Session: Construction & Industrialization

Paper Number: 165243

165243 - Experimental Assessment of an Innovative Watertight Membrane for Chloride Ingress Prevention in Floating Offshore Wind Concrete Foundations 

Abstract: 

Concrete floating offshore wind foundations are known for being highly competitive and environmentally friendly structures while offering unrivaled local content during their construction. Part of these attractive characteristics originate from concrete being intrinsically highly durable material that is resistant to corrosion from seawater, hence dramatically reducing the need for costly maintenance compared to steel. Steel reinforcements positioned in the concrete structure must, however, be protected against corrosion potentially caused by chloride ions penetrating through the concrete cover. This protection is typically achieved through adopting sound design measures such as proper control of the crack width opening in service conditions. This usually relies on the use of high content of cement, high-density steel reinforcement bars and prestressing cables integrated in the concrete structure.

This presentation gives insights into running testing experiments aboard the 2MW Floatgen floating wind demonstrator offshore in France. These tests ultimately aim at qualifying cost-effective alternative means to protect concrete structures against corrosion, by demonstrating the performance of an innovative watertight membrane in preventing the penetration of chloride ions.

The experimental campaign discussed in the presentation was launched in summer 2024 to assess chloride ion penetration on the concrete foundation Floatgen, deployed off the coast of Le Croisic on the SEM-REV test site. This campaign aimed at measuring chloride ion penetration within core samples since Floatgen’s commissioning mid-2018, and at installing new experimental concrete samples to evaluate chloride ion penetration after 1 and 2 years of exposure. Both Floatgen-like concrete mix and a new low-carbon concrete mix are considered in the experiment. A watertight membrane is used on half of the samples to assess its potential in preventing chloride ion penetration, hence, any risk of steel reinforcement corrosion. Other complementary measurements are conducted to better understand concrete phase content and microstructure impacting the chloride ion penetration.

The chloride ion profile and diffusion coefficient were measured on both coated and non-coated concrete samples. No chloride ion contamination was found in coated concrete samples. In non-coated samples, a typical fast-decreasing chloride ion profile was measured. The diffusion coefficient associated with these non-coated concrete samples was found to be lower than the initial diffusion coefficient of this concrete, showing an expected decrease over time. The experiment is meant to last another 2 years. Results and findings to date indicate promising performance, as the watertight membrane still exhibits excellent properties after 7 years in harsh marine conditions.

Presenting Author: Nicolas Calvet BW Ideol

Presenting Author Biography: Dr. Nicolas Calvet works as a R&D Structural Engineer at BW Ideol specializing in solid mechanics and composite materials.

With a PhD in Solid Mechanics from Aix-Marseille University and over seven years of experience in mechanical design, structural analysis, and materials innovation, Dr. Calvet has contributed extensively to the advancement of engineering solutions in the renewable energy. During his PhD thesis, he developed an innovative solution of a composite material structure in a marine environment.

As a R&D Structural Engineer at BW Ideol, Dr. Calvet oversees multidisciplinary projects involving mechanical, structural, and material challenges. Dr. Calvet is actively involved in a consortium project, collaborating with researchers to improve the durability of concrete in marine environments.

Authors:

Nicolas Calvet BW Ideol
Walaa Farhat Ecole Centrale de Nantes, GeM
Magali Mouries BW Ideol
Thomas Soulard Open-C
Stéphanie Bonnet Université de Nantes, GeM
Emmanuel Roziere Ecole Centrale de Nantes, GeM