Expanded material is prepared by (a) mixing milled natural silicates, silica containing clays, and stone materials, witha blowing agent; and (b) vitrifying the

摘要

Expanded material is prepared by (a) mixing milled natural silicates, silica containing clays, and stone materials, witha blowing agent; and (b) vitrifying the mixture by heating to 800-1200 deg.C, to form an expanded mass which can be cooled without recrystallisation. The silica material may be sandstone; quartz sand, pumice stone, or similar material. The whole mixture is pref. milled to a Blaine number of at least 2500. The blowing agent is pref. prepared by drying a suspension of carbon black in water glass, and then milling the dry material.