Li Huayun, Chen Bingguang, Zhu Kaicheng, Gong Xiaolin
School of Architecture and Civil Engineering, Xihua University, Chengdu 610039, China.
School of Emergency Management, Xihua University, Chengdu 610039, China.
Materials (Basel). 2022 Jul 22;15(15):5103. doi: 10.3390/ma15155103.
Steel fibers are widely used because they can effectively improve the tensile, compressive and flexural properties of concrete structures. The selection of steel fiber dosage and aspect ratio at high temperature has an important impact on the flexural toughness of concrete components post-fire. In this paper, discussions are made on the simulated fire test in compliance with the ISO 834 standard to study the steel fiber-reinforced concrete (SFRC) components post-fire. The research reveals the influence of two commonly used steel fiber aspect ratios (50, 70) and steel fiber dosages (30 kg/m, 40 kg/m, 45 kg/m) on the changes of the internal temperature field, the initial crack flexural strength and the flexural toughness of the SFRC components under a single-side fire. Moreover, combined with the four-point flexural test of the SFRC components post fire, the research also describes the damage of high temperatures to the flexural toughness of SFRC components, and suggests a calculation formula for SFRC thermal conductivity by way of the numerical inversion method. The results of this study have verified that the incorporation of steel fiber into concrete helps to reduce its internal thermal stress difference and improve the crack resistance and fire resistance of the concrete. Moreover, under high temperature conditions, the concrete component added with the steel fiber in an aspect ratio of 70 and a dosage of 45 kg/m increased their initial crack flexural strength by 56.8%, higher than that of plain concrete components, and the loss of equivalent flexural strength and flexural toughness of SFRC post fire was only 45.2% and 13.6%, respectively. The proposed calculation formula of thermal conductivity can provide a reference for a numerical simulation study of the temperature field of SFRC components in a high temperature environment.
钢纤维被广泛应用，因为它们能有效改善混凝土结构的抗拉、抗压和抗弯性能。高温下钢纤维用量和长径比的选择对火灾后混凝土构件的抗弯韧性有重要影响。本文针对符合ISO 834标准的模拟火灾试验展开讨论，以研究火灾后钢纤维增强混凝土（SFRC）构件。研究揭示了两种常用钢纤维长径比（50、70）和钢纤维用量（30 kg/m、40 kg/m、45 kg/m）对单面火灾下SFRC构件内部温度场变化、初裂抗弯强度和抗弯韧性的影响。此外，结合火灾后SFRC构件的四点弯曲试验，该研究还描述了高温对SFRC构件抗弯韧性的损伤，并通过数值反演方法给出了SFRC导热系数的计算公式。本研究结果验证了在混凝土中掺入钢纤维有助于降低其内部热应力差，提高混凝土的抗裂性和耐火性。此外，在高温条件下，长径比为70、用量为45 kg/m的钢纤维增强混凝土构件的初裂抗弯强度提高了56.8%，高于素混凝土构件，火灾后SFRC的等效抗弯强度损失和抗弯韧性损失分别仅为45.2%和13.6%。所提出的导热系数计算公式可为高温环境下SFRC构件温度场的数值模拟研究提供参考。
