*2.2. Microstructural Characterization*

The microstructural characteristics of the materials were also studied via 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR) at the age of 90 days. Solidstate 29Si MAS-NMR spectra were recorded using a Bruker Avance-400 pulse spectrometer. Spectra were recorded after irradiation of the samples with a π/2 (5-μs) pulse; the resonance frequency used was 79.5 MHz, (9.4 T magnetic field), and the spinning rate was 10 kHz. In order to avoid saturation effects, the recycle delay time was set at 10 s. All measurements were taken at room temperature with TMS (tetramethylsilane) as the external standard. The error in chemical shift values was estimated to be lower than 0.5 ppm. NMR spectra deconvolutions were performed using the DMFIT software [15]. Chemical shift (position of the line), intensity (integrated area), width (width at half-height), and line shape (Lorentzian or Gaussian) of the components were then deduced.

## *2.3. Immersion Test*

The samples for the study were manufactured using the materials specified above and were arranged as shown in Figure 1. For the development of the electrochemical tests, Cu/CuSO4 (sat) electrodes were used as external reference electrodes. The working electrode corresponds to a reference structural steel ASTM A706 commonly used in earthquakeresistant constructions, with a diameter of 1/8" and without any previous treatment.

**Figure 1.** Reinforced concrete used in determining the effect of porosity and its correlation with degradation: (**a**) sample; (**b**) schematic.

The samples with the reinforcing steel were immersed in a liquid solution saturated with 3.5% analytical sodium chloride (Panreac PA 131655.1211 NaCl-99.0%), and cycles of agitation of the liquid solution were carried out every 28 days. Due to the evaporation process that occurs, the solution was analyzed and stabilized to the original salt content in order to maintain the initial conditions. This solution then acts as the electrolyte of the electrochemical cell, which was located in a climate controlled environment at 20 ◦C with a relative humidity of 60%, where it was left to stand for 60 min after carrying out the connections of the assembly in order to avoid distortions during the measurements performed during testing.
