Seamless for endless possibilities: Durable concrete floors without expansion joints

Over the years, various techniques, including pre- or post-tensioning, have been developed to improve the structural physical properties of concrete. For concrete floors, it is mainly shrinkage, strain and temperature stresses or compression and bending loads that must be controlled to avoid cracks and ensure stability. SigmaSlab®, an innovative and revolutionary technique co-developed by Bekaert (Dramix®), now allows the realization of truly durable concrete floors without expansion joints.

Bart Wight, Dramix® Sales Engineer Netherlands: "The 'Sigma' in SigmaSlab® was not chosen by chance. After all, the Greek letter symbolizes both tension (lowercase) and sum (uppercase). This new story combines the familiar Dramix® steel fibers in concrete with CCL's post-tensioning system. Dramix® steel fibers are ideal for absorbing compressive and bending loads; CCL's post-tensioning strands, for their part, mitigate the effects of tensile stresses, including those caused by hydraulic shrinkage and temperature fluctuations. SigmaSlab® combines all the advantages of a passive reinforcement (steel fibers) with those of an active reinforcement (post-tensioning strands)."

Hendrik Thooft, Construction Technology & Value Solutions Manager at Bekaert/Dramix: "The whole is clearly greater than the sum of its parts here. After a long testing phase, which took place mainly in the USA (Virginia Tech University) and after some extremely successful pilot projects, it is clear that with SigmaSlab® a revolution has begun in the construction of concrete floors. Concrete floors with areas of 150 x 150 m without any expansion joints have become a reality. Confidence in SigmaSlab® is already particularly high, even in Belgium where Aertssen was the first to apply the concept."

The benefits of SigmaSlab® are on three levels, from the construction company, the end user and the environment. The absence of joints not only offers an aesthetic advantage, it also makes the maintenance of the floors easier and extends their lifetime. Pouring the floor is faster and this way of working allows to save up to 70% of steel per square meter. The floors can also be made thinner, requiring less concrete. Less steel and less concrete lead to a significant reduction in the ecological footprint thanks to a CO2 emission reduction of up to 25% per project. Because execution times are shorter, construction costs are also reduced significantly.

SigmaSlab® will be able to prove its added value mainly in three concrete situations: concrete floors on an elastic bed, concrete floors on foundation piles and storey floors. As for floors on an elastic bed (including concrete exterior pavements): with just the addition of Dramix® steel fibers, up to 40 m can be gone without an expansion joint. When combined with post-tensioning strands, the distance between joints is increased to 150 m.

For concrete floors on foundation piles, it comes down to absorbing the various loads and distributing them as a function of pile spacing. When these exceed 3 m, SigmaSlab® is the surest and cheapest solution at higher loads.

SigmaSlab® is already fully in line with contemporary architecture and design language, working primarily with slender structures and open spaces. Besides two large pilot projects in Germany, one project in Belgium and one in Mexico, the system is ready to be rolled out worldwide. Currently, a first SigmaSlab® floor is also being implemented in Trondheim, Norway.