Fire resistance of ultra-high performance concrete columns subjected to axial and eccentric loading

This paper experimentally investigated fire resistance of UHPC and HPC columns under the ISO 834 fire curve. Effects of concrete strength, inclusion of fibers, and load eccentricity were investigated. Spalling behavior, failure mode, temperature distribution, axial deformation, mid-height column deflection, and fire resistance were measured and analyzed. From the results, columns with plain UHPC matrix were highly susceptible to explosive spalling due to its dense microstructure and low permeability, which led to premature failure and low fire resistance. Although the addition of 3 kg/m³ of PP fibers was higher than the dosage recommended in Eurocode 2, it did not eliminate spalling for the axially-loaded UHPC columns. With the addition of hybrid PP and steel fibers, the UHPC columns only showed marginal spalling under axial loading, which significantly improved the fire resistance. However, load eccentricity promotes explosive spalling of UHPC columns especially on the compression side of bending, which reduced the fire resistance.