A semi-dry method for the production of lightweight glass-fibre-reinforced gypsum

A semi-dry method, requiring less capital investment and labour than the spray dewatering method, of producing a low-density glass-reinforced gypsum material having good insulation and fire-resistant properties is described. By premixing expanded perlite, chopped glass-fibre strands and water, a relatively wet mixture is first prepared. When hemihydrate gypsum plaster is added a semi-dry crumbly mix is formed. On pressing after homogenisation water is expelled from perlite and hydrates the plaster. The material has low strength, its modulus of rupture values being 2.5 MN/m2 at 830 kg/m3 density and 1.0 MN/m2 at 680 kg/m3 density. The role of the glass fibre is to reinforce the integrity of the composite panel, which can nevertheless be suitable for some indoor applications, eg ceiling tiles. The material lends itself to decorative texturing and lamination with wood or plastic.