Effect of Temperature on Thermal Properties of Ultrahigh-Performance Concrete

Data on temperature-dependent thermal properties of concrete are critical for fire-resistance evaluation of concrete structures. This paper presents the effect of temperature on thermal properties of different types of ultrahigh-performance concrete (UHPC). A set of thermal property tests were carried out on UHPC specimens in the 20°C–800°C temperature range for measuring thermal conductivity, specific heat, mass loss, and thermal expansion. The test variables included type of UHPC [with steel, polypropylene (PP), and hybrid fibers] and temperature range. Data from the tests were used to evaluate the effect of temperature on thermal conductivity, thermal expansion, specific heat, and mass loss variations in UHPC. Furthermore, the measured test data were utilized to propose relations expressing each thermal property as a function of temperature. The proposed relations can be used as input data for evaluating fire resistance of structures fabricated with UHPC. In addition, high-temperature thermal properties of UHPC were compared with those of conventional normal-strength concrete (NSC) and high-strength concrete (HSC). Data from these tests show that temperature has a significant influence on the thermal properties of UHPC, while the presence of steel or PP fiber reinforcement has very little influence on the thermal properties of UHPC. Also, the thermal conductivity and thermal expansion of UHPC is slightly higher and mass loss and specific heat are lower than that of NSC and HSC in the 20°C–800°C temperature range.