**4. Sulfate Exposure Experiment**

### *4.1. Experimental Setup*

In the current study, three different types of sulfate solutions were used: 0.35 M of sodium sulfate, magnesium sulfate and aluminum sulfate solutions. The pH values of the original sulfate solutions (i.e., before they contacted the paste powders) were in the range of 6–7 for sodium and magnesium sulfate solutions. On the other hand, the aluminum sulfate solution was rather acidic, with a pH level between 3 and 4.

All four carbonated paste powder samples were pulverized using mortar and pestle, passed through #200 (75 μm) sieve and submerged in sulfate solutions using a solid-toliquid ratio of 1:4. The slurry samples were kept sealed in plastic centrifuge tubes with 50 mL capacity, and stored at room temperature (23 ± 5 ◦C). They were agitated periodically twice a week by hand. Due to its acidic nature, the mixing of the aluminum sulfate solution with paste powders resulted in the release of CO2 gas bubbles from the decomposition of calcium carbonates. For this reason, the tubes containing aluminum sulfate solution were sealed only after the bubbling of CO2 has ceased. In addition to the sulfate solutions, paste powder samples were also submerged in de-ionized water. Ultimately, the exposure test was held for 120 days. At different time periods (0.5, 1, 5, 10, 20, 60, 90 and 120 days) of exposure, 16 samples in total (four different paste sample slurries per each solution type) were taken from the set for further analysis.
