31 / 2022-03-13 05:56:31

Preventive effect of fire spalling of the prestressed concrete beam with natural jute fiber

prestressed concrete beam, ring restraint specimen, fire spalling, Jute fiber, PP fiber

Prestressed concrete (PC) structures have the advantage of resisting tensile stress and preventing cracking because of the initial compressive stress.  However, PC structures have a higher risk of fire spalling compared to reinforced concrete (RC) structures due to the pre-stressing force.  There are two theories on the mechanism of fire spalling: thermal stress theory and water vapor pressure theory, and their combined theory.  The method of fire spalling evaluation of concrete is standardized by the Japan Concrete Institute. Recent papers reported reducing fire spalling of concrete with synthetic fibers such as PP fibers. On the other hand, our research group investigated to prevent fire spalling by natural jute fiber. Jute fibers are sustainable materials. However, it is not reported the effect of Jute fibers on the suppression of fire spalling in PC beams. In this study, heating tests were conducted on PC beams with Jute fibers and PP fiber to investigate the effect of suppressing fire spalling. Additionally, ring restrained specimens were made with the same mixture as the PC beams and were subjected to heating tests. And we evaluated fire spalling depth, restrained stress, and vapor pressure. 

As a result, the effect of fire spalling suppression was confirmed for both PP and Jute fiber.

In addition, the fire spalling depths of the ring-restrained specimens were similar to those of the PC beams.