Synthesis of Calcium Silicate Hydrate with Ca/Si = 2 by Mechanochemical Treatment

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An amorphous, C‐S‐H‐like phase with Ca/Si = 2 was synthesized from amorphous precipitated silica, calcium oxide, and water by mechanochemical treatment using a vibration mill at room temperature. The product was studied by XRD, 29 Si MASNMR, TEM, analytical TEM, and TGA‐DTA. After 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 resembles the C‐S‐H formed hydrothermally or by cement hydration except it has no reflection at 0.182 nm. The 29 Si NMR results revealed a silicate anion structure of C‐S‐H‐like phase consisting mainly of a mixture of a monomer and a dimer. On heating, the C‐S‐H‐like phase decomposed into β‐dicalcium silicate below 1000°C.