Abstract Guaranteeing the integrity of tunnel structures during and after fire is key in support of a sound fire safety strategy and for minimizing the risk of disruption in the operation of the tunnel due to restauration works post-fire. Innovations in concrete technology have enabled what is known as Fibre Reinforced Concrete (FRC); where very small fibres are used to substitute traditional reinforcement inside concrete. Within the scope of this study, the fire behaviour of a specific type of FRC including a combined dose of macro and micro polypropylene (PP) fibres is studied in depth. Experimental investigations were performed to study (1) the occurrence of fire-induced concrete spalling and (2) the integrity of macro PP fibres after cooling. Fire tests were performed using an H-TRIS test method set to condition concrete test samples to have an in-depth temperature gradient equivalent to that modelled for identical concrete under the Hydrocarbon curve in a standard furnace. Test results show that the time-to-spalling was directly influenced by the presence of macro and micro PP fibres; spalling happened earlier for concrete samples containing PP fibres. This study showed that macro PP fibres remained intact after cooling for depths where concrete was below the 300 °C threshold.

中文翻译：

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隧道用纤维混凝土防火性能试验研究

摘要 在火灾期间和之后保证隧道结构的完整性是支持健全的消防安全策略和最大限度地减少火灾后修复工程造成隧道运营中断风险的关键。混凝土技术的创新实现了所谓的纤维增强混凝土 (FRC)；使用非常小的纤维代替混凝土内部的传统钢筋。在本研究的范围内，深入研究了特定类型的 FRC 的防火行为，包括组合剂量的粗纤维和微型聚丙烯 (PP) 纤维。进行了实验研究以研究 (1) 火灾引起的混凝土剥落的发生和 (2) 冷却后大 PP 纤维的完整性。使用 H-TRIS 测试方法进行火灾测试，该方法设置为调节混凝土测试样品，使其具有与标准炉中碳氢化合物曲线下相同混凝土模拟的深度温度梯度等效的深度温度梯度。测试结果表明，散裂时间直接受粗PP纤维和微细PP纤维的影响；对于含有 PP 纤维的混凝土样品，剥落发生得更早。该研究表明，在混凝土低于 300 °C 阈值的深度冷却后，宏观 PP 纤维保持完整。对于含有 PP 纤维的混凝土样品，剥落发生得更早。该研究表明，在混凝土低于 300 °C 阈值的深度冷却后，宏观 PP 纤维保持完整。对于含有 PP 纤维的混凝土样品，剥落发生得更早。该研究表明，在混凝土低于 300 °C 阈值的深度冷却后，宏观 PP 纤维保持完整。