Organic versus inorganic matrix composites for bond-critical strengthening applications of RC structures – State-of-the-art review

Abstract

The usage of organic matrix composites such as fiber reinforced polymers (FRP) in retrofitting of structures is increasingly becoming popular among structural designers, which is credited to varied attractive top features of these materials, such as: corrosion resistance, higher strength to weight ratio, ease and speed of application, and almost no section enlargement. However, FRP strengthening technique is not completely free of problems. The organic resins employed as binders have many disadvantages such as (a) relatively expensive resins; (b) poor response at temperature ranges above the glass transition temperature; (c) potential risks for the workers; (d) difficulty in application on moist areas or at low temperature ranges; (e) difficulty of reversibility (inability to undo the repair without damaging the original structural member); and (f) non-compatibility between resins and substrates. One possible solution for alleviating these difficulties is the substitution of the organic with the inorganic binder, such as cementitious mortars. A new class of material was then developed and used for structural strengthening applications. In this material, fibers are replaced by textile or fabric and organic matrix is replaced by cementitious matrix such as mortars and is usually called textile reinforced mortar (TRM). This paper presents a critical review of existing research on comparison between FRP and TRM composites used for strengthening of structural concrete members, identifies gaps in current knowledge, and outlines directions for future research. It briefly presents material characterization in terms of constituents and stress-strain behavior in tension, and also describes concisely methods of installation for both organic and inorganic composite systems. Available literature on bond behavior at composites-to-concrete interface at ambient and elevated temperatures are summarized. It also enlists available research on use of TRM composites in comparison with FRP composites for flexural and shear strengthening of RC beams.