Short-term durability of GFRP stirrups under wet-dry and freeze–thaw cycles

GFRP stirrups are a promising alternative to conventional steel stirrups due to their non-corrosive nature. However, their performance under cyclic exposure to wet-dry and freeze–thaw conditions in seawater needs to be evaluated to ensure their long-term durability and sustainability. This study investigates the tensile strength of glass fibre reinforced polymer (GFRP) stirrups under seawater wet-dry cycles and seawater and tap water freeze–thaw cycles. In total, 220 stirrups in two different shapes, i.e. U and L shapes, and two different diameters, i.e. 6 mm and 8 mm were manufactured, conditioned, and tested under stirrup tensile test. Conditioned stirrups were subjected to 9 months and 18 months wet-dry cycles in seawater at 25 ℃, 40 ℃, and 60 ℃, and 9 months and 18 months freeze–thaw cycles in seawater and tap water. At first, the samples underwent a fast deterioration rate, which then decreased as the conditioning period progressed from 9 months to 18 months. The strength retention values of L-shaped stirrups were found to be higher than those of U-shaped stirrups, regardless of the environmental conditions or diameter. The maximum tensile strength reductions of 31%, 28% and 16% were observed, respectively after exposure to 18 months conditioning in seawater wet-dry cycles at 60 ℃, freeze–thaw in seawater, and freeze–thaw in tap water.