Fabric-reinforced cementitious matrix (FRCM) is a new class of composite materials that raised great interest in the last years as a promising technique to upgrade, strengthen and rehabilitate concrete or masonry structures. FRCM systems are constituted by a structural reinforcement fabric, consisting of an open grid of perpendicularly connected multifilament yarns (usually made of carbon, glass, or basalt fibers), applied on concrete or masonry structural elements through a cement- or lime-based matrix. In this study, the effects of using different surface treatments on dry carbon yarns have been evaluated, both considering mechanical performances and durability. Three different surface treatments have been investigated, the first two consisting of yarns pre-impregnation with epoxy resin or nano-silica coating while the third one is a process of fibers oxidation. Tensile tests on carbon yarns and pull-out tests have been carried out to evaluate the effects of the treatments both under normal environmental conditions and after artificial exposure in saline and alkaline environments.

Externally bonded (EB) steel reinforced grout (SRG) composites have the potential to improve the flexural and shear performance of existing concrete and masonry structural members. However, one of the most commonly observed failure modes of SRG-strengthened structures is due to composite debonding, which reduces composite action and limits the SRG contribution to the member load-carrying capacity. This study investigated an endanchorage system for SRG strips bonded to a concrete substrate. The end anchorage was achieved by embedding the ends of the steel cords into the substrate. Nineteen single-lap direct shear specimens with varying composite bonded lengths and anchor binder materials were tested to study the effectiveness of the end-anchorage on the bond performance. For specimens with relatively long bonded length, the end-anchorage slightly improved the performance in terms of peak load achieved before detachment of the bonded region. Anchored specimens with long bonded length showed notable post-detachment behavior. Anchored specimens with epoxy resin achieved load levels significantly higher than the peak load before composite detachment occurred. For specimens with relatively short bonded length, the end-anchorage provided a notable increase in peak load and global slip at composite detachment. A generic load response was proposed for SRG-concrete joints with end anchors.

Textile-reinforced concrete (TRC) is a composite material resulting from the combination of finegrained concrete and textile reinforcement, widely used to strengthen existing structures. In addition, TRC is an alternative to obtain lighter and thinner structures. However, the behavior of these structures depends on the properties of the matrix and fiber used, as well as on the interface between these two phases. In this work, the interface properties of SBR-based carbon textile-reinforced concrete as supplied and after sand-coating treatment are evaluated through pullout tests. Then, to assess the bending behavior of structural members, four-point bending tests were performed on I-section beams using textiles with and without surface treatment. To analyse the evolution of cracking, digital image correlation (DIC) technique was used. The effectiveness of epoxy-sand treatment surface in textile reinforcement improve the bond between textile as well matrix as the failure mode of TRC beams and was confirmed by improved interface properties, i.e. a stiffer and stronger interface was obtained. In addition to the improved crack pattern, it was observed smaller and less spaced cracks.

A reinforced concrete bridge built in 1940 and located in Dallas, Texas, exhibited moderate to severe corrosion-related deterioration in the concrete bent caps. The damaged bent caps were repaired with epoxy mortar and externally strengthened with carbon fiber reinforced polymer (CFRP) laminates. Three-dimensional numerical models of the bent caps were created to better understand the cap behavior in bending and during various stages of the repair. The models were calibrated using data obtained from full-scale live load bridge testing. . The models were loaded until failure (rapid crack opening or CFRP debonding) to show the crack patterns, strain distributions and the bent cap capacities. The bent cap moment capacity increased by about 30% after repair/strengthening, because the original bent caps had extensive damage at the flexure-critical areas. The dowel-connected newer bent caps from the 1970 widened bridge contributed to the load sharing with the older bent caps.

Recently the use of special reinforcement arrangements has been extended in reinforced concrete members under torsion. These arrangements include (a) continuous rectangular spiral reinforcement, (b) epoxy bonded Carbon Fiber Reinforced Polymer (C-FRP) sheets as external transverse reinforcement and (c) short steel fibers as mass reinforcement. In this study an extended experimental program of 14 beams tested under torsion is presented. All specimens have the same geometrical characteristics but different transverse reinforcement arrangements. Six beams are used as pilot specimens; three of them have no transverse reinforcement and three have conventional steel stirrups. Further, two specimens have continuous steel spirals; four specimens have steel fibers as mass reinforcement and two specimens have externally bonded C-FRP sheets. The torsional behavior of these specimens is presented and compared to the behavior of the pilot specimens. Discussion and explanatory design examples about the application of these reinforcements are also included.