The paper brings information concerning the synthesis and reactivity of a highly reactive dicalcium silicate using calcium silicate
hydrates as precursors. The calcium silicate hydrates were prepared by hydrothermal treatments of mixtures consisting in CaO,
amorphous SiO2 (ROMSIL) and water, under various hydrothermal conditions. C2S was obtained by thermal treatment ± at low
temperatures (700±800°C) ± of these silicates hydrates. Due to this way of processing (hydrothermal synthesis and low temperature
treatment), the dicalcium silicate obtained is very reactive and develops good compressive strengths in pressed mortar specimens
even after one day of hardening