The entire DemoSATH is made of concrete. It is a concrete with a density of 1.85 tonnes per m3 (concrete usually has a density of 2.45). When the project started, the working formula was not yet available. SAITEC, the client, was working on the formula together with the Santander Civil Engineering School. Ferrovial has successfully achieved this formula which, in addition to achieving the objective of having a density of 1.85, achieves a resistance of between 45 and 50 megapascals, which is maintained from the concrete plant to the construction site – since the density is altered and rises during transport and pumping. The problem with low density concrete is that as the density goes down, pumping becomes more complicated.
Ferrovial’s commitment was to help achieve the concrete formula. It was a challenge to obtain a concrete with such demanding specifications of density, strength and consistency and that was pumpable. After months of tests, we were able to successfully achieve this formula which, in addition to achieving the objective of having a concrete with a low density of 1.85Tn/m3 , reached resistances of over 50 Mpa, with a liquid consistency, high impermeability and pumpability.
Lightweight concrete is a conventional concrete modified by the introduction of air into the mass to reduce the density to below 2,000 kg/m3, whereas conventional concretes have densities in the range of 2,200-2,600 kg/m3. Density reduction by inclusion of air means that lightweight concretes have significantly lower compressive strength than conventional concretes. Thus, the ACI 213R guide establishes a classification according to the density of lightweight concrete, which considers structural lightweight concrete to be those with a density between 1,300 kg/m3 and 1,900 kg/m3, with a strength of more than 17 MPa.
However, within the scope of the DemoSATH prototype project, the design needs imposed by the floating platform for wind turbines required the use of a high-strength lightweight concrete, with a density of less than 2,000 kg/m3 , and with a characteristic compressive strength of over 50 MPa, self-compacting and pumpable, which represented a real technological leap with respect to known lightweight concrete technology.
In this context, the works team set out to develop a new procedure for the manufacture and installation of lightweight concrete with the required performance, with the support of the Machinery Service to develop the working formula.