Use of Sodium Metasilicate as Silica Source and Stabilizing Agent in Two–Part Metakaolin–H2o2 Geopolymer Foams

•Sodium metasilicate was used as a complementary silica source in two-part geopolymer foams.•Sodium metasilicate acted as a stabilizing agent in H2O2–geopolymer foam.•H2O2 should be limited to a SiO2/Al2O3 ratio up to 2.5 for curing at 50 °C.•SiO2/Al2O3 = 2.5 and H2O2 = 6.0% were most conducive to the porous structure.•Produced geopolymer foams can be used as lightweight insulating cores.