Tensile and interlaminar shear behavior of thermoset and thermoplastic GFRP bars exposed to alkaline environment

Glass fiber-reinforced polymer (GFRP) bars have been increasingly employed as an alternative to traditional steel bars to reinforce concrete members exposed to harsh environments. GFRP bars do not suffer corrosion, have a tensile strength higher than that of steel reinforcing bars, and an elastic modulus 20–25% of that of steel reinforcing bars. Although bars comprising thermosetting resin are the most diffused, thermoplastic resin bars have been recently proposed to overcome some sustainability and durability drawbacks related to the use of thermosetting resins. Glass fibers may be strongly degraded in alkaline environments, such as in concrete members where the high pH (i.e., approximately 12–13) seriously threaten the effectiveness of both thermoset and thermoplastic GFRP reinforcing bars. For this reason, and considering the limited research available in the literature on thermoplastic bars, experimental tests are fundamental to verify the durability of GFRP bars exposed to alkaline environment. In this paper, tensile and interlaminar shear tests of GFRP bars comprising E-glass fibers and thermoset and thermoplastic resin are presented. Results of specimens immersed in an alkaline solution are compared with corresponding results of control specimens. Three different diameters are considered for each type of bar, i.e., thermoset and thermoplastic bars. Tests are conducted according to ISO 10406–1 and ASTM D4475 and show that, although a limited effect of the alkaline conditioning was observed, the bar diameter and type of resin affected the tensile and interlaminar properties of the conditioned GFRP bars studied.