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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.2 contained in calcinated clays, a silicic acid gel, thermally activated by alkali-activated aluminosilicate, obtained by sintering an aluminosilicate with alkali carbonate at a temperture between 800.degree. and 1,200.degree. C., the alkali and aluminosilicate components being mixed in the ratio 1:6 to 1:1, and/or microsilica ('silica fume'). The alkali metal activator may be prepared in situ from the dealuminated phyllosilicate and/or from the silicic acid gel in the presence of the alkali hydroxide. A bonding matrix obtained from the tectoaluminosilicate cement by reacting with water in the ratio 3:1 to 6:1 consists essentially of the formula: (Li, Na).sub.0-7 K.sub.1-6 Mg.sub.1-0 Ca.sub.3-0 [Al.sub.4 Si.sub.6-14 O.sub.21-36 ].(0-15H.sub.2 O).

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First Claim