Constructional cement

A method of making a constructional cement which comprises (a) artificially preparing a particulate chemical combination of oxides selected from the group consisting of anorthite with excess silica in solid solution in the anorthite wherein the excess silica is present in amount of at least 5% by weight, and anorthite with albite in solid solution in the anorthite wherein the albite is present in amount not greater than 30% by weight, by sintering an intimate mixture of minerals which severally contribute the constitutent oxides of the combination or of compounds which form said oxides under sintering conditions, in stoichiometric proportions to form said combination, whereby said oxides combine, and grinding the sintered product;

• and (b) reacting said ground product with an amount sufficient to bring about hardening thereof, of an aqueous solution containing 35 to 60% by weight of orthophosphoric acid.