Residual properties of ultra-high performance concrete containing steel-polypropylene hybrid fiber exposed to elevated temperature at early age

Wang, T. and Yu, M. and Tian, J. and Sun, Z. and Yu, C. and Ye, J. (2025) Residual properties of ultra-high performance concrete containing steel-polypropylene hybrid fiber exposed to elevated temperature at early age. Journal of Building Engineering, 99: 111507. ISSN 2352-7102

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Abstract

To investigate residual properties of Ultra-High Performance Concrete (UHPC) containing steel-polypropylene hybrid fiber subjected to fire accidents during construction, uniaxial compressive tests were carried out on UHPC exposed to elevated temperature at early age. The test parameters include the age exposed to elevated temperature, temperature levels, steel fiber content and coarse aggregate content. Based on the test results, failure mode, strength, elastic modulus, peak strain, and strain-stress response of the tested specimens were analyzed. Additionally, microstructures of the specimens were characterized using X-ray diffraction and scanning electron microscopy. The test results show that up to 600 °C, the residual compressive strength of the UHPC generally increases with age due to the improved resistance and accelerated hydration. At 800 °C, the strength decreases slightly with age due to the porosity and carbonation reactions. Finally, an empirical formula was proposed to predict the compressive strength, peak strain, elastic modulus, and the uniaxial compressive stress-strain constitutive model of the UHPC exposed to elevated temperature at early age.