METHOD FOR THE MANUFACTURING OF CEMENTITIOUS C-S-H SEEDS

The invention describes a process for the manufacturing of C-S-H seeds comprising the steps of: mixing one or more industrial wastes and by-products comprising Ca and Si with at least one doping agent comprising one or more doping elements selected from the group of P, B, S and their mixtures, in such a proportion that the molar ratio Ca : (Si + doping element) in the mixture ranges between 0.5 and 2.5; combining the mixture with water so that the solid-water ratio by weight in the resulting mixture is equal to or larger than 0.2, and submitting the resulting mixture to hydrothermal treatment. The invention describes the so obtained new C-S-H seeds, additive compositions, comprising them, and its use as hardening accelerator and seeding additive for concrete or other cement based materials