Compressive strength and failure behaviour of fibre reinforced concrete at elevated temperatures

This paper presents the effects of elevated temperatures of 400°C and 800°C on the residualcompressive strength and failure behaviour of fibre reinforced concretes and comparison is made with thatof unreinforced control concrete. Two types of short fibres are used in this study e.g., steel and basalt fibres.The results show that the residual compressive strength capacity of steel fibre reinforced concrete is higherthan unreinforced concrete at both elevated temperatures. The basalt fibre reinforced concrete, on the otherhand, showed lower strength retention capacity than the control unreinforced concrete. However, the use ofhybrid steel-basalt fibre reinforcement recovered the deficiency of basalt fibre reinforced concrete, but stillslightly lower than the control and steel fibres reinforced concretes. The use of fibres reduces the spallingand explosive failure of steel, basalt and hybrid steel-basalt fibres reinforced concretes oppose to spalling indeeper regions of ordinary control concrete after exposure to above elevated temperatures. Microscopicobservation of steel and basalt fibres surfaces after exposure to above elevated temperatures shows peelingof thin layer from steel surface at 800°C, whereas in the case of basalt fibre formation of Plagioclase mineralcrystals on the surface are observed at elevated temperatures