Advances and open issues in the use of fiber-reinforced composites as reinforcement of existing and new constructions

Fiber-reinforced composites have been increasingly used in the last decades to reinforce existing and new structures. Among them, fiber-reinforced polymer (FRP) composites have been adopted as externally applied reinforcement of existing concrete, masonry, steel, and timber structural members to increase their bending, shear, and axial capacity. FRPs have been used also as internal reinforcement of concrete structures in applications where their peculiar physical and mechanical properties make them a valid alternative to traditional steel reinforcing bars. Fiber-reinforced cementitious matrix (FRCM), also referred to as textile-reinforced mortar (TRM) and textile-reinforced concrete (TRC), composites have been proposed to overcome some of the issues related to the use of organic resins in FRPs, such as the absence of vapor permeability and poor resistance to (relatively) high temperatures. In addition, inorganic mortar plasters reinforced with FRP grids have been used in composite reinforced mortar (CRM) systems applied to masonry structures. The growing use of fiber-reinforced composites in construction has boosted research in this field, improving the state of knowledge and promoting the safe and reliable application of these innovative technologies. Nevertheless, open issues still remain, and ongoing and future research is essential to fully exploit the possibilities offered by fiber-reinforced composites in the world of construction. This paper explores the key features of fiber-reinforced composites, outlining their advantages over traditional materials and shedding light on the challenges that still need to be addressed. Emphasis is placed on the contributions provided by the author at the Politecnico di Milano over the past 15 years.