Abstract
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.
Highlights
The possibility of reinforcing concrete elements by externally applying fiber reinforced polymer (FRP) systems has become a well-established solution within the construction industry
After the failure of the inner concrete the specimen maintains a high stiffness, due to the presence of the Fiber Reinforced Cementitious Matrix (FRCM) inorganic matrix, and the slope of the curve is higher if compared to FRP wrapped specimens
FRCM systems increased the compressive strength of the concrete columns of 1.2 up to 1.6 times the initial strength
Summary
The possibility of reinforcing concrete elements by externally applying fiber reinforced polymer (FRP) systems has become a well-established solution within the construction industry. The effectiveness of these systems has been validated by several experimental investigations [1,2,3,4]. FRCM systems proved to be very effective as external reinforcement for masonry or concrete elements, even though the adherence developed at the interface between fabric and mortar is not as high as in the case of organic based systems (FRPs). The use of High Performance Mortar (HPM) jackets is another of the emerging possibilities to reinforce existing concrete elements. The use of Calcium Oxide showed to further improve the mortar mechanical properties [16]
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