Evolution of the Fibre-Matrix Interactions in Basalt-Fibre-Reinforced Geopolymer-Matrix Composites after Heating

Abstract

The evolution of fibre-matrix interactions in basalt fibre reinforced geopolymer matrix composites after heating to 600, 800 and 1000°C was investigated by means of SEM, EDS and XRD analyses. The basalt fibres showed no significant interfacial interaction up to 600°C. The appearance of the fracture surfaces also remained largely unchanged. At higher temperatures, crystallisation reactions within the fibres and the Na-geopolymer matrix, respectively, could be observed along with an increasing embrittlement of the composite. Softening of the fibres and the development of several distinct reaction zones within the fibres was clearly evident after heating to 800°C and 1000°C. The formation of an iron-rich outer reaction zone within the fibre was observed above 800°C. The interaction between fibre and matrix resulted in the formation of a crystalline albite phase after heating to 1000°C. It is suggested that basalt fibres have great potential as reinforcements for the development of cost-efficient geopolymer matrix composites and may be used for applications up to 600°C.