Abstract
A calcium silicate hydrate, Ca1.5 SiO3.5·xH2O, was synthesized either by a hydrothermal or mechanochemical method using rice husk ash (RHA) and calcium hydroxide as raw materials. The particle diameters of the products prepared by the hydrothermal synthesis were mostly less than 10 μm with an average between 4.8 μm and 7.9 μm and were varied according to the synthetic method and conditions. Finer calcium silicate hydrate could be prepared by the mechanochemical synthesis. Similar to C-S-H gel in Portland cement paste the product appeared to be flocs with a porous structure and large specific surface area. When the product was heated it gradually lost the water that existed in its structure and pores but kept amorphous state up to 750°C. Above 780°C it was changed to wollastonite.
