## 3 Results
### Methodology for Estimating Alkali Ions in the Concrete Pore Solution
[17] have proposed a thermodynamic model to study the effects of composition and temperature on the pore solution. They found that with longer ages of hydration, the ion concentrations in the pore solutions are similar at all temperatures, in general. However, the concentrations of sulfate and aluminum increased at high temperature. This fact leads to the promotion of ettrinigite solubility, which results in a decrease of the hydroxide ions in the pore solution. Nevertheless, the Portland cement pore solution was oversaturated with regard to ettrinigite, probably due to the low Al/Ca and Al/sulfate ratio, which undermines the precipitation process of ettrinigite [17]. Table 3 shows the water-soluble alkalis, as determined by the method described in Section 2.3. According to [PERSON] [8], it is assumed that all of the water-soluble alkalis in cement are alkali cations that are present as sulfates (Table 3). [PERSON] proposed an assumed amount of 35% of the total weight of Na\({}_{2}\)O in the cement, present as a sulfate, and an amount of 70% of the total weight of K\({}_{2}\)O in the cement, present as sulfate, when the proportions are unknown. However, in this paper, an average of 53% of the total weight of Na\({}_{2}\)O was Na\({}_{2}\)O present as a sulfate in the cement, whereas 97% of the total weight of K\({}_{2}\)O was K\({}_{2}\)O present as a sulfate in the cement (Table 4). The high variability with regard to the proportion of the soluble alkali cations against the total alkali cations suggests that it will be necessary, in the new proposed method, to use experimentally determined results. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Code** & **Cement** & **Na\({}_{2}\)O\({}_{4}\)** & **Na\({}_{2}\)O\({}_{4}\)** & **K\({}_{2}\)O\({}_{4}\)** & **Na\({}_{2}\)O\({}_{4}\)** & **Na\({}_{2}\)O\({}_{4}\)** & **Na\({}_{2}\)O\({}_{4}\)** \\ \hline
1 & CEM 1 52.5 R & 0.23 & 0.83 & 0.13 & 0.81 & 58 & 98 \\
2 & CEM 1 52.5 R (white) & 0.05 & 0.56 & 0.02 & 0.53 & 41 & 95 \\
3 & CEM 1 42.5 R (8.73 & 0.53 & 0.60 & 0.31 & 0.56 & 58 & 93 \\
4 & CEM 1 52.5 R-SR 5 & 0.49 & 0.57 & 0.30 & 0.56 & 61 & 98 \\
5 & CEM 1 42.5 R & 0.33 & 0.88 & 0.20 & 0.87 & 61 & 99 \\
6 & CEM 1 52.5 R (low-alkali) & 0.14 & 0.52 & 0.06 & 0.51 & 40 & 99 \\ \hline \hline \end{tabular} Average percentage & - & - & - & - & 53 & 97 \\ [PERSON]’s average proposal (\%) [8] & - & - & - & - & 35 & 70 \\ Minimum percentage & - & - & - & - & 40 & 93 \\ Maximum percentage & - & - & - & - & 61 & 99 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Fractional distributions of the water-soluble alkalis (sulfate alkalis) in the total alkali content. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Code** & **Cement** & **Na\({}_{2}\)O\({}_{4}\)** & **K\({}_{2}\)O\({}_{4}\)** \\ \hline
1 & CEM 1 52.5 R & 0.13 & 0.81 \\
2 & CEM 1 52.5 R (white) & 0.02 & 0.53 \\
3 & CEM 1 42.5 R-SR 3 & 0.31 & 0.56 \\
4 & CEM 1 52.5 R-SR 5 & 0.30 & 0.56 \\
5 & CEM 1 42.5 R & 0.20 & 0.87 \\
6 & CEM 1 52.5 R (low-alkali) & 0.06 & 0.51 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Water-soluble alkalis determined in the cement, which are considered as cations present in sulfate form (%). Another source of error can be found in the testing method, because it is assumed that all the water-soluble alkali in the cement, mainly sulfates, will be dissolved. However, it could be possible that not all of the water-soluble alkalis in the cement were dissolved [18]. Then, the real amount of alkalis present as sulfates could be even higher. According to [PERSON] [8], most of the potassium normally is present as potassium sulfate whereas sodium was not the case. Table 4 shows that sodium is bounded in cement paste hydrates in a higher extension than potassium, in agreement with other authors [16; 19]. Whereas [PERSON] proposed that only about 70% of the potassium is water-soluble, in this research, almost all of the potassium is water-soluble. Also, he proposed a procedure for determining the alkali binding capacities of hydrated Portland cement paste.