Long term durability of pultruded polymer composite rebar in concrete environment

• GFRP rebar was alkaline aged for 24 months at 60 °C.
• Tg and shear strength of the rebar were retained by 91.5%.
• Design tensile strength of the rebar was retained by 100%.
• FT-IR and SEM-EDX findings supported that resin and glass fibres were not degraded.
• Moisture absorption was the critical factor that controlled durability of rebar.

Pultruded glass fibre reinforced polymer (GFRP) composite rebar was immersed in alkaline concrete environment for 0, 1, 2, 3, 4, 6, 14 and 24 months at 60 °C to evaluate its durability in concrete structure. Moisture absorption of the rebar was found to be only 0.76%. It was also found that both the glass transition temperature (Tg) and the short beam shear strength were retained by about 91.5%; and the above properties were remained almost unchanged during the ageing period from 1 month to 24 months. Design tensile strength and tensile elastic modulus of the rebar were retained by 100% after 24 months exposure in concrete environment. Degradation of GFRP rebar was not evident in the FT-IR results as supported by scanning electron micrographs and energy dispersive X-ray analysis. Moisture absorption was found to be a critical factor that controlled thermal and mechanical properties of GFRP rebar.