A multi-level factor interaction framework of fire-induced spalling of cementitious material based on a systematic review

Fire-induced concrete spalling under high temperatures is a complex phenomenon that affects the safety of reinforced concrete structures in fire. However, there have been few attempts to comprehensively review or systematically analyze the results of existing studies, which cover different types of concrete and different influencing factors. Hence there is no consistent understanding of the mechanism of fire-induced concrete spalling that can be applied across the range of types of concrete. This study provides a critical review of the fire-induced concrete spalling mechanism, covering ordinary concrete (OC), fibre-reinforced concrete (FRC), ultra-high performance concrete (UHPC), ultra-high toughness cementitious materials (UHTCC) and engineered cementitious composite (ECC). The reviewed research results are summarized in the context of a multi-level factor interaction framework (MFIF), in which the influencing factors and parameters of fire-induced concrete spalling are de-coupled and ranked into two levels on the basis of causality. The first-level factors include water/cement ratio (W/C), fibres, moisture content, aggregate, geometric characteristics, heating conditions and mechanical conditions. These factors can be directly manipulated in the design of concrete material. The second-level parameters include material high-temperature strength, pore pressure, thermal stress and mechanical stress. These parameters are directly influenced by the factors in the first level and, if linked with the classic theories of fire-induced concrete spalling to form a spalling criterion that considers the whole range of influencing factors. This review aims to help understanding the nature of fire-induced concrete spalling in a systematic fashion, with the aims of assisting in the design of spalling-inhibiting concrete materials and providing guidance on fire-induced concrete spalling criteria for numerical simulations.