Coordinateurs du projet
Context
Many renewable energy production devices made of concrete are currently installed at sea. This material is generally reinforced with steel reinforcement that is prone to corrosion, particularly in a marine environment, due to the penetration of chloride ions, which alter the pH of the environment. The use of concrete for offshore structures therefore involves (i) defining a maintenance strategy to anticipate potential failures, (ii) assessing the remaining service life of structures, (iii) anticipating their recycling in the presence of chlorides (material polluted by chlorides), and (iv) optimizing future designs. Despite these challenges, only a few research projects have focused on concrete structures for use in floating offshore structures. Even fewer have addressed corrosion issues related to chloride ion contamination of concrete, while the effect of biocolonization on chloride ion penetration has not been studied, or at least not published. The primary objective of this project is to improve our understanding of these phenomena by developing algorithms to analyze measurements from sensors integrated into the structure (such as temperature, humidity, and resistivity) in order to map chlorides. The second objective is to map chlorides in a bio-colonized structure. The third is to develop a code for analyzing data from both in situ chloride measurements and accelerated laboratory tests to predict future penetration in a context of spatial variability. To validate these algorithms, in addition to the experimental results available in the bibliography, we will rely on experimental data collected by project members on several structures in the Loire region (TMDC5 port quay, concrete float, structural elements tested in the laboratory).
Instrumented beams installed on the float at the UN@PORT site at Nantes University
Scientific breakthroughs and innovation
Scientific breakthroughs revolve around five key challenges:
- proposing a resistivity model that takes into account any prior knowledge of resistivity field properties (spatial correlation, chloride front, etc.) while reducing the associated parameterization; optimizing the resolution algorithms to account for measurement errors and resistivity modeling errors.
- moving from resistivity mapping to chloride ion mapping. The relationship is not direct, and we will seek to identify a predictive model for chloride levels based on databases linking moisture content, chloride levels, and electrical resistivity.
- Identify the spatial viability of chloride ions as a function of depth and time, which has never been done before but is made possible by the resistivity sensor with the Trust-Chlorepredict approach developed by GeM.
- Analyze the role of biocolonization on chloride penetration over three years, particularly on spatial variability. We will draw on the results of the SIMAR project, which JUNIC is based on.
- Feed a chloride ion penetration prediction model based on accelerated coupled tests in tidal tanks and in-situ measurements.
Expected technical and economic impact
The project will mainly consist of developing algorithms for analyzing measurements from sensors whose technology and geometry have been disclosed in a publication following a patentability analysis by SATT. The economic impact is targeted in:
- the rationalization of monitoring: installing the right number of sensors in the right places in the structure in order to obtain the necessary and sufficient amount of information to optimize maintenance.
- the optimal design of floats (rationalization of the use of concrete with a high CO2 impact).
- Knowledge of the amount of concrete polluted by chlorides on a series of floats in a fleet in order to anticipate their recycling.
The partners MAREAL and SCE will contribute to the discussion and the direction of the project’s results in this regard.
Demonstrator
A demonstrator is available for viewing on request at the ESCOMar platform at GeM in Nantes and at the UN@PORT 1 and 2 test sites in La Turballe.
Perspectives
Operational instrumentation for a dock: response to a call for proposals. The project will serve as the basis for an Interreg Atlantic Area application, based on the Duratinet consortium.
Product patents
The project is based on the CHLOREDETECT patent, the SMARTCORE product, and R2PROBE.
Industrial benefits
For SCE’s Maritime Structures division, the aim is to deepen its knowledge in order to provide the best possible support to project owners, particularly in the context of offshore wind farms and substations, in the following areas:
- Recommendations, during the design phase, for concrete types that are resistant to corrosion caused by chloride ion penetration
- Predicting the residual life of structures with regard to chloride ion penetration.
- Defining a maintenance and repair strategy for offshore farms.
- Defining rehabilitation solutions for structures contaminated with chloride ions at the time of recycling.
Mareal innovates in fixed and floating foundation solutions designed to support offshore wind turbines, focusing particularly on concrete as a material suited to this industry, given its performance and durability in the marine environment, while also carefully considering environmental aspects and requirements for safety and longevity in service.
In this regard, the danger of chloride ions on reinforcements is identified and known, and the structural provisions for the bearing have an adverse effect on the dimensioning, requiring the size of exposed cracks to be limited and the thickness of the concrete cover to be increased.
This is why the digital twin project involving the mapping of chloride ions in concrete MRE structures is relevant, as it is crucial to gain a better understanding of the propagation of these ions, not only to ensure the suitability of the devices used, but also to understand how to control this propagation, while paving the way for optimization solutions.