Repair and strengthening of CFRP-wrapped lightweight concrete exposed to elevated temperatures

Lightweight concrete has proven effective material due to its high strength-to-weight ratio, cost-effectiveness, improved sound insulation, and fire resistance. However, there is scarce data on the confinement behaviour of the lightweight concrete (LWC) exposed to elevated temperatures, particularly when wrapped with fiber-reinforced polymers (FRP). This study explores the behaviour of LWC strengthened and repaired with carbon FRP (CFRP) laminates tested under elevated temperatures. LWC specimens wrapped with CFRP laminates are tested experimentally under temperatures varying from 20 °C to 800 °C. Parameters like compressive strength, stress-strain behaviour, elastic modulus, and failure modes are evaluated as a function of increasing temperature. Analytical models are developed to estimate the degradation on compressive strength and elastic modulus with temperature and validated against experimental data. The outcomes from this study support the use of CFRP wraps to partially restore the strength and elasticity in LWC compression members at moderate temperatures, enhancing its resilience in fire-prone applications. • CFRP-wrapped specimens failed due to rupture of concrete. • Compressive strength in CFRP-strengthened LWC dropped significantly beyond 400 °C. • CFRP wrapping enhanced the modulus of elasticity, but it reduced at higher temperatures. • CFRP-repaired LWC outperformed CFRP-strengthened LWC at elevated temperatures. • Analytical models were developed to predict compressive strength and modulus of elasticity.