Gels in a CaO-SiO2 (20:80 wt%) system were prepared in a heterogeneous phase. The following phase-transfer catalysts were tested : 1 8-Crown-6, 1 5-Crown-5 and tetrabutylammonium hydrogenosulphate. The influences of the polarity of two non-classical solvents (toluene and dichloromethane) were also studied. The degrees of polymerization and of oxide contents were analysed by infrared spectroscopy and thermal analysis. Finally, the morphology and structure of the dry and fired gels were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD).