Residual mechanical characteristics and spalling resistance of fiber reinforced self-compacting concretes exposed to elevated temperatures

The study presented in this paper concerns the effect that polypropylene fibres have on the properties of SCC of different strength classes when exposed to elevated temperatures. A total of six different SCC and two normal concrete mixtures were produced. The strength classes of the mixtures were C25/30 and C30/37.The specimens produced were placed at the age of 120 days in an electrical furnace and the heat was applied with a rate of 5 °C/min. The tested temperatures were 300 °C and 600 °C. Once reached, the maximum temperature was maintained for 1 h. Then the specimens were naturally cooled down to ambient temperature in the furnace. The properties measured after heat exposures were the compressive strength, splitting tensile strength, water capillary absorption and ultrasonic pulse velocity.It was noticed that, the spalling tendency was increased for specimens of higher strength class C30/37 irrespective of the mixture type (SCC or NVC). Such an explosive behavior was not observed when polypropylene fibers were added in the mixtures; however, in this case the residual mechanical characteristics of concretes were significantly reduced.

► We examined the performance at elevated temperatures of two normally vibrated concretes and six self compacted concretes.
► The strength classes of the mixtures were C25/30 and C30/37.
► Polypropylene fibres with a length of 6 and 12 mm were used to produce fibre reinforced SCC.
► The spalling tendency was increased for specimens of higher strength class irrespective of the mixture type (SCC or NVC).
► Both 6 m and 12 mm fibres had the same positive effect since all fiber reinforced SCC mixtures did not perform any spalling.