Influence of \({P_{{O_2}}}\) and \({P_{{H_2}}}_O\) in the Atmosphere on the Rate of Changes in the System CaO-SiO2

  • V. Jesenák
  • Z. Hrabĕ


The influence of both the partial pressure of water vapour and the thermodynamic pressure of oxygen in the atmosphere on the rate and mechanism of changes in the system CaO-SiO2 (C-S) was investigated. Pellets pressed from natural α-quartz ad calcite in molar ratios C/S = 2/1 and 1/1 were treated in the temperature region 1473–1573 K in different controlled atmospheres, particularly mixtures of air/H2O and H2/H2O. The unreacted portion of both C and S were determined by chemical analysis. Intermediates of the reaction were studied by X-ray phase-analysis and on sandwiches by electron microprobe and optical microscopy. In the studied range of experimental conditions the following intermediates were found : α-cristoballite,wollastonite and dicalcium silicate. No C3S rancinite,tridymite and glass phase could be detected. The observed values of the conversions of CaO (αC ) and SiO2S) as a function of annealing time were computer-fitted to semempirical kinetic equations. The kinetic constants obtained were correlated with applied PO and PH2O values and with annealing temperature. It was found tat the reactions between CaO and SiO2 are highly accelerated by both lowering the oxygen pressure and rising the water vapour content in the atmosphere. The former effect dominates at lower, the latter at higher temperatures.


Water Vapour Fuse Silica Calcium Silicate Glass Phase Control Atmosphere 
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Copyright information

© Springer Science+Business Media New York 1977

Authors and Affiliations

  • V. Jesenák
    • 1
  • Z. Hrabĕ
    • 1
  1. 1.Department of SilicatesSlovak Technical UniversityBratislava, CheckoslovakiaSlovak

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