School of Civil Engineering, Harbin Institute of Technology
China Construction Eighth Engineering Division Co. Ltd

采用直观观察、试验测试和微观特征分析的方法,探索通过掺加聚丙烯纤维改善超高性能混凝土(UHPC)高温环境下爆裂行为和维持压缩强度的可行性。研究表明,常规UHPC试件在350℃左右开始发生爆裂并伴随抗压强度的急剧降低。聚丙烯纤维掺量较低(如0.1%)时,即可抑制爆裂现象的发生。室温至400℃加载范围内,试件表面仅出现微裂纹,随着纤维用量的增加,抗压强度随之增加;超过400℃后,抗压强度逐渐下降,但整体下降幅度明显低于普通UHPC材料。室温至800℃的加载范围内,聚丙烯纤维掺量0.2%时,试件表现出最优的抗爆裂性能和抗压强度的维持能力。基于扫描电镜的微观结构观察表明,聚丙烯纤维和钢纤维因热膨胀系数的不同和热不相容性产生的微裂纹增加了材料内部的连通性,有效释放了内部蒸汽压力,从而提升了试件的抗爆裂性能。

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 ℃, 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 ℃, 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 ℃, 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 ℃, 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.

“十四五”国家重点研发计划项目(2022YFC3801101);中建股份科技研发计划项目(CSCEC-2022-Z-19)