Fiber reinforced polymer bar investigation: Long-term in-situ durability and bond strength assessment in conventional and sustainable concrete

Corrosion of steel reinforcement and carbon dioxide emissions are two major global problems. Different methods, techniques, and materials have been implemented to mitigate these problems. Glass fiber-reinforced polymer (GFRP) bar presents itself as a solid alternative to replace conventional steel reinforcement owing to its fantastic features in resisting corrosion. Its demand is progressively increasing. Cement-based concrete, on the other hand, is not eco-friendly due to the excessive amount of carbon dioxide (CO2) emissions yielded from its cement production. One of the alternatives used to mitigate the use of cement in concrete is fly ash. Fly ash is considered a supplementary cementitious material (SCM) and has been only implemented partially to replace cement as a binding material in concrete, however its application has been limited to only limited doses (lower than 30%). In this study, durability and bond-slip investigations were carried out. The durability study was done on GFRP bars extracted from eleven bridges across the United States after being in service from 12 to 20 years. Several tests were conducted on the bar and the surrounding concrete to make the assessment. The tests results showed that there were slight sings for environmental attack but did not show any obvious signs for microstructural deteriorations. In addition, a bond-slip investigation was carried out to evaluate the bond performance of GFRP bars embedded in fly ash-based sustainable concrete. A high-volume fly ash (HVFA) concrete was implemented; 50% and 70% cement replaced with fly ash were used. The results showed that GFRP bars had less bond strength than that resulted from mild steel bars --Abstract, page iv