Abstract: The invention relates to a process for stabilizing an aqueous gel-forming system comprising one or more water-soluble acrylic monomer as gellifying agent, methylenebis-acrylamide co-monomer and/or one or more mono- or bivalent aldehyde as cross-linking agent, a redox catalyst system containing an alkali metal and/or ammonium persulfate as oxidizing component along with one or more amine compound as reducing component, furthermore optionally one or more water-soluble polymer for adjusting the viscosity of the solution and/or modifying the gel structure. According to the invention said gel-forming system is stabilized by saturating it with molecular oxygen.The invention relates further to a process for improving the strength and impermeability of particulate materials and/or solid articles.