Effects of Immersion in Water, Alkaline Solution, and Seawater on the Shear Performance of Basalt FRP Bars in Seawater-Sea Sand Concrete

This article presents an experimental study investigating the long-term shear performance of basalt fiber-reinforced polymer (BFRP) bars wrapped in seawater-sea sand concrete (SSC) immersed in different solution environments. Horizontal shear tests and transverse shear tests of immersed bare and SSC-wrapped BFRP bars were conducted. The various tested parameters included the following: (1) SSC wrapping thickness (0, 10, and 20 mm); (2) solution environment (alkaline solution, seawater, and tap water); (3) immersion time (15, 30, 90, 180, 360, and 540 days); and (4) conditioning temperature (similar to 26 degrees C, 40 degrees C, and 60 degrees C). In addition, the test findings of the durability of BFRP bars wrapped with SSC were compared with those wrapped with conventional concrete. The results showed that alkalinity is the main factor controlling the performance degradation of BFRP, and the degradation of BFRP is strongly correlated with the concrete wrapping size (the greater the wrapping thickness is, the greater the degradation is). SSC leads to a higher pH of the immersion solutions and combines the reaction of the Na+ and K+ contained in the sea sand and silica of the basalt fibers, resulting in the shear strength retention of BFRP bars wrapped with SSC being lower than that of bars wrapped with conventional concrete under the same conditions.