Performance of fibre reinforced refractory concrete

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Steel fibres are commonly used in the refractory industry to reinforce high temperature concretes, though limited information is available on the mechanical properties of steel fibre refractories. this research has examined the influence of fibre geometry, fibre alloy composition and fibre content of stainless steel melt extract fibres on the performance of a proprietary 1400°c medium duty calcium aluminate bonded castable. it has also examined whether it is necessary to obtain flexural and toughness measurements at temperature in order to properly evaluate the performance of fibre reinforement or whether it is possible to obtain meaningful results from a much simpler room temperature test. the construction of a simple insulating box allowed flexural tests to be carried out at temperature in a standard testing machine, after the specimen having been cyclically heated and cooled in a purpose-built spalling resistance furnace. whilst testing hot is a better model of service conditions, testing at room temperature after cyclic conditioning is clearly easier. the research has shown that cold testing overestimates flexural strength and underestimates toughness, though the relationships with aspect ratio are similar, flexural strength and toughness increasing with aspect ratio at both test temperatures. for flexural strengthening, an aspect ratio of around 60 would appear to be a sensible choice. however, if improvements in toughness are taken to be a better indicator of refractory spalling resistance, the results suggest that a fibre aspect ratio of around 80 is more appropriate. above these aspect ratios the improvements in performance are small and the likelihood of problems in mixing and placing increases.