Effect of Fiber Content on the Tensile Properties of Steel Fiber Reinforced Concrete Exposed to Fire

The protection of new structures and the necessary evaluation/intervention measurements in the case of existing structures subjected to fire damage are research topics of importance in a worldwide scale. It is known that the use of micro-synthetic fibers reduces the occurrence of explosive spalling, and that its use with steel fibers promotes beneficial effects in terms of fire resistance. However, the current standards and recommendations do not provide an adequate approach regarding the use of steel fiber reinforced concrete (SFRC) for structural applications under fire. In this context, the present work evaluates the mechanical behavior of the SFRC subjected to an actual fire simulation, as it assesses the reinforcement capacity provided by steel fibers. The heating procedure was conducted using a vertical fire simulator that induced a single-surface fire exposure following the hydrocarbon fire curve. The post-crack mechanical behavior of samples produced with fiber contents of 0.26%, 0.45%, and 0.90% in volume (i.e. 20, 35 and 70 kg / m3, respectively) were evaluated. The post-crack tensile properties were assessed by means of the Double Edge Wedge Splitting (DEWS) test and the standard three-point bending test. Results shows that the post-crack flexural tensile strength is greatly affected by fire in both service and ultimate limit states. The results are of importance for the implementation and validation of recently developed numerical models focused on assessing the bearing capacity of tunnel structures built with SFRC.