Hydraulic binder for mortar composition

A hydraulic binder for a mortar composition comprising, by weight, from 10 to 70% of at least one ladle slag, from 0 to 35% of Portland cement, from 5 to 45% of calcium sulfate and from 2 to 35% of aluminous cement, the at least one ladle slag having a particle size distribution by volume such that the D50 is less than 40 μm,

• wherein the ladle slag has a chemical composition which comprises the following constituents within the limits hereunder expressed as percentages by weight:
• SiO2:
• 2-20%,
• CaO:
• 30-60%
• Al2O3:
• 20-50%, and
• wherein the ladle slag comprises at least one crystalline phase of calcium aluminate type in a content by weight of between 10 and 60%.