Concrete columns confined with different composite materials

In the last decades, the need for upgrading, strengthening and retrofitting of existing concrete structures is rapidly growing. Composite materials showed to be an optimal solution to face this problem, combining high efficacy with low invasiveness. The use of Fiber Reinforced Polymers (FRP) to wrap concrete columns has been widely investigated and became a very successful method to improve their structural performances. However, it has been recognized that FRPs, due to the presence of an organic resin, have a few drawbacks, such as poor mechanical behavior at high temperatures, lack of vapor permeability and impossibility to be installed on wet surfaces. This experimental work aims to propose a comparison between three different innovative methods as possible strengthening solutions for existing concrete columns. The structural behavior of 20 reduced scale concrete columns, realized by using a low performance concrete, in order to reproduce the poor mechanical properties of existing structures, was investigated. Two unreinforced column were tested in compression as reference. Six of them where reinforced by applying an external layer of FRP, with different types of fabric reinforcement (made of carbon or PBO fibers). Six columns were reinforced by using the same fabrics coupled with an inorganic matrix (FRCM) instead of epoxy. Six other columns were reinforced by using a layer of High Performance Fiber Reinforced Concrete (HPFRC) of 3 cm thick. Experimental results have been analyzed and performance of the three reinforcement systems have been compared.