Ceramics-Silikáty 43 (2) 52-55 (1999)

ELECTROKINETIC POTENTIAL MEASUREMENTS IN SiO₂ - H₂O SYSTEM IN THE PRESENCE OF CALCIUM SULPHATE DIHYDRATE

N. Fasurová, J. Havlica 

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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