A hydraulic binder based on slag cement, the slag cement including 20 to 80 weight % relative to a total weight of slag cement, of a blast furnace slag or a mixture of blast furnace slags, relative to the total weight of the slag cement, the hydraulic binder including an acceleration additive that is a ternary system including at least one alkali metal hydroxide in an amount such that, during mixing with water of the hydraulic binder, a molar concentration of the alkali metal hydroxide in the water is from 0.05N to 0.60N, preferably from 0.20N to 0.40N; an alkali metal sulfate at a rate of from 0.2 to 3 weight % of the slag cement; and a source of calcium sulfate in such a proportion that the content of calcium sulfate (CaSO.sub.4), relative to the weight of the slag cement, is from 2 to 7%.