Strengthening of fiber-reinforced geopolymer concrete after high-temperature exposure using CFRP sheets

The manufacturing of Portland cement contributes to 5–8% of global CO₂ emissions. Therefore, there has been considerable emphasis on using environmentally friendly building materials. Geopolymer concrete (GPC) is an eco-friendly material, and the addition of fibers can reduce its brittleness and improve its overall performance, offering considerable potential for many structural applications. However, the structural integrity and lifespan of reinforced concrete structures are significantly diminished by fire. The current study investigates the strengthening of fiber-reinforced GPC after high-temperature exposure using carbon-fiber-reinforced polymer (CFRP) sheets. Three GPC mixes were evaluated, which included steel fibers and polyvinyl alcohol fibers with 1 vol%. Strengthening by CFRP wraps was evaluated for GPC specimens following exposure to temperatures of 25 and 500°C. This study conducts experimental testing involving a total of 36 cylinders at 28 curing days, each measuring 100 mm in diameter and 200 mm in height. The results indicate that the heated specimens exhibited a significant reduction in compressive strength up to 72.0% compared to the unheated specimens. The strengthening of heated specimens by application of CFRP wrap increased the compressive strength up to 105.2% compared to unstrengthened specimens subjected to 25°C. Therefore, the original compressive strength was restored by strengthening heated GPC specimens using CFRP wraps.