Evaluation and prediction of long-term tensile behavior of glass fiber-reinforced polypropylene bars applied in sea-water sea-sand concrete

The long-term tensile behavior of glass fiber-reinforced polypropylene (GFRPP) bars immersed in saline solution (SS) and saline-alkaline solution (SAS) was experimentally and theoretically investigated. Three temperatures (25, 40, and 60 ℃) and three ages (4, 8, and 12 weeks) were considered for long-term tensile tests . The results revealed that using prepreg tape preparation led to bar defects like micro-voids, micro-cracks, and inadequate fiber impregnation which increased water absorption. Elevated temperatures accelerated interfacial debonding and void expansion as the primary degradation mode. Tensile strength and elongation were significantly affected by corrosion solution, temperature, and age while elastic modulus had minimal impact. After 12 weeks of conditioning in SS and SAS, the strength retentions were 85.3 % and 57.4 % at 25 ℃ respectively; at 60 ℃, they were 36.5 % and 22.3 %, respectively. Resin softening and interfacial debonding caused fiber straightening and premature rupture of local fibers. For the SAS condition, leaching, etching, and embrittlement accelerated interfacial debonding and fiber degradation , causing worse tensile degradation. Based on the Arrhenius theory, the strength retention in SS dropped to 30 % after 6.2, 3.4, and 2.4 years at 5.7, 14.0, and 20.3 ℃, respectively. Similarly, the strength retention in SAS decreased to 30 % after 1.2, 0.8, and 0.6 years. ● Water absorption properties of GFRPP bars in corrosive solutions were revealed. ● Long-term tensile behaviors of GFRPP bars were studied experimentally and theoretically. ● Mechanisms of water absorption and tensile degradation were clarified.