Patent ID: 6936098

Claim:
A process for producing blended cement, wherein the cement contains Portland Cement that has been mixed thoroughly with a microfiller and optionally a water reducing agent to a dry cement mixture, and that also includes a fine supplementary cementitious material selected from the group consisting of blast furnace slag, fly ash, quartz, silica, amorphous silicon dioxide, limestone, recycled concrete, and mixtures thereof, said process comprising the steps of: subjecting the supplementary material to a first grinding step while in a dry state to provide a Blaine specific surface of at least 1000 cm 2 /g, grinding the ground supplementary material in a second grinding step together with at least 20% by weight of a total grinding mass of a highly reactive cement mixture in a dry state to achieve a blended cement having a Blaine specific surface of at least 3000 cm 2 /g, wherein the highly reactive cement mixture contains cement particles and at least one of the components selected from the group consisting of an SiO 2 -containing microfiller and a polymer in the form of a powdery water-reducing agent, and wherein the highly reactive cement mixture is first treated in a grinder with vibrating grinding media in which the cement particles are subjected to impact impulses giving the cement particles an increase in surface energy and chemical reactivity.