Low-carbon concrete tested in Ropsten and Värtahamnen

To reduce the environmental impacts associated with the use of concrete, different concrete mixtures are currently being tested in Stockholm Royal Seaport, with certain components being replaced by slag. Two examples of these tests are the temporary pile deck for the Lidingö tram in conjunction with the construction of the bridge Lilla Lidingöbron at Ropsten, and the expansion of Saltkajen in Värtahamnen. Stockholm Royal Seaport will be able to evaluate the results of the various mixtures in building work on land and under water for several years.

Lilla Lidingöbron pilot project

Lilla Lidingöbron is the new link between the island of Lidingö and Stockholm. At the bridge abutment in Ropsten, the City Development Administration is responsible for a new pile deck that supports pedestrian and cycle paths and two tram tracks. Before all necessary investigations and planning and design is complete and the new station in Ropsten can be built, tram traffic between the existing station and the site of the new track on the bridge has been routed via a temporary pile deck. The idea is that the temporary pile deck will be used until the current station is demolished.

A key aspect of sustainability efforts in this project is to establish how the environmental impact of concrete can be reduced. Construction of the temporary pile deck is being used to test different concrete mixtures to evaluate how concrete can be made in more environmentally friendly and low-carbon ways, while maintaining all its necessary performance characteristics. This is done by replacing specific ingredients of cement with blast furnace Granular Blast Furnace Slag (GGBS). For the temporary pile deck, which will have a limited lifespan, different proportions of slag in different structural sections of the deck are being tested, reducing the proportion of cement to slag by 35, 50, and 65 per cent, respectively. Over a number of years, the performance of the various concrete mixtures will be monitored and results will be published.

The pilot project, which is also the subject of a university thesis, was initiated by the City Development Administration and Transport Administration, construction company Peab and concrete supplier Swerock.

Lilla Lidingöbron has been built by Lidingö municipality and on 11 October, the bridge was opened to pedestrian and bicycle traffic. In 2023, tram services will also start using the bridge as the old bridge is dismantled.

Development of low-carbon concrete at Saltkajen

Another project where low-carbon concrete will be tested and evaluated is the expansion of Saltkajen in Södra Värtan. Unlike the tests carried out with Lilla Lidingöbron, this concrete mixture is for use under water, so-called UV concrete. First thing will be laboratory tests followed by full-scale tests in water-filled containers to ensure quality standards. By using different amounts of slag, the carbon dioxide load can be reduced by 30 per cent. The fact that testing is carried out in situ at Saltkajen is, in part, due to a lack of experience in casting UV concrete in combination with slag admixtures. The project is expected to start in 2023.