Materials produced by foaming of particular cementitious compositions of geopolymeric or pozzolanic type in highly alkaline milieu without appreciable addition of dissolved silicate. Methods of manufacturing cementitious compositions are provided by using hypochlorite as a foaming agent therein. An aqueous cementitious slurry may be activated, first to foam, and then to set hard, by a process of applied heat, into useful materials and articles of hardened cellular cementitious composition. This process suggests advantage for a production process.