C–(N)–S–H and N–A–S–H gels: Compositions and solubility data at 25°C and 50°C

<jats:title>Abstract</jats:title> <jats:p> Calcium silicate hydrates containing sodium [C–(N)–S–H], and sodium aluminosilicate hydrates [N–A–S–H] are the dominant reaction products that are formed following reaction between a solid aluminosilicate precursor (eg, slags, fly ash, metakaolin) and an alkaline activation agent (eg Na <jats:styled-content style="fixed-case">OH</jats:styled-content> ) in the presence of water. To gain insights into the thermochemical properties of such compounds, C–(N)–S–H and N–A–S–H gels were synthesized with compositions: 0.8≤Ca/Si≤1.2 for the former, and 0.25≤Al/Si≤0.50 (atomic units) for the latter. The gels were characterized using thermogravimetric analysis ( <jats:styled-content style="fixed-case">TGA</jats:styled-content> ), scanning electron microscopy with energy‐dispersive X‐ray microanalysis ( <jats:styled-content style="fixed-case">SEM</jats:styled-content> ‐ <jats:styled-content style="fixed-case">EDS</jats:styled-content> ), and X‐ray diffraction ( <jats:styled-content style="fixed-case">XRD</jats:styled-content> ). The solubility products ( <jats:styled-content style="fixed-case"> K <jats:sub>S</jats:sub> </jats:styled-content> <jats:sub>0</jats:sub> ) of the gels were established at 25°C and 50°C. Self‐consistent solubility data of this nature are key inputs required for calculation of mass and volume balances in alkali‐activated binders ( <jats:styled-content style="fixed-case">AAB</jats:styled-content> s), and to determine the impacts of the precursor chemistry on the hydrated phase distributions; in which, C–(N)–S–H and N–A–S–H compounds dominate the hydrated phase assemblages. </jats:p>