In the past, research on the use of FRP in civil engineering has been focused on strengthening existing structures where FRP reinforcements were applied to the surface of concrete elements. Recently, the application of FRP reinforcements has been studied to replace steel reinforcements for use in areas of increased environmental loads, with a need to exclude the corrosion of the reinforcement or to ensure the electromagnetic neutrality of the individual elements of the load-bearing structure. The GFRP reinforcement ratio was verified considering failure modes in flexure and the bond of the GFRP reinforcement with concrete. Besides classical reinforcements, GFRP has also been used in prestressed variants, and the possibility of its use as permanent formwork has been verified. In terms of extending the use of non-metallic reinforcements, it is important to note the long-term exposure and possible degradation of the mechanical properties.
Corrosion of steel reinforcement is the major cause of deterioration of existing RC structures. Combined effects of moisture, temperature, and chlorides reduce the alkalinity of concrete and exacerbate the corrosion of steel reinforcement, especially for concrete structures subjected to aggressive environments, such as marine structures and bridges and parking garages exposed to de-icing salts. Glass fiber reinforcement polymer (GFRP) bars are suitable alternatives to steel bars in reinforced concrete applications if durability, electromagnetic transparency, or ease of demolition in temporary constructions is sought, that have to be demolished partially by tunnel boring machines (TBMs). The bond of GFRP reinforcement is different from steel reinforcing bars. This paper presents factors affecting the bond strength between GFRP reinforcement and concrete.
Corrosion of steel reinforcement is one of the most often deterioration reasons of RC structures. At present, the corrosion of steel reinforcement can be avoided by using non-metallic reinforcement from composite materials, especially in structures that are exposed to extreme environmental environment. These materials are durable and non-conductive. They are composited from two materials: fibres and matrix. The most commonly used FRP (Fiber Reinforced Polymers - FRP) reinforcement are glass fibre reinforced polymers (GFRP). The bar surface can be e.g. sanded, wrapped, with helically wound ribs. The bond between concrete and reinforcement is one of the basic requirements for the composite action of both materials. The transfer of forces between the steel reinforcement and the concrete is provided by the following mechanisms: adhesion, friction and mechanical interlocking. The bond between GFRP reinforcement and concrete is different and it is ensured by friction and mechanical interlocking of the rebar surface. The chemical bond does not originate between GFRP reinforcement and the surrounding concrete, so adhesion does not contribute to transfer of the bond forces. Some few test methods are used to determine the bond between GFRP reinforcement and concrete. The pull-out test were used to determine the bond behaviour between GFRP rebars and concrete. This paper describes the preparation, process, results and evaluation of the pull-out tests.
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