Long-term performance of glass fiber-reinforced polymer reinforcement embedded in concrete

The chemical reactions that occur in glass fiber-reinforced polymer (GFRP) bars when embedded in concrete result in reduced tensile capacities of the bars over time. ACI recognized this and places reduction factors on the allowable design strength of GFRP reinforcing bars. There are limited longer-term data on GFRP bars embedded in concrete available, however, and probabilistic models based on GFRP bars embedded in concrete are not available to validate these reduction factors. This study investigated GFRP reinforcing bars embedded in concrete and exposed to unsubmerged conditions for 7 years. The results indicate lower rates in the loss of capacity when compared with data from the literature on accelerated exposure. Linear deterministic models indicate that the ACI reduction factors may be unconservative, but these models are likely too simple to represent real conditions. Probabilistic models to assess the time-variant capacity of GFRP bars embedded in concrete to better assess the capacity loss and ACI design reduction factors for GFRP reinforced structures are needed.