Low temperature behavior of braided aramid fiber bars/concrete interface
Résumé
Braided aramid fiber bars (BAFB) are being used for the reinforcement of concrete structures for more than ten years. Their main advantages over classical steel rebar rely in their lightness, durability performances, mechanical properties, and electromagnetic neutrality. A potential application is the construction of no-maintenance reinforced concrete structures for low temperature or cryogenic environments (Arctic regions or LNG facilities for instance), but the durability of BAFB reinforced concrete is still to be demonstrated in such extreme conditions. In this context, this study aims at investigating the low temperature behavior (-50°C) of the BAFB/concrete materials. A first series of pull-out experiments conducted at ambient temperature made it possible to assess the bond stress-slip responses of various BAFB reinforced specimens and the influence of several key parameters (diameter and surface treatment of the bars). Similar experiments were then carried out at low temperature in order to evaluate the effect of differential dilatations of the constitutive materials (concrete and BAFB rebars) on the bond properties. The last part introduces a theoretical modeling of the pull-out tests at low temperature using a finite element code. Numerical simulations were performed taking into account the actual thermal expansion coefficients of the BAFB bars, which were previously determined by dilatometric characterizations. Complementary studies are needed for the perfect suitability of braided aramid fiber rebars in cold environments but the presented results show good prospects for such applications and provide valuable data for future design procedures.