Durability assessment of GFRP bars in concrete exposed to field environment based on interlaminar shear strength

The interlaminar shear strength (ILSS) can be an indicator of the deterioration of glass fibre-reinforced polymer (GFRP) bars. This property is normally evaluated by using a sample with a length equal to four to seven times the bar diameter, which can be extracted from in-service structures. First, this study conducted an intensive review to establish the relationship between tensile strength (TS) and ILSS retentions of vinyl-ester based GFRP bars, including the effect of sustained stress. TS and ILSS retentions show 0.18–0.92 and 0.30–0.92, respectively, when fibre, resin, and fibre-resin interface damage is observed near the exposed surface. This relationship demonstrates the applicability of assessing the durability of GFRP bars based on ILSS. Available ILSS retentions range from 0.71 to 0.93 on the field durability of GFRP bars extracted from 11- to 20-year-old bridge barriers, bridge decks, a dry-dock, and exposed bars. The reported field durability is compared with a prediction model established from laboratory immersion tests for GFRP bars embedded in concrete. It is shown that predictions based on the immersion in tap water or saline solution in the laboratory can explain the reduction in ILSS of GFRP bars extracted from actual structures while a prediction based on the immersion in alkaline solution is conservative.