Nowadays, some nuclear wastes remain classified as being deprived of an appropriate treatment facility. As producer of such wastes, the CEA strongly works, among others, on the conditioning of radioactive hydraulic oils into cementitious materials. Alkali-activated materials have proven to be very efficient for the stabilization/solidification (S/S) of such wastes, leading to strong composite materials. In this study, two alkali-activated binders based on metakaolin (i.e. geopolymer) or blast furnace slags were used for the immobilization of a model oil at 20% by volume. Among others, in-situ hydrogen production is one of the issues encountered when immobilizing radioactive wastes into cementitious materials. With the aim of limiting the degassing of hydrogen, the composite materials of that study were functionalized with a specific trapping agent (MnO2/Ag2O) which has not yet been tested in alkali-activated materials. In-situ hydrogen production was generated through gamma irradiations and aluminum corrosion to characterize the efficiency of the trapping agent in both geopolymer and alkali-activated slag binders. The first results seem to indicate that the trapping agent is more efficient in geopolymers than in alkali-activated slag.