Glass fibre reinforced cement and gypsum products

Abstract

Glass fibre reinforced cements and gypsum plaster provide examples of composite materials where both the components are brittle and the matrix phase fails at a much lower strain than the fibre. Porosities of the order of 30% or more are usually present in these matrices. The interfacial bond that develops between the fibre and the matrix is very discontinuous and irregular. The dispersion of glass fibre in the matrix is not easy. When chopped multifilament strands are distributed in the matrix by a spraying process, the tensile and flexural strength of the composite material produced from gypsum plaster reach maximum values around 10% by volume of fibre addition. Beyond the elastic limit, the composite material exhibits a quasi-plastic behaviour until it fails by fibre pull-out. Fire resistance and impact strength of plaster are greatly improved by fibre incorporation. Glass fibres now available commercially are not durable in the alkaline medium present in hydrating Portland cements. Experimental fibres produced from more alkali-resistant glasses are being studied for their suitability in reinforcing cements and concrete. It can be foreseen that given a durable glass, the composite material will have pronounced advantages over existing sheet materials in respect of impact strength and resistance to cracking, tensile and bending strength and fire resistance.