Spalling Resistance of Fiber-Reinforced Ultra-High-Strength Concrete Subjected to the ISO-834 Standard Fire Curve: Effects of Thermal Strain and Water Vapor Pressure

• Main Authors: Taegyu Lee, Gyuyong Kim, Gyeongcheol Choe, Euichul Hwang, Jaesung Lee, Dongwoo Ryu, Jeongsoo Nam
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Materials
• Subjects: ultra-high-strength concrete; thermal stress; water vapor pressure; ISO-834 standard fire curve; pore formation; fiber melting
• Online Access: https://www.mdpi.com/1996-1944/13/17/3792

The prevention and mitigation of spalling in high-strength concrete (HSC) rely on mixing polypropylene (PP) as an additive reinforcement. The dense internal structures of ultra-high-strength concrete (UHSC) result in risks associated with a high thermal stress and high water vapor pressure. Herein, the effects of pore formation and thermal strain on spalling are examined by subjecting fiber-laden UHSC to conditions similar to those under which the ISO-834 standard fire curve was obtained. Evaluation of the initial melting properties of the fibers based on thermogravimetric analysis (TGA) and differential thermal analysis (DTA) demonstrated that although nylon fibers exhibit a higher melting point than polypropylene and polyethylene fibers, weight loss occurs below 200 °C. Nylon fibers were effective at reducing spalling in UHSC compared to polypropylene and polyethylene fibers as they rapidly melt, leading to pore formation. We anticipate that these results will serve as references for future studies on the prevention of spalling in fiber-reinforced UHSC.