SYNTHESIS OF CALCIUM SILICATE HYDRATE WITH CA SI=2 BY MECHANOCHEMICALTREATMENT/

An amorphous, C-S-H-like phase with Ca/Si = 2 was synthesized from amo rphous precipitated silica, calcium oxide, and water by mechanochemica l treatment using a vibration mill at room temperature. The product wa s studied by XRD, Si-29 MASNMR, TEM, analytical TEM, and TGA-DTA. Afte r 14 h of treatment, the starting materials react to form an amorphous phase (C-S-H-like phase). The XRD pattern of C-S-H-like phase resembl es the C-S-EI formed hydrothermally or by cement hydration except it h as no reflection at 0.182 nm. The Si-29 NMR results revealed a silicat e anion structure of C-S-H-like phase consisting mainly of a mixture o f a monomer and a dimer. On heating, the C-S-H-like phase decomposed i nto beta-dicalcium silicate below 1000 degrees C.