Microstructure of glass fibre reinforced water resistant gypsum binder composites

Abstract

The microstructure at the interface was studied in case of glass fibre reinforced gypsum binder composites exposed to water, accelerated ageing, i.e. alternate wetting and drying cycles at 27° to 60°C and to natural weathering. After 50 wetting and drying cycles at 60°C, deposition of gypsum binder products was observed in an irregular manner at the surface and in between glass fibre strands. Durability of E-type glass (borosilicate glass) fibres used as reinforcement in the water resistant gypsum binder composites has been assessed after exposure to aqueous extract of gypsum binder at temperature 27° to 60°C. The extracted glass fibres were characterized by scanning electron microscope and weight loss. Up to 40°C, no damage to glass fibres was noticed but at 50°C and 60°C, the glass fibres are attacked and erosion of glass surface takes place leading to the weakening of the interfacial bond at the matrix and fibre interface. A correlation between the durability of glass fibre and its weight loss was established. The loss in durability of glass fibre governs the flexural strength of gypsum binder composites tested under accelerated ageing.