Effects of pH on precipitation of quasi-crystalline calcium silicate hydrate in aqueous solution
| Autor: | J. F. Young, H. Matsuyama |
|---|---|
| Rok vydání: | 2000 |
| Předmět: |
Aqueous solution
Precipitation (chemistry) Analytical chemistry Building and Construction Nuclear magnetic resonance spectroscopy law.invention chemistry.chemical_compound Crystallinity Portland cement chemistry law X-ray crystallography General Materials Science Chemical stability Calcium silicate hydrate Nuclear chemistry |
| Zdroj: | Advances in Cement Research. 12:29-33 |
| ISSN: | 1751-7605 0951-7197 |
| Popis: | C-S-H samples were precipitated from aqueous solution containing Ca(NO3)2 and Na2SiO3 with an initial Ca/Si molar ratio of 1·3, when the pH value in the solution was varied by adding HNO3 or NaOH. A pH > 10·9 was required to obtain quasi-crystalline C-S-H, and the CaO/SiO2 ratio of the precipitate was increased with increasing pH, reaching a maximum close to the initial ratio at pH > 13. C-S-H was also precipitated with varying initial Ca/Si molar ratios at pH > 13. It was shown that the CaO/SiO2 ratios can be controlled by either varying the pH value at given initial Ca/Si ratios, or by varying the initial Ca/Si ratios at pH > 13. The C-S-H samples were investigated using X-ray diffraction and 29Si nuclear magnetic resonance spectroscopy, which identifies the connectivity of silica tetrahedra (Qx). The interlayer spacing decreased linearly, and Q1/(Q1 + Q2 + Q3) ratios increased with increasing CaO/SiO2 ratios. A good correlation between Q1/(Q1 + Q2 + Q3) ratios and interlayer spacing was observed. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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