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Sponsors: ACI Committee 549, Rilem-MCC Editors: Barzin Mobasher and Flávio de Andrade Silva Several state-of-the-art sessions on textile-reinforced concrete/fabric-reinforced cementitious matrix (TRC/FRCM) were organized by ACI Committee 549 in collaboration with RILEM TC MCC during the ACI Fall 2019 Convention in Cincinnati, OH, and the ACI Virtual Technical Presentations in June 2020. The forum provided a unique opportunity to collect information and present knowledge in the field of TRC and FRCM as sustainable construction materials. The term TRC is typically used for new construction applications whereas the term FRCM refers to the repair applications of existing concrete and masonry. Both methods use a textile mesh as reinforcement and a cementitious-based matrix component and, due to high tensile and flexural strength and ductility, can be used to support structural loads. The technical sessions aimed to promote the technology, and document and develop recommendations for testing, design, and analysis, as well as to showcase the key features of these ductile and strong cement composite systems. New methods for characterization of key parameters were presented, and the results were collected towards the development of technical and state-of-the-art papers. Textile types include polymer-based (low and high stiffness), glass, natural, basalt, carbon, steel, and hybrid, whereas the matrix can include cementitious, geopolymers, and lightweight matrix (aggregates). Additives such as short fibers, fillers, and nanomaterials were also considered. The sessions were attended by researchers, designers, students, and participants from the construction and fiber industries. The presence of people with different expertise and from different regions of the world provided a unique opportunity to share knowledge and promote collaborative efforts. The experience of an online technical forum was a success and may be used for future opportunities. The workshop technical sessions chairs sincerely thank the ACI staff for doing a wonderful job in organizing the virtual sessions and ACI TC 549 and Rilem TC MCC for the collaboration.

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.

The combination of short micro-fibers and continuous textile reinforcement in cementitious composites can yield desirable mechanical properties with respect to structural strengthening against severe loading, such as impact or blast. Besides the high tensile strength, high stiffness and considerable inelastic deformation capacity of such composites, their constitutive nature and fresh-state properties enable their application as thin layers by lamination or spraying without contributing substantially to the dead weight of the strengthened structure and without imposing the usage of molds and adhesives. The paper at hand presents an exemplary hybrid-fiber reinforced composite, consisting of high-strength strain-hardening cement-based composites (HS-SHCC) and carbon textile reinforcement. The textile was investigated in two configurations: with and without additional coating for bond-strength enhancement. In this way, the influence of yarn-SHCC bond properties on the cracking and fracture behavior of the composites was emphasized.

There is a great demand in the world for low-cost and functional pipeline systems due to the renovation requirements of pipes in use and the continuous development of new settlements. Previously used pipeline systems made of steel reinforced concrete are economical and sufficiently resistant. However, due to the corrodibility of steel reinforcement and to enable sufficient crack reduction, large wall thicknesses and thus heavy constructions are required. Textile reinforced concrete (TRC) eliminates these disadvantages by enabling the production of light and thin-walled structures.

The aim of this research is the development of a concept for the realization of smart pipes made of sensory TRC by using the advantages of lightweight, thin-walled structures, focusing on the production process. Based on different warp knitted textile variations with different coating concentrations, preliminary tests were carried out using the fourpoint bending test. As a result of the preliminary tests, the textile variation of counterlaid tricot with a maximum coating concentration was selected as a suitable reinforcing material for the concept development. Concepts for the production of smart TRC pipes are developed accordingly. As a result, a casting mold and process were created which allowed a production with reduced diameter and depth of pores and concentric positioning of the reinforcement structure.

Fabric Reinforced Cementitious Matrix (FRCM) is an established technology for strengthening and rehabilitation of existing concrete and masonry structures. In the United States, material characterization of the FRCM composites is in accordance with ICC-ES acceptance criteria AC434. The acceptance criteria recommend tensile testing the FRCM coupons with clevis-grips to obtain the mechanical properties for design purposes. The current test method, however, neglects some of the critical factors affecting the test outcome such as the effect of bonded length or number of fabric layers. The effect of bonded length on the FRCM properties tested per AC434 Annex-A is discussed in this paper. Carbon-FRCM coupons of 2, 3, 6, 9, and 12 inches (50.8, 76.2, 152.4, 228.6, and 304.8 mm) bonded length were prepared and tested in direct tension. The other test variable was the number of fabric layers. The tests were conducted with one- and two-layer fabrics for different bonded length. The results discussed in terms of ultimate stress, ultimate strain, and modulus show that the material characterization of the FRCM composites depended on the bonded length and number of fabric layers of the tested specimens. Moreover, the effect of number of fabric layers on the material characteristics was more pronounced in specimens with shorter bonded length. The experimental results are used to make suggestions for improving the FRCM characterization test methods as currently stated in AC434.