Reinforcing concrete members with fibre-reinforced polymer (FRP) rebars, as an alternative to common corrosion-prone steel rebars, is steadily increasing, leveraging on their potential to ensure longer structural service lives. Another boost will come from the second generation of Eurocode 2, which for the first time includes supplementary guidance for the design of new structures with non-prestressed glass and carbon fibre reinforcement. Several technological developments are ongoing to optimize the performance of FRP rebars, namely regarding their surface and bond-slip response. This topic is investigated herein via an experimental program focusing on two complementary aspects: (i) the influence of various surface conditions on the bond stress-slip behaviour of glass FRP (GFRP) rebars with thermoset and thermoplastic polymers; machine-coated and helically-wrapped sand-coated surfaces are included, as well as newer approaches to surface treatment such as peel-ply and peel-ply/grid; (ii) the influence of different embedment lengths, namely 10×, 20×, and 30× the rebar diameter, on the pull-out response of GFRP rebars with a yet-distinct surface treatment known as calendering; this paper briefly shows and discusses the evolution of strains along the three embedment lengths up until pull-out failure, as obtained from distributed optical fibre sensors, which is another novelty.
Almeida et al. (Wed,) studied this question.