EXPERIMENTAL STUDY ON FIRE RESISTANCE OF AXIALLY RESTRAINED HSC & FRHSC COLUMNS

Fire resistance tests were conducted on HSC (High Strength Concrete) columns exposed to fire on all sides under axial and eccentric loading, HSC columns exposed to fire on three sides under axial loading and FRHSC (Fiber Reinforced High Strength Concrete) columns in 4-and 3-sided fire exposure under axial loading. All the tests used ISO-834 standard fires and all the specimens were under axial restraint. Temperature at the mid-height of the specimens, deformation, axial constraint counterforce, and fire resistance were observed. The spalling which happened in the experiment was analyzed. The results show that, for HSC columns, high load and high axial restraint stiffness ratios result in initial spalling happening early in the fire exposure stage. Bridge connection from the inclusion of PP (polypropylene) fiber in the concrete mix reduces the risk of spalling happening in the fire's initial stage, and in the later stage including PP allows water vapor to escape from the pores caused by fiber melting. Eccentric load decreases HSC columns fire resistance under otherwise identical conditions. Bending deflection toward the unfired side arises when columns were placed under axial load in 3-sided fire exposure. Additional axial force, which arises in columns with axial restraint during the expansion stage, accelerates the occurrence of first spalling in HSC columns in fire.