Bond durability and degradation mechanism of GFRP bars in seawater sea-sand concrete under the coupling effect of seawater immersion and sustained load.

• Bond durability of GFRP bars in concrete under immersion and load was investigated. • Degradation mechanism of GFRP bars in concrete was clarified. • Sustained load could accelerate the degradation of the bond performance. • Bond strength after 50 years was predicted according to fib Bulletin 40. In this paper, the bond durability of glass fiber-reinforced polymer (GFRP) bars in seawater sea-sand concrete (SWSSC) under the coupling effect of seawater immersion and sustained load was experimentally investigated. The test parameters included bar diameter (12 and 16 mm), immersion time (90, 180, and 270 days), and sustained load condition (loaded and unloaded). Test results showed that for the specimens with a small bar diameter, the bond strength had a slight growth at the initial stage of exposure mainly due to the water swelling of the bar, and then decreased due to the bond degradation. For the specimens with a large bar diameter, the bond strength increased with the increase of immersion time, which was determined by the increasing compressive strength of SWSSC. The sustained load reduced the bond strength of the specimens with a small bar diameter due to its acceleration of bond degradation, but had little effect on the bond strength of the specimens with a large bar diameter. The degradation mechanism was the rib deterioration of the bars caused by seawater immersion. Moreover, the sustained load could accelerate the degradation. The predicted bond strength retention of the specimen with a bar diameter of 12 mm under the coupling effect of the marine environment (moisture saturated and the mean annual temperature of 25–35 °C) and sustained load is 52% after 50 years of service. [ABSTRACT FROM AUTHOR]