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Glass Fibre Reinforced Polymer (GFRP) bars are now attracting attention as an alternative reinforcement in concrete slabs because of their high resistance to corrosion that is a major problem for steel bars. Recentlyhollow concrete slab systems are being used to reduce the amount of concrete in the slab and to minimise the self-weight, but the internal holes makes them prone to shear failure and collapse. A hollow composite reinforcing system (CRS) with four flanges to improve the bond with concrete has recently been developed to stabilise the holes in concrete members. This study investigated the flexural behaviour of concrete slabs reinforced with GFRP bars and CRS. Four full-scale concrete slabs (solid slab reinforced with GFRP bars; hollow slab reinforced with GFRP bars; slab reinforced with GFRP bars and CRS; and slab reinforced with steel bars and CRS) were prepared and tested under four-point static bending to understand how this new construction system would perform. CRS is found to enhance the structural performance of hollow concrete slabs because it is more compatible with GFRP bars than steel bars due to their similar modulus of elasticity. A simplified Fibre Model Analysis (FMA) reliably predicted the capacity of hollow concrete slabs. [ABSTRACT FROM AUTHOR]

• Carbon fiber reinforced polymer. • Tensile strength. • Glass transition temperature. • Curing conditions. • Bond on concrete. Polymeric adhesives are widely used for the bonding of carbon fibre-reinforced polymers (FRPs) on a concrete structure. Structural reinforcement using FRPs is a very efficient strategy owing to the good mechanical characteristics of FRPs and the implementation methods, which are applied onsite and make it possible to reduce the work time. Efficiency is limited by FRP debonding and adhesive has a key issue to play in the strengthening. Working onsite assumes that the conditions for implementation are highly dependent on the climate. In this context, it should be noted that the resins used are cold-curing epoxy and that their mechanical and physical properties are temperature- and humidity-dependent. In this study, the impact of the application temperature on the behaviour of composite reinforcement is investigated. The objective is to analyse the mechanical and physical behaviour of epoxy polymers used for reinforcement by measuring the mechanical properties of composite adhesion on a concrete support via double-shear and pull-out tests, as well as the glass transition temperatures Tg. The Tg measurements are performed using differential scanning calorimetry and thermomechanical analysis. Double-shear tests are performed to establish the local composite-to-concrete shear laws for adhesive joints according to the nature of the polymers and the curing conditions. The test results allow for determination of the bonding length (Le) and its dependence on the curing conditions. The physical measurements of Tg support the study by elucidating the influence of the curing conditions on these properties. [ABSTRACT FROM AUTHOR]

Carbon-based nanoparticles (CBNs) are regarded as promising nanofillers in nanocomposites to produce high-performance fiber-reinforced polymers (FRPs). To date, no systematic investigations have been carried out on the structural variations of nanofillers and their influences on dispersion characteristics, which give nanocomposites their mechanical and durability properties. Moreover, environmentally unfriendly organic solvents are used to exfoliate and disperse CBNs in a polymer matrix. This study developed a green, easy approach to preparing epoxy/CBN nanocomposites. We demonstrated graphene oxide's (GO) effective dispersion capacity, creating good interface interaction that dramatically influenced properties at loadings as low as 0.4 wt%. The tensile strength and toughness of the epoxy increased by about 49%; and 160%, respectively. Incorporating 0.4 wt% of multi-wall carbon nanotubes (MWCNTs), graphene nanoplates (GNPs), or GO into the epoxy increased the modulus storage by around 17%, 25%, and 31%, respectively. Fractography analysis of fracture surfaces indicated the primary reinforcing mechanisms (crack deflection and penning) as well as the secondary mechanism (bridging effect) enhancing the mechanical characteristics of nanocomposites. Incorporating GNPs, GO, or MWCNTs into the epoxy decreased the water absorption at saturation by about 26%, 22%, and 16%, respectively.