Fabric-Reinforced Cementitious Matrix (FRCM) Carbon Yarns with Different Surface Treatments Embedded in a Cementitious Mortar: Mechanical and Durability Studies

Abstract

Nowadays, FRCM systems are increasingly used for the strengthening and retrofitting of existing masonry and reinforced concrete structures. Their effectiveness strongly depends on the bond that develops at the interface between multifilament yarns, which constitute the reinforcing fabric, and the inorganic matrix. It is well known that fabric yarns, especially when constituted by dry carbon fibers, have poor chemical-physical compatibility with inorganic matrices. For this reason, many efforts are being concentrated on trying to improve the interface compatibility by using different surface treatments on multifilament yarns. In this paper, three different surface treatments have been considered. The first two involve yarn pre-impregnation with flexible epoxy resin or nano-silica coating, while the third one involves a fiber oxidation process. Uniaxial tensile tests were carried out on single carbon yarns to evaluate tensile strength, elastic modulus and ultimate strain before and after surface treatments, and also after yarn exposure to accelerated artificial aging conditions (1000 h in saline or alkaline solutions at 40 °C), to evaluate their long-term behavior in aggressive environments. Pull-out tests on single carbon yarns embedded in a cementitious mortar were also carried out, under normal environmental conditions and after artificial exposure. Epoxy proved to be the most effective treatment, by increasing the yarn tensile strength of 34% and the pull-out load of 138%, followed by nano-silica (+9%; +40%). All surface treatments were shown to remain effective even after artificial environmental exposures, with a maximum reduction of yarn tensile strength of about 13%.

New Materials and Technologies for Durability and Conservation of Building Heritage

“…Several studies have focused on the mechanical characterization of FRCM [ 100 ], on the bond at the interface between the internal reinforcement and the inorganic matrix [ 101 , 102 , 103 ] and on the effectiveness of different FRCM systems to repair and strengthen masonry or concrete elements [ 104 , 105 , 106 , 107 , 108 ]. There are still other issues to be further investigated, such as the long-term behavior and durability of FRCM systems when exposed to aggressive environments [ 109 , 110 , 111 , 112 , 113 ], high temperature or fire scenarios [ 114 , 115 ].…”

Bond strength of substrate with repair material for masonry structures

“…Researchers are inculcating the use of different composites to strengthen old structures; few authors proposed the use of a fibre-reinforced matrix to enhance the mechanical properties of the structures. Most studies include testing tensile strength and conducting the shear test to understand failure behaviour [10][11][12].…”

“…Complex Nature of Ancient Mortar: There are significant disparities in the constituents of ancient mortar [10,11]. Ancient masonry is intricate, mostly unreinforced or with traditional reinforcement, and often integrated into complex structures.…”

Functional Coatings and Surface Modifications in Cement–Matrix Composites

“…The latest findings on the functionalization of reinforcing fibers and rebars in concrete involve the use of nano-coatings. Nano-silica coating was implemented by Bompadre and Donnini [30] to increase the tensile strength and the pull-out load of carbon fiber incorporated in textile-reinforced mortars. Nano-CaCO 3 coating was used by Yong et al [31] to treat PVA fibers, aiming at enhancing the interfacial bonding properties of fiber-reinforced concrete.…”