## 2 Experimental Program
### Accelerated Corrosion Test  
The accelerated corrosion of the carbon steel rebar was performed using the impressed current mode [38; 42; 43]. This type of method has been reported in numerous previous studies and has proved its effectiveness and relevance [7; 14; 17; 18; 19; 20; 21; 22]. Figure 2 presents the experimental setup. The current density between the rebar and the platinum mesh was controlled by a power supply (Agilent 6614C, Agilent Technologies, Les Ulis, France, 100 V, 0.5 A) where the positive and negative poles were, respectively, connected to the rebar and the mesh. The platinum mesh (275 mm long, 75 mm wide) was placed into a bottomless PVC tank glued (a cyanoacrylate-type mastic was applied) on the centre of the top face of the RC prisms (Figure 2). The length of rebar that is considered to be corroding is the length of the platinum mesh. Therefore, the surface area of the carbon steel rebar was equal to 172.8 cm\({}^{2}\). For each current density, the RC prisms were connected in series. For illustrative purposes, an example is shown in Figure 2a. Three days before starting the accelerated corrosion test, the PVC tanks were filled up with an alkaline and chloride solution composed of NaOH (1 g/L), KOH (4.65 g/L) and NaCl (30 g/L). The solution level was maintained constant by refilling the tanks daily. This allowed the prism to remain in a state of wetting, making it possible to lower the voltage needed to provide the impressed current. Chloride ions migrated from the solution to the rebar in two stages: firstly, by diffusion and secondly, by an electrical field. Three series of impressed current densities (50, 100 and 200 uA/cm\({}^{2}\) of surface of steel) were used to accelerate the corrosion of the rebar (Table 2). These three current densities are not chosen at random but according to the literature [7; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22]. Indeed, the current density \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & & & \multicolumn{4}{c}{**Aggregates**} & & **Cement** & **Water** \\ \hline
**Size (mm)** & 0/0.315 & 0.315/1 & 0.5/1 & 1/4 & 2/4 & 4/8 & 8/12 & 12.5/20 & & \\ \hline
**Composition** (kg/m\({}^{3}\)) & 149 & 277 & 180 & 170 & 57 & 324 & 265 & 473 & 275 & 192.5 \\ \hline \end{tabular}
\end{table} 
Table 1: Concrete mix composition. Figure 2: Accelerated corrosion setup: (**a**) RC prisms connected in series; (**b**) subcircuit involving a single RC prism; (**c**) cross-section view (T means top face and F means front face). of 100 \(\upmu\)A/cm\({}^{2}\) is frequently used in the literature by many authors [7; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22]. Some authors state that it corresponds to the highest corrosion current density recorded in existing RC structures [17; 30; 44]. Others say that this represents a reasonable value that enables the acceleration of the corrosion process, the achievement of a corrosion pattern similar to that obtained under natural corrosion and the prevention of excessive internal pressure within the concrete sample without altering the concrete and without compromising the reality of the corrosion products formed [4; 38; 45; 46]. The other two current densities, 50 and 200 \(\upmu\)A/cm\({}^{2}\), were chosen in order to analyse the effect of the current density and the exposure time on the corrosion-induced damage (thickness and distribution of corrosion products and cracks) for the same total charge. For further clarification, please refer to the definition provided in the final paragraph of this section.