Abstract: A tectoaluminosilicate cement which consists of K, Ca and aluminosilicates plus, optionally, Li, Na and Mg, contains: a phyllosilicate dehydroxylated at a temperature between 500.degree. and 900.degree. C., reactive amorphous silica, reactive calcium silicate glass or reactive calcium aluminosilicate glass with a Ca:Si ratio of .gtoreq.1 and alkali silicate with the total formula: a(M.sub.2 O) * x(SiO.sub.2) * y(H.sub.2 O) in which M=Li, Na or K, a=0-4, x=0-5 and y=3-20, the overall Si:Al ratio being .gtoreq.1. The tectoaluminosilicate cement preferably alkali hydroxide. The dehydroxylated phyllosilicate is a metakaolin giving tectosilicate structures. The reactive amorphous silica is a dealuminated phyllosilicate, a fly ash dealuminated with mineral acids, where applicable, a fine-grained crystalline form of SiO.sub.