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The innovative refinement and in-depth knowledge of Steel Fibre Reinforced Concrete (SFRC) gives COWI a head start in tunnel projects around the world. The unique material is optimal for segmental linings for bored tunnels, it is highly durable and it leads to significantly lower CO₂ emissions compared to traditional reinforced concrete.
Traditional practices in the concrete construction industry depend on environmentally demanding processes, such as mass consumption of energy and raw materials, and they contribute significantly to global CO2 emissions.
Fortunately, there are alternatives. COWI has developed and refined a unique material, SFRC, which is among the greenest reinforced concretes ever produced when used together with a special concrete mix consisting of flash and slag.
"Our work with SFCR has started to pick up speed in the last five years, and we have managed to bring down CO₂ emissions and increase durability even further due to a new and refined mix ratio, which has been used on the Doha Metro Red line and Green line project. It is a differentiator in winning tunnel projects around the world," explains Technical Director Carola Edvardsen, who heads the development and refinement of Steel Fibre Reinforced Concrete (SFRC) in COWI.
Due to the good results with SFCR, many contractors have it as a requirement in their bid material. Although some competitors are now learning and offering the technique, COWI has a head start, particularly in the Middle East, says Carola Edvardsen.
"The SFCR ingredients act differently in different parts of the world, and it takes time to gain this particular knowledge. As a consequence, we have competitors who have won contracts and end up calling us to handle the SFCR requirements, because they don't have the necessary knowledge."
Steel consumption is drastically reduced in SFRC, and the improved performance of SFRC allows reduced thickness of tunnel segments. This means that far less concrete is required. Finally, as steel fibres are compatible with all forms of supplementary cementitious materials, CO₂ neutral by-products from other industries such as slag, fly ash, and silica fume reduce the demand for cement even more. Consequently, CO2 emissions from the production of SFRC are reduced by 60-70% compared to traditional reinforced concrete.
"The demand for sustainable and durable solutions is rising, and we are in a good position to use our expertise within SFCR to enter new, strategic markets, e.g. in Southeast Asia," says Carola Edvardsen.
SFRC is an ideal material for bored tunnels with lengthy service life requirements of 100 years or more and with exposure to the harshest environmental conditions.
Advantages of SFRC structures, compared to conventional reinforced concrete, include significantly reduced construction costs and time, an intelligent and sustainable use of limited resources, top structural performance with reduced cross-sectional dimensions and inherent immunity to degradation mechanisms. The material provides approximately 5 to 10 times the resistance to chloride-induced corrosion compared to traditional reinforced concrete.
Beyond application for bored tunnels, COWI's specialists have used SFRC for high warehouse spaces, including Carlsberg's brewery in Fredericia, Denmark, shafts for the Abu Hamour ground and storm water tunnel, and in the design of a state-of-the-art demonstration road bridge in Denmark. Also, COWI is preparing a tender for the biggest storm water tunnel ever build in the Middle East. The tunnel is called Dubai Storm water Tunnel and the solution proposed utilises SFRC for the tunnels and shafts.
Carola Edvardsen Technical Directorcle@cowi.com