This SP is the result of two technical sessions held during the 2017 ACI Spring Convention in Detroit, MI. Via presentations and the resulting collection of papers, it was the intention of the sponsoring committees (ACI Committees 549 and 562 together with Rilem TC 250) to bring to the attention of the technical community the progress being made on a new class of repair/strengthening materials for concrete and masonry structures. These materials are characterized by a cementitious matrix made of hydraulic or lime-based binders, which embeds reinforcement in the form of one or more fabrics also known as textiles. The great variability of fabric architectures (for example, cross sectional area, strand spacing, and fiber impregnation with organic resin) coupled with the types of material used (aramid, basalt, carbon, glass, polyparaphenylene benzobisoxazole (PBO) and coated ultra-high strength steel) makes the characterization, validation, and design of these systems rather challenging. Irrespective of the reinforcement type (synthetic or ultra-high strength steel), the impregnating mortar is applied by trowel or spray-up. It should also be noted that fabric reinforced cementitious matrix and steel reinforced grout, in particular, are very different from other repair technologies such as FRC (fiber reinforced concrete) and UHPC (Ultra High-Performance Concrete) in that they utilize continuous and oriented reinforcement. In a sense FRCM and SRG can be viewed as the modern evolution of ferrocement.

The use of Fiber Reinforced Polymer (FRP) strengthening systems for reinforced concrete (RC) members represents nowadays an effective alternative to traditional strengthening techniques. Recently, a new class of composites have emerged known as Steel Reinforced Grout (SRG), consisting of steel fibers embedded in an inorganic matrix and applied by using manual techniques and traditional handcraft. An experimental campaign was recently carried out that aims at assessing the performance and effectiveness of SRG strengthening systems to improve the flexural behavior of RC slabs. The present work uses the experimental results to validate the numerical prediction of a FEM code, developed by the authors, to analyze the flexural behavior of SRG-strengthened slabs. The cross-sectional response is obtained using a fiber-model equipped with a plasticity model for rebars, a continuumdamage model for SRG, and a plastic-damage model for concrete. Overall, the numerical predictions are in good agreement with the experimental results. The model reproduces with acceptable accuracy the nonlinear behavior of the tested strengthened beams, as well as the failure point both in terms of failure modes and ultimate strength and displacement. In some cases, slight differences can be found between the numerical and experimental results. These differences are discussed in this work.

In the last decade, Fibre Reinforced Cementitious Matrix (FRCMs) became an interesting inorganic alternative to the widespread organic-based Fibre Reinforced Polymers (FRPs). FRCMs are more appealing as retrofitting materials for masonry structures thanks to their generally better compatibility to existing masonry substrates, especially when lime-based matrices are used. In this framework, two FRCMs were tested to evaluate their tensile and shear bond mechanical behaviours, when applied to brick masonry prisms. One FRCM was made of a hydraulic lime mortar coupled with an alkali-resistant glass fibre mesh, while the other was made of a latex-modified cement mortar coupled with a carbon mesh. Tensile tests and single lap shear tests were performed to characterize the relevant strengths of the two FRCMs. The objective was the definition of the basic design parameters for the appraisal of the two FRCMs as strengthening inorganic composite materials for masonry structures. In this paper, the experimental results will be presented and discussed with the definition of the tensile and bond design strengths of the two FRCMs. An example of application with related normalized cost estimations is also provided; it showed that the best trade-off of mechanical performance and cost-effectiveness was given by the carbon mesh FRCM.

Fiber-Reinforced Cementitious Matrix (FRCM) composites are becoming a widespread technology for the rehabilitation and strengthening of historic masonry and reinforced concrete structures due to some advantages that allow them to be a suitable alternative to Fabric-Reinforced Polymer (FRP) composites. In this work, a new family of FRCM composites system made of ultra-high strength steel cords installed with either hydraulic lime or cement based mortars named Steel Reinforced Grout (SRG) is presented. This paper briefly introduces to the main properties and mechanical characteristics of SRGs, and introduces case studies on masonry and reinforced concrete structures demonstrating the different field applications of this new and effective strengthening solution.

This paper presents the results of an experimental program carried out to study the behavior of brick masonry columns confined by steel reinforced grout (SRG) comprised of continuous steel fiber cords embedded in a cementitious matrix. Short brick masonry columns with a square cross-section confined by SRG jackets were subjected to a monotonic concentric compressive load. Parameters investigated in this study were the area weight of steel fibers and the masonry column corner radius. Results show that the SRG jackets increased the compressive strength of the masonry columns by 26-42% relative to the unconfined masonry columns. The compressive strength of the confined columns increased slightly with increasing corner radius ratio and with increasing fiber area weight.