**3. Materials**

This study was conducted on pastes prepared from four different low-lime calcium silicate cements, referred to as #1, #2, #3 and #4 cements, respectively. The cements were characterized by an X-ray Fluorescence (XRF) technique and the results are shown in Table 1.


**Table 1.** XRF oxide composition of the cements.

Comparing the oxide compositions of the cements, it can be seen that while they contained similar quantities of CaO (in the range of 43–46%), their SiO2 content varied from 51.5% for cement #1, to 43% for cement #4. Regarding other minor oxides (Al2O3, Fe2O3, MgO, K2O), the lowest amount was found in cement #1, whereas the highest amount was found in cement #4. All cements have similar values of LOI, except cement #2, which had an LOI about twice as high as the LOI values of other cements. The lowest alkali content was found in cement #1, and the highest was present in cement #3.

Carbonated cement paste samples were prepared by hand, mixing small amounts of cement powders with de-ionized water at water-to-cement ratio of 0.35. Once mixed, the pastes were placed in a thin (1.0–1.5 mm) layer in the VWR sterile polystyrene Petri dishes with diameter of 60 mm and the height of 1.5 mm. Immediately after completion of casting, the paste-containing Petri dishes were placed in VWR Symphony 1.4A CO2 incubator, where they were carbonated for 5 days. The environmental conditions within the incubator were as follows: temperature 23 ◦C 90–100% relative humidity and 20% concentration of carbon dioxide. After the completion of carbonation, the paste samples were pulverized with mortar and pestle, and stored sealed in glass vials before being used for testing. Prior to being subjected to sulfate solution exposure, the powdered carbonated paste samples were characterized using thermal (TGA), XRD and FT-IR techniques. The results of these analyses are presented elsewhere [1].
