Ceramics-Silikáty 43, (2) 52 - 55 (1999) |
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ELECTROKINETIC POTENTIAL MEASUREMENTS IN SiO₂ - H₂O SYSTEM IN THE PRESENCE OF CALCIUM SULPHATE DIHYDRATE |
Fasurová Naděžda, Hlavica Jaromír |
Technical University of Brno,
Institute of Material Chemistry,
Purkyňova 1 18, 612 00 Brno, Czech Republic
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The nature of the hydration, or gelation processes in SiO₂-H₂O system in the presence of calcium sulphate dihydrate was studied by electrokinetic potential measurements. SiO₂ sol contained 31.47 wt.% of silicon dioxide and the concentration of the calcium sulphate dihydrate was varied between 0.2 and 10.0 wt.%. Calcium ions presumably tend to become incorporated in the surface layer and form a new type of particles composed of a nucleus SiO₂ and a surface layer C-S-H whose significance will increase with increasing amounts of Ca²⁺ ions. Increasing amount of calcium sulphate dihydrate causes the lowering of pH value and rate of gelation of individual SiO2 is higher. In these condition, calcium ions cannot form surface layer of C-S-H gel. |
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