Abstract
The use of fibre reinforced polymers (FRP) as a means of external reinforcement for strengthening the existing reinforced concrete (RC) structures nowadays is the most common technique. However, the use of epoxy resins limits the effectiveness of FRP technique, and therefore, unless protective (thermal insulation) systems are provided, the bond capacity at the FRP-concrete interface will be extremely low above the glass transition temperature (Tg). To address problems associated with epoxies and to provide cost-effectiveness and durability of the strengthening intervention, a new composite cement- based material, namely textile-reinforced mortar (TRM) has been developed the last decade. This paper for the first time examines the bond performance between the TRM and concrete interfaces at high temperatures and, also compares for the first time the bond of both FRP and TRM systems to concrete at ambient and high temperatures. The key parameters investigated include: (a) the matrix used to impregnate the fibres, namely resin or mortar, resulting in two strengthening systems (TRM or FRP), (b) the level of high temperature to which the specimens are exposed (20, 50, 75, 100, and 150 °C) for FRP-reinforced specimens, and (20, 50, 75, 100, 150, 200, 300, 400, and 500 °C) for TRM-strengthened specimens, (c) the number of FRP/TRM layers (3 and 4), and (d) the loading conditions (steady state and transient conditions). A total of 68 specimens (56 specimens tested in steady state condition, and 12 specimens tested in transient condition) were constructed, strengthened and tested under double- lap direct shear. The result showed that overall TRM exhibited excellent performance at high temperature. In steady state tests, TRM specimens maintained an average of 85% of their ambient bond strength up to 400 °C, whereas the corresponding value for FRP specimens was only 17% at 150 °C. In transient test condition, TRM also outperformed over FRP in terms of both the time they maintained the applied load and the temperature reached before failure.
Highlights
Introduction and backgroundThere is a growing need for upgrading the existing reinforced concrete (RC) structures both in seismic and non-seismic areas
This paper investigates experimentally, for the first time the bond between textile-reinforced mortar (TRM) and concrete substrates at high temperatures
The bond strength of 3 and 4 layers fibre reinforced polymers (FRP) specimens was 1.4, and 1.5 times higher than that of counterpart TRM specimens respectively,. This is attributed to the excellent bond between FRP composite and concrete substrate which is confirmed by the amount of concrete being peeled off
Summary
There is a growing need for upgrading the existing reinforced concrete (RC) structures both in seismic and non-seismic areas. This is attributed to deterioration of RC structures as a result of ageing, inadequate maintenance, environmental induced degradation and due to the increase of the applied loads and the need to comply with the modern standards (for example Eurocodes) requirements. A review on the behaviour RC members strengthened with FRPs and subjected to fire or high temperature was recently conducted by Firmo et al [2]
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