An Explorative Study into the Influence of Different Fibers on the Spalling Resistance and Mechanical Properties of Self-Compacting Concrete after Exposure to Elevated Temperatures

This study aims to explore the impact of different fibers on the explosive spalling resistance, residual compressive strength, residual flexural tensile strength, and mass loss of self-compacting concrete (SCC) after heating to elevated temperatures. The fiber types, fiber contents, and target temperatures are selected as the tested variables. Steel fibers (SF), polypropylene fibers (PF), and their combination are used to improve the fire resistance of SCC. Then, the specimens are tested after exposure to different target temperatures varying from 200 °C to 1000 °C and cooling down to room temperature naturally. The obtained results reveal that PF can effectively prevent explosive spalling in the SCC. Moreover, it was found that the temperature of 400 °C is a critical temperature for the residual compressive strength of fiber-reinforced SCC. Regarding the flexural tensile strength, the temperature of 200 °C was found to be a changing point of the SCC after heating to elevated temperatures. A sharp decrease in the compressive strength is observed when the target temperature exceeds 400 °C. For temperatures below 400 °C, the compressive strength is enhanced slightly with the increase of the target temperature. Moreover, incorporating a fiber cocktail is an effective way to improve the explosive spalling resistance and residual mechanical properties in the case of fire. Finally, the regression analysis was performed and the proposed correlations between the residual strengths and elevated temperatures are compared with equations in the literature. Good accuracy of the proposed correlation is achieved for fiber-reinforced SCC.