Durability of FRP-confined concrete

In the last decade fibre-reinforced polymer (FRP) composites have been successfully used for confinement of reinforced concrete (RC) and masonry columns. Their high mechanical properties, light weight and low installation costs have contributed to making the wet lay-up wrapping one of the most affordable techniques for column confinement. Although previous studies have demonstrated the high performance of FRP strengthening systems, there are several concerns related to the long-term behaviour of wrapped columns which have limited full implementation. It is well known that after cracking of the concrete core, the development of an elastic pressure produced by the FRP jacket increases the strength and ductility of the unconfined column. Nevertheless, environmental effects, such as freeze-thaw cycles, wet-dry cycles, ultraviolet radiation exposure and de-icing salt solutions may affect the material properties, and therefore the structural response of the wrapped elements. In this study an experimental investigation was performed in order to study the long-term behaviour of FRP-confined columns. Glass and carbon FRP systems were used to wrap small-scale concrete cylinders that were subjected to environmental cycles and immersion in aggressive aqueous solutions. Durability effects, due to environmental cycles or immersion in solutions, were found to affect the mechanical properties of FRP-confined concrete.