Durability of BFRP bars embedded in geopolymer concrete under hygrothermal exposure and sustained loading

The long-term durability of basalt fiber-reinforced polymer (BFRP) bars embedded in fly ash-slag blended geopolymer concrete was investigated under various hygrothermal exposure conditions and sustained loading. Experimental testing revealed critical insights into the relationship between environmental conditions and BFRP bars deterioration. Results demonstrated that the most significant reduction in tensile strength of 81.5 % occurred under sustained loading of 25 % of the ultimate tensile strength (UTS) at 40°C for 9 months. FTIR and SEM analyses confirmed that the hydrolysis reaction was exacerbated by sustained loading, causing fiber delamination, matrix disintegration, and interfacial debonding. DSC results indicated a substantial reduction in glass transition temperature (Tg) due to a reversible plasticization effect. Conditioning at 40–60°C caused the most damage to the BFRP bars, with high moisture uptake and low retained tensile strength. Collected data from accelerated aging experiments were also used to develop master curves to predict the service life of BFRP bars embedded in geopolymer concrete. The experimental findings provide a robust and reliable approach for assessing the durability performance of FRP composites embedded in geopolymer concrete.