls and other infrastructure. Various types of concrete were used for the project.

“Concrete in the P20 strength class was sufficient for the warm and dry indoor spaces, while the vault structures and protective structures of the tunnel needed stronger concrete. The strongest concrete structures need to withstand difficult conditions, such as de-icing salts and freezing temperatures,” says Project Engineer Marianne Salo from SRV Infra Oy, the main contractor for Keilaniemi.

SRV was also in charge of concrete construction at shopping centre REDI’s rock site and the Länsimetro metro tunnel. What is special about Keilaniemi is that the concrete structures are combined with a variety of traffic control technology. The concrete was also poured to an extremely wide area.

“We couldn’t pour the concrete during rush hour, since the concrete trucks would have been stuck in traffic,” Salo says. “We always included a map with our orders so that the driver would know the right route and the right destination.”

The length of the Keilaniemi tunnel doubled

When testing the compression strength of the concrete, the project parties followed the rigorous quality control policies of the City of Espoo.

“Even though the regulations of the industry became stricter during the project, we didn’t need to change the quality control at Keilaniemi in any substantial way,” Salo says. A laboratory technician of Rudus, the concrete supplier for the project, carried out the air content measurements and samples for testing. “One sample of each cubic metre is required, but we took more: at least six samples per structure,” Salo says.

“On the busiest weeks, the concrete supplier delivered us 30 samples a week, which amounts to more than 100 tests a month!” says Sweco’s Tuomo Rimpiläinen, who was responsible for the concrete compression strength testing and reporting. During the project, 1,500 individual tests were carried out in total. This is an astounding number, considering that a typical construction site usually involves 10 to 40 tests.

The single largest sites at Keilaniemi were those of the tunnel’s support walls and the concrete cover. The tunnel was initially planned to be 200 metres long, but it ended up being nearly 500 metres long. Additional bridges were also built, and the period spent at the worksite lasted a year longer than planned.

“At the start of the project, we didn’t yet know the final number of concrete tests, but that wasn’t a problem in the end. We were flexible, and we were able to deliver the results and reports to the client during the same day,” Rimpiläinen says.

Sustainable urban construction that will endure for the next 100 years

As a result of the project, Keilaniemi has tunnel structures and infrastructure that will withstand the world’s changes for the next 100 years. At the same time, the tunnel frees up valuable space for sustainable urban construction, green areas and residential areas.

“Keilaniemi is one of our highest-profile projects and also an important calling card for us,” Salo says with pride. “The reports from Sweco’s testing services always arrived on time and as agreed.”