## 3 Results
### Relationship between the Water-Soluble Alkalis and the Major Clinker Phases  
Figure 3 shows the relationship between the water-soluble alkalis obtained, following the procedure detailed in Section 2.3 (an extraction time of less than 30 min) and the C\({}_{3}\)S. It is clear that sodium uptake was preferred. Also, it was found that the concentrations of both Na\({}^{+}\) and K\({}^{+}\) in the solution apparently decreased with increasing C\({}_{3}\)S content in the clinker, particularly for K\({}^{+}\). Therefore, the less alkali ions that are available for the pore solution, because more alkali ions are bound in the C-S-H gel. Also, C\({}_{3}\)S hydration consumes less water than C\({}_{2}\)S hydration, leaving more water available for the pore solution, resulting in a dilution of the alkali ions [18]. [PERSON] et al. [26] found that the fraction of potassium uptake by low-pH cements is more than three times higher than that of sodium, disagreeing with the results shown in Figure 3. This significant difference was explained by the smaller solvated ionic radius of potassium, and because potassium ions can enter the C-S-H gel interlayer to compensate for the negative charges [26]. They also suggested that C-(A)-S-H is the phase that is mainly involved in the alkali retention by an effect of charge compensation. In addition, they reported a clear correlation between the dissolved alkali and alkali retention by C-S-H gel. In contrast, [PERSON] et al. [27] did not find any difference between sodium  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**[SO\({}_{4}^{2-}\)] Calculated** & **[OH\({}^{-}\)] Calculated** & **Na\({}_{2}\)O\({}_{\text{e}}\)** & **[OH\({}^{-}\)] Calculated** & **[OH\({}^{-}\)] Difference between** & \\
**Calculated** & **from Charge** & **(mmol/L)** & **(mole)** & **from Helmuth** & **Charge Balance and** & **(\%)** \\
**(mmol/L)** & **Balance** & **(mmol/L)** & **Equation** & **(mmol/L)** & **Helmuth Equation** (mmol/L)** \\ \hline
0.0051 & 0.2822 & 0.0091 & 0.2262 & 0.0561 & 19.87 \\
0.0016 & 0.1997 & 0.0045 & 0.2231 & \(-\)0.0633 & \(-\)39.66 \\
0.0061 & 0.3075 & 0.0117 & 0.2280 & 0.0796 & 25.88 \\
0.0055 & 0.2930 & 0.0111 & 0.2275 & 0.0654 & 22.34 \\
0.0059 & 0.3245 & 0.0109 & 0.2274 & 0.0971 & 29.93 and potassium uptake. They observed that the alkali uptake depends on the Ca/Si ratio in C-S-H and C-A-S-H gels. Thus, the lower the Ca/Si ratio is, the greater the uptake of alkali metal ions. Different behaviors of C-S-H gel concerning the binding of Na+ and K+ are observed in Figure 3, where the effects of the alkali types in cement on the alkalinity of the pore solution is observed. The C-S-H gel binds less K+ than Na+, particularly at high concentrations, and more alkali ions remain in the solution [16]. Figure 4 shows the soluble alkali concentrations in the pore solution of hydrated Portland cement paste as a function of the amount of C3S, C2S, C3S + C2S, and CaO/SiO2 ratio in the clinkers. Figure 4: _Cont._  
Figure 3: Soluble alkalis versus C3S percentage. According to various national regulations and standards, the total alkali content in cement is regulated as Na\({}_{2}\)O\({}_{\text{equivalent}}\). Therefore, the alkali types are not distinguished, and little attention is paid to the different types of alkalis, though the resultant alkalinity of the pore solution is quite different. Thus, the influence of mineral composition on the alkali concentrations was investigated using updated methods in this study. A water-cement ratio of 0.5 was considered. The C\({}_{3}\)S content in the linker ranged from 57.18% to 77.93%, while the C\({}_{2}\)S content ranged from 4.81% to 17.92%, accordingly. These totaled 76% of the clinker content. The C\({}_{3}\)A and C\({}_{4}\)AF contents in the clinker ranged from 2.42% to 11%, and from 0.67% to 13.10%, respectively. Figure 5 shows the relationship between the water-soluble alkalis of anhydrous cement and the water-soluble alkalis of hydrated cement paste after 28 days.