Melt extract fibre reinforced composites
This research has examined the two largest potential markets for melt extract stainless steel fibres, namely sprayed concrete and refractory concrete. An emphasis was placed on developing appropriate test methods that would produce experimental data of a practical and useful nature. A comparison was made at various stages between melt extract fibres and more conventional drawn wire fibres. The spraye~ concrete programme studied three fibre dispersion techniques on site and produced test panels between 50mm and 150mm thick from which beam and core specimens were cut. Information was obtained on fibre rebound and the effects of specimen age, fibre type and content on compressive, flexural and splitting strengths and toughness. Rebound of drawn wire fibres was found to be twice that of melt extract fibres on plywood panels and approaching two and a half times greater on rock. The addition of steel fibres produced increases in compressive and flexural strengths, typical values for a 7.5% dry mix content being 15% and 55% respectively. Two splitting tests on cores (Brazilian and point-load types) were investigated as possible methods of on site quality control and results indicated linear relationships between flexural and splitting strengths. The post-crack toughness was examined in terms of the area under the beam load/deflection curve and a computer programme was used to evaluate a variety of toughness indices. Deflection cut-off crieria based on the ultimate load co-ordinates or fixed values of deflection were found preferable to those calculated from the first crack deflection and the use of the elastic area under the fibrous beam's curve as the denominator of the index proved less reliable than using that of the unreinforced material. The inclusion of 7% by weight of melt fibres increased the toughness by over 30 times when using the 2.3mm fixed deflection criteria. [... continued].