Patent ID: 8628612

Claim:
A process for preparing, starting from a slag material, a filler for use in construction materials which contain a hydraulic or bituminous binding agent, characterised in that use is made of a slag material containing γ-dicalcium silicate; and in that the process comprises the steps of: removing a finer fraction from the slag material to divide the slag material in said finer fraction and in a coarser fraction, wherein the coarser fraction comprises crystalline phases and has a γ-dicalcium silicate content which is less than 4% by weight of said crystalline phases, wherein the coarser fraction comprises particles having a particle size greater than 0.75 mm, and wherein the finer fraction comprises particles having a particle size that is smaller than the particle size of the particles of the coarser fraction; and finely milling at least a portion of said coarser fraction of the slag material to obtain a filler, from only the coarser fraction, of which at least 50% by weight is formed by particles not bigger than 63 μm.