Kazuhiko Kubo

Studies on Calcium Silicate Hydrate for Industrial Use (III)

The mixture of silica powder and milk of lime was stirred in an autoclave and treated hydrothermally under the following conditions; molar ratio of CaO/SiO2 0.80, weight ratio of water/total-solid 12, pressure 8kg/cm2, temperature 175°C, for 4-8hrs. Thus milky slurry consisting of tobermorite was prepared.The slurry contains 8% of total solid matter and its viscosity is 1.5-2.0 poise. Crystals are tobermorite whose (002) spacings are 11.2-11.3A. Grains are spherical aggregates with 5-70μm diameter having inter-twining structures of plate-like tobermorite crystals as shown in Fig. 5, 6 and Fig. 8.The slurry is easily dehydrated and shaped in a mold under pressure and the molded material can be hardened only by drying. The properties of thus obtained light molded material are following as shown in Table 1; density 0.2, bending strength 3-4kg/cm2, thermal durability 900°C, shrinkage at 1000°C 2-3%.