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.

Textile reinforced concrete (TRC) is a great composite material which offers many fields of application. It can be used as a material for the strengthening of existing concrete structures or to build new structures. Possible reinforcement materials are AR-glass, basalt or carbon. The last material named can be referred to as carbon reinforced concrete (CRC). The goal of the project autartec® was to create a floating house which is able to be self-sufficient for at least two weeks. For this purpose, structural elements made of CRC were developed. In this article, a case study of a specific staircase system will be presented. Besides the production of the elements, the paper will also discuss the experimental investigation of the system. On the one hand, the tests were carried out with the boundary conditions of regular use, on the other hand, unfavourable situations were considered. At the end, the complete staircase system will be demonstrated.

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.

The increasing interest in the field of conservation of existing masonry structures pushed to the development of new retrofitting technologies in the recent past. One of the most promising is the use of Fabric Reinforced Cementitious Mortar (FRCM), which consists of an open-grid within an inorganic matrix. The effectiveness of the FRCM-application is well-demonstrated in literature by several experimental investigations regarding different structural members, including columns and shear wall. The success of FRCMs is manly related to durability aspects, since the grid is generally non-metallic, the compatibility of the inorganic matrix with the substrates, the easy application, the low weight and spatial impact, the possible installation in damp areas and at high temperatures. The interaction between the substrate, the mortar-based matrix and the open-grid make challenging the theoretical prediction of the mechanical behavior of the FRCM-retrofitted structures. For this reason, the analytical formulations for the proper design of FRCM-strengthening are still an open research problem, referring to both short and long term conditions. The present paper reports and discusses design-oriented relationships for FRCM-confinement and in-plane FRCM-strengthening of masonry elements; the proposals are intended to satisfy the requirements of simplicity and accuracy needed for code-finality.

The influence of engineered hydrophilic polypropylene fibers in the formation of distributed cracking and the associated strengthening and toughening of cement-based composites under mechanical loading was studied by conducting, correlating, and modeling tensile and flexural tests. An automated filament winding system was used to manufacture continuous fiber composites. Composites with continuous fibers consisting of low modulus surface-modified hydrophilic macro-synthetic polypropylene fibers were compared for their reinforcing ability with fibrillated micro-synthetic fibers. The digital image correlation technique was used for damage characterization using quantitative analysis of crack width, spacing, and correlated with the tensile response and stiffness degradation. It was observed that the mechanical properties as well as crack-spacing and composite stiffness were significantly affected by the microstructure and dosage of continuous fibers. Procedures for correlating tension and flexural test results were introduced using closed-form solution approaches for strain hardening materials.