Experimental investigation of triaxial strength of ultra-high performance concrete after exposure to elevated temperature

Equipped with excellent strength and energy absorption capacity, ultra-high performance concrete (UHPC) is a promising material to improve structural resistance against extreme loads. Material and structural tests at ambient temperature have been conducted extensively on UHPC specimens in recent years, and its mechanical properties have been well-documented. In this study, a hybrid steel and polypropylene (PP) fibre reinforced UHPC is investigated under uniaxial and triaxial compression states after exposure to elevated temperatures. Cubic (50 mm) and cylindrical specimens (50 mm diameter x 100 mm height) were first heated in electric furnace to target temperatures, i.e. 200 degrees C, 400 degrees C, 600 degrees C, 800 degrees C and 1000 degrees C. After naturally cooled down to ambient temperature, the specimens were tested under uniaxial compression and triaxial compression with confining pressure ranging from 5 to 40 MPa. The triaxial stress-strain relationships and failure modes after exposure to elevated temperatures were then compared and discussed. Several common failure criteria for concrete material were adopted to describe the high temperature effect on UHPC's strength. An empirical model for reproducing the triaxial compression stress-strain curves of UHPC after elevated temperature was proposed. (c) 2021 Elsevier Ltd. All rights reserved.