## 4 Discussion  
The pH elevation in the solutions provides strong evidence of ongoing chemical reactions. Furthermore, this phenomenon was verified by the observed visual color changes (shown in Figure 3).  
The TGA test results strongly indicated a substantial consumption of portlandite in the presence of sulfate ions. Concurrently, under identical exposure conditions, AFm was completely depleted. Also, at temperatures below 200 \({}^{\circ}\)C on the TGA curve, a significant loss of mass was observed in comparison to EXP0 and EXP1, indicating the formation of ettrinigite. The FTIR analysis corroborated these findings by revealing significant ettrinigite formation when subjected solely to sulfate exposure. Interestingly, the corresponding pH levels in this scenario were notably elevated, suggesting heightened kinetics in the chemical reactions between sulfate and cementitious materials. Turning to porosity, a more pronounced increase was observed in specimens exposed solely to sulfate after 25 days. This signifies chloride's mitigating influence on sulfate attack. This observation aligns well with the depletion of sulfate ions in the sulfate-only solution, as monitored through Raman spectroscopy, which can be an easy way to monitor the kinetics of sulfate attack.  
The FTIR analysis results revealed the presence of [PERSON]'s salt exclusively in the mixes exposed to chloride. Additionally, a concurrent reduction in portlandite content was identified, which can be linked to the outcomes of the porosity test. In EXP3, the rise in porosity, when compared to EXP2, was relatively modest, despite the presence of chloride along with sulfate, which also causes an increase in the porosity (double effect of sulfate and chloride). This could potentially indicate that, apart from the minimal formation of ettrinigite, the Friedel's salt formation (binding of chloride ions) was significantly low or possibly absent, as implied by the FTIR findings. The co-presence of sulfate with chloride could expedite the diffusion of chloride ions due to the absence of bound chloride ions.  
While no substantial differences were observed among the various mixes regarding chemical reactions, it is worth noting that the inclusion of multiple SCMs postponed ettrinigite formation. This resulted in better stability in terms of porosity changes (especially in Mix3), and improved the mixes' resistance to attacks.  
The comprehensive analysis of the chemical transformations triggered by sulfate and chloride exposure in these low-carbon cementitious powders has provided a foundational understanding of how these ions interact with cement-based materials. However, it is crucial to expand the investigation to encompass larger solid samples, allowing for a more comprehensive exploration of the physicochemical impact of sulfate and chloride within a complex matrix that mimics real-world conditions. A critical area that requires focused attention is the transfer properties governing the diffusion and migration of sulfate and chloride ions within the cement matrix. These transfer properties play a pivotal role in determining the extent of ion penetration, their interaction with hydration products, and the resulting chemical alterations influencing the material properties themselves.  
In order to better understand the chemical changes that occurred, a schematic representation is shown in Figure 10.