Effectiveness of GFRP strengthening of normal and high strength fiber reinforced concrete after exposure to heating and cooling

Abstract

Damage induced by fire is considered a serious threat to reinforced concrete structures during their useful lifetime. While concrete is a non-flammable material, its exposure to fire affects its stress-strain characteristics and durability. Given that a full replacement and/or demolition option is economically inefficient for fire-damaged structures, a better alternative for lengthening their service life involves repair or strengthening the damaged members. The current testing program primarily investigated the influence of strengthening by glass fiber reinforced polymer (GFRP) sheets on the behavior of heat-damaged plain and fiber-reinforced normal and high strength concretes. Strengthening was considered for concrete cylinders after being exposed to 400 °C and 600 °C temperature and left to cool by air cooling or water quenching. Fiber-reinforced concrete (FRC) mixes were cast with steel, polypropylene, or a hybrid of steel and polypropylene fibers. For plain and various fiber-reinforced normal strength concretes exposed to 400 °C and cooled by ambient air cooling or water quenching, the compressive strength of GFRP confined concrete increased by 39% to 48% and 42% to 56%, respectively (in comparison to the unheated specimens). However, this enhancement was observed to be higher for concretes heated at 600 °C.

Keywords

• GFRP strengthening
• Concrete
• FRC
• Air cooling
• Water quenching
• Elevated temperature