Fire spalling behaviour of heat-resistant repair materials under ring restrained condition

When repaired RC structures are exposed to fire, there is a risk of fire spalling, as in the case of concrete.Our group previously investigated the fire spalling behavior of cement materials using ring-restrained heating tests and developed heat-resistant repair materials (HRM) that can be used within an application range of 300 or less.However, we have not yet examined whether the HRM materials can be applied at temperatures above 300 .In this study, we evaluated the fire spalling behavior of HRM using a ring-restrained heating test, and a small cylindrical electric furnace was used.In addition, the effect of jute fibers on the fire spalling prevention of repair mortar was examined.In a results, the maximum fire spalling depth of the Control specimen was 12 mm, and the fire spalling suppression effect on HRM was confirmed by mixing more than 0.1 vol% of Jute fiber.We discussed the relationship between the restrained stress, vapor pressure, and internal temperature at 5 mm from each specimen.Vapor pressure increased to 8 MPa at 140 for the control specimen, and fire spalling occurred.The restrained stress was 4 MPa at 140 .For the jute specimens, the maximum restrained stress ranged from 2 to 3 MPa, and the restrained stress of the jute specimen was lower than that of the control specimen.The maximum vapor pressure in the jute specimens was approximately 11 MPa.Although the maximum vapor pressure of the jute specimen was higher than that of the control specimen, no fire spalling occurred.