Dynamic Splitting Tensile Behavior of Ultra-High Performance Concrete after Exposition to Elevated Temperature

CHEN Meng; Feng Jun; ZHANG Tong

doi:10.3969/j.issn.1007-9629.2025.02.004

Abstract：To investigate the effects of elevated temperature and strain rate on the splitting tensile properties of ultra-high performance concrete(UHPC),the mass loss rate,compressive strength,elastic modulus,static and dynamic splitting tensile tests(strain rate increases from 1.9 s-1 to 6.8 s-1)were carried out at different temperatures(20,105,200,300,400℃).Results reveal that all specimens experienced explosive spalling during the temperature holding period after heating at a rate of 2-10℃/min to 400℃.The compressive strength,elastic modulus and static splitting strength of UHPC increase with the increase of temperature,and the strength of UHPC at 300℃increases by 13.2%,19.1%and 17.3%,respectively,relative to that at room temperature.The dynamic splitting strength and dissipated energy show an obvious strain rate effect.When the strain rate increases from about 2.0 s-1 to 6.5 s-1,the dynamic splitting strength and dissipated energy of UHPC increase by 69.1%-74.1%and 146.7%-177.6%,respectively,within the measured temperature range.After exposed to elevated temperatures,the adsorbed water on C-S-H gel surface,the free water in pores and the gel-bound water in UHPC are gradually decomposed,result in increase of the mass loss rate of UHPC.The high-temperature and high-pressure environment in UHPC matrix promotes cement hydration reaction and pozzolanic reaction,improving the density of UHPC matrix and the bridging effect of steel fiber.At the higher strain rate,the crack propagation in UHPC specimen is faster and the friction effect of steel fiber pulling out is enhanced,which leads to the increase of dissipated energy.