Steel fiber-reinforced slag-based concretes for floats of FOWTs – The case of a slab as a preliminary approach: design, durability under chloride exposure and Life Cycle Assessment

Abstract

Concrete Floating wind turbine is a solution of the future for Marine Renewable Energies (MRE). The B2FE project, i.e., steel fiber-reinforced concrete (SFRC) for wind turbine floats, aims at developing and characterizing a slag-based concrete (low-carbon concrete) reinforced with steel fibers (slag-based SFRC). Four concrete formulations composed of 50 % CEM I and 50 % blast furnace slag, including fiber contents of 0 (i.e., no fiber), 20, 40 and 60 kg.m⁻³, are studied. A simplified case study is investigated by considering a slab under the same exposure conditions as a FOWT. Considering given mechanical requirements (distributed load of 100 kPa, i.e. 10 t.m⁻²), the dimensioning of the slab is carried out with, on one hand, the slag-based RC solution (no fiber) and on the other hand, the three SFRC formulations (no rebar). Compared to steel bar reinforcements, it appears that steel fibers can provide similar mechanical properties with fewer concrete or steel which is a very interesting result. Then, knowing the physicochemical properties of the materials, simulations of chloride ions transport in the slab subjected to sea water tidal conditions (known as much "aggressive" as splashing) are performed to estimate the service life of these solutions: they appear to be around 30 years, which meet the expectations. Finally, a cradle-to-gate Life Cycle Analysis (LCA) demonstrates a clear advantage of fiber-reinforced formulations, by reducing carbon footprint and other indicators of environmental impacts. In terms of service life and carbon footprint, an innovative cross-analysis leads to an optimal steel fiber content of 40 kg.m⁻³.