Xonotlite Heat-insulating Material with Bulk Density of 0.1

The mixture of silica powder, a by-product of metalic silicon, and milk of lime, prepared from quick lime of fine grain, was stirred in an autoclave and treated hydrothermally under the following conditions; molar ratio of CaO/SiO2 0.975, weight ratio of water/total-solid 24, pressure 12kg/cm2, temperature 191°C, reaction time 8h. Thus milky slurry consisting of xonotlite was prepared.Xonotlite aggregate grain prepared by this method was fairly different from that by the previous method in which silica sand was used as raw material. As it is shown in the figures, the grain is hollow and has finer size, and xonotlite single crystals constituting the aggregate grain are relatively longer and thinner.The molded material from this slurry is more excellent than the previous one; bulk density is 0.1, bending strength is 6kg/cm2 and shrinkage at 1000°C is about 1%. Bending strength of a material having bulk density of 0.2 becomes over 20kg/cm2.