Method for oxidizing treatment of steel works slag and resulting LD slag

A process for the treatment of a steel slag so as to obtain a treated slag comprising a hydraulic binding material, the process consisting essentially of:

• forming a mixed and oxidized liquid steel slag by injecting oxygen or a mixture of gases containing oxygen into a liquid steel slag at a temperature of 1350 to 1550° C., the injection of oxygen or of a mixture of gases containing oxygen being regulated to obtain a pressure of oxygen or a mixture of gases containing oxygen in equilibrium with the liquid steel slag of 102 to 5.105 PA;
• adding to and dissolving in the mixed and oxidized liquid slag a source of alumina and a source of lime and optionally a source of silica and/or iron;
• and
• cooling the slag until the slag solidifies;
• wherein the quantities of alumina and lime are such that, in the treated steel slag, the proportions of alumina is greater than 25% by weight and the proportion of lime is equal or greater than 40% by weight, the quantities of alumina and lime and optionally of silica and/or iron added, and the rate of cooling are such that the treated slag obtained has a mineralogical composition with one of the following characteristics:
• (a) an amorphous vitreous phase;
• (b) a first set of phases comprising 10–40% by weight CA, 20–50% by weight C2AS, 30–50% by weight C6AF2, and 10–30% by weight C2S;
• (c) a second set of phases comprising 20–40% by weight C2F, 10–30% by weight C2AS, 20–50% by weight C6AF2 and 10–40% by weight C2S;
• and
• (d) a mixture of an amorphous vitreous phase and of the first or second set of phases.