## 3 Results
### Fourier Transform Infrared Spectroscopy  
According to previous studies [56; 57; 58], specific absorption bands can be associated with certain compounds. Portlandite, or Ca(OH)\({}_{2}\), is typically found around 3642 cm\({}^{-1}\), attributed to O-H stretching. The S-O bond (sulfate phases) stretch from gypsum, ettrinigite, and monosulfoaluminates is indicated at 1102 cm\({}^{-1}\). Ettrinigite, in particular, produces a band at 610 cm\({}^{-1}\) corresponding to the S-O stretch. Water can be detected by the broad band at 3373 cm\({}^{-1}\). Gypsum generates a band at 1680 cm\({}^{-1}\), attributed to O-H stretching. The presence of calcite and [PERSON]'s salt can be identified by the band at 1440 cm\({}^{-1}\), which indicates C-O stretch. The SiO\({}_{4}\) stretch, observed around 967 cm\({}^{-1}\), corresponds to C-S-H, calcium aluminate hydrates, and H\({}_{2}\)O. Additionally, [PERSON]'s salt can be identified around 810 cm\({}^{-1}\), which refers to the stretching vibration of the Al-O bond in the material. Our FTIR test results are shown in Figure 6.  
The analysis of FTIR spectra provided valuable insights into the chemical reactions occurring in the different mixes under various exposure conditions. As illustrated in Figure 6, the peak at 3642 cm\({}^{-1}\), indicative of portlandite, showed that its presence diminished over time due to exposure to chloride ions. In Mix2, portlandite disappeared after 25 days, while in Mix3 and Mix4, it vanished after 11 days and 5 days of exposure, respectively. Although the TGA did not detect this compound in Mix 3 and Mix 4, FTIR analysis revealed its presence in those mixes. This might be due to its presence in low quantities. In the case of chloride exposure (EXP1), the presence of [PERSON]'s salt was detected from the first day, explaining the consumption of portlandite in this exposure condition. Notably, the peak at 810 cm\({}^{-1}\), representing [PERSON]'s salt, was absent when sulfate was present along with chloride (EXP3) (refer to Figure 7). This observation aligns with previous studies [11; 25] that have demonstrated the instability of [PERSON]'s salt in the presence of sulfate. This phenomenon was attributed to the substitution of chloride ions (Cl\({}^{-}\)) by sulfate ions (SO\({}_{4}\)\({}^{2-}\)), leading to its transformation into AFit. However, it is worth noting that the chloride ions  
Figure 5: Raman spectra of Mix1 (100% CEMI) after 1 and 11 days of exposure to sulfate (EXP1) and sulfate-chloride (EXP3). bonded to C-S-H were not destabilized by Na\({}_{2}\)SO\({}_{4}\), as the quantity of this bound chloride was minimal. Furthermore, it is also worth noting that the pH drop in the concrete itself (not the surrounding solution), resulting from a sulfate attack, contributed to the destabilization of [PERSON]'s salt [22]. The peak at 1685 cm\({}^{-1}\), corresponding to gypsum, was consistently present in all of the mixes due to the presence of gypsum in the pastes. The peak at 1102 cm\({}^{-1}\) was observed in all mixes when sulfate was present (as shown in Figure 7). This indicates the formation of gypsum and ettringite, resulting from the chemical reaction between the hydrated products and sulfate ions. The peak at 619 cm\({}^{-1}\), attributed to ettringite, was present in all mixes when only exposed to sulfate. However, its formation was delayed in the presence of both sulfate and chloride. It appeared after 3 days in Mix1, 1 day in Mix2, 18 days in the Mix3, and 11 days in the Mix4. These results suggest that the presence of sulfate destabilized Friedel's salt and that the presence of chloride, along with sulfate, retarded the formation of ettringite. This implies that chloride attenuates the effect of sulfate attack while reducing the binding capacity of chloride. Comparing the four mixes in terms of chemical reactions was challenging, as they were attacked at an early age before completing the hydration process.