Durability of bond between EBR-CFRP laminate and concrete after four years of natural outdoor and accelerated ageing exposures

Application of carbon fibre reinforced polymer (CFRP) composites in strengthening of existing reinforced concrete (RC) structures has been widely accepted. However, the durability of adhesively bonded CFRP-concrete joint has not yet been fully investigated, which therefore paves the way to the topic addressed in this work: the durability of the joint in concrete elements strengthened with CFRP laminate using externally bonded reinforcement (EBR) technique. Concrete strengthened elements were kept in laboratory-controlled environments (approximately 20 °C/55 % RH, and water immersion at 20 °C), while others were kept outdoor to mainly promote natural ageing by carbonation, high temperatures, freeze-thaw attacks, and airborne chlorides. The results from durability tests after 4 years of exposure showed insignificant bond strength degradation but with a noticeable bond stiffness reduction, also, the stiffness degraded faster than the strength. Besides, environmental conversion factors of 0.75 and 0.95 were derived from a database of existing accelerated ageing test data and the natural ageing test data from the present work, respectively.