This paper explores the feasibility of improving the spalling resistance and maintaining the compressive strength of ultra-high performance concrete(UHPC)under high temperatures by adding polypropylene fibers through methods such as direct observation,experimental testing,and microstructural analysis.The study shows that conventional UHPC specimens begin to spall at approximately 350℃,accompanied by a sharp decline in compressive strength.A low polypropylene fiber content(e.g.,0.1%)can inhibit the occurrence of spalling.Under the temperature range from room temperature to 400℃,only microcracks appear on the surface of the specimens,and the compressive strength increases with the increase of the fiber content.When the temperature is higher than 400℃,the compressive strength gradually decreases,but the overall reduction is significantly lower than that of ordinary UHPC.Within the temperature range from room temperature to 800℃,a polypropylene fiber content of 0.2%demonstrates the best performance in terms of spalling resistance and compressive strength retention.Scanning electron microscopy-based microstructural observations indicate that the differential thermal expansion coefficient and incompatibility between polypropylene and steel fibers create microcracks,enhancing internal connectivity and effectively releasing internal steam pressure,thereby improving the spalling resistance of the UHPC specimens.
关键词
超高性能混凝土/聚丙烯纤维/高温环境/强度退化/爆裂
Key words
ultra-high performance concrete/polypropylene fiber/high temperature environment/strength degrada-tion/spalling
维普
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