Fire Resistance Tests on Prestressed Concrete Box Girder with Intumescent Fire-Retardant Coatings

The fire resistance of prestressed concrete (PC) structures is seriously affected due to the sensitivity of these structures and significant damage to high temperature. With the continuous improvement of the fire resistance rating of the structures, the fire resistance of PC structures has attracted much attention. According to the relevant research, the reasonable fire protection and heat insulation measures can effectively improve the fire resistance of the PC structures and meet requirements of the fire resistance rating. However, very limited research has been conducted on the effect of intumescent fire-retardant coating (IFC) on the fire resistance of PC structures. Hence, the fire resistance of PC box girder coated with IFC is studied in this paper. Under the combined thermal load and external load, the appearance, thermal response, deflection, prestress variation and fire resistance of the structures under high temperature are measured and compared. The effect of IFC on the fire resistance of PC box girder is preliminarily studied. The test results showed that the IFC can effectively reduce the spalling, bursting and cracking of concrete, effectively prevent concrete structure of reaching very high temperature, significantly reduce the deflection of PC structure at high temperature, and effectively protect the structural prestress. The fire resistance of PC structures can be effectively improved by adopting IFC. In addition, it is found that the fire resistance of PC box girder with high flexural rigidity may be determined by its ultimate bearing capacity rather than its ultimate deflection to high temperature.