scope:

Preface

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 motar 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 terminology adopted in ACI to identify this class of new products is FRCM (fabric reinforced cementitious matrix) when the reinforcement is made of man-made fibers and SRG (steel reinforced grout) when the reinforcement is made of ultra-high strength steel. While it is recognized the other organizations and professionals may refer to these systems with different acronyms and names (for example, TRM for textile-reinforced mortar, TRC for textile reinforced concrete), ACI Committee 549 has made the conscious decision to adopt FRCM and SRG to unequivocally identify systems solely intended for repair and strengthening as opposed to new construction.

The two technical sessions and the resulting Special Publication were also the first tangible outcomes of the partnership between ACI Committee 549 and Rilem TC 250 that has as its ultimate objective, jointly producing a design guide for the repair/strengthening of masonry structures using FRCM and SRG, The motivation of the partnership stems first from the desire to maximize efficiency by drawing from the experience and expertise of professionals from aroud the world. Additionally, the intention is to develop a guide that harmonizes the design procedure based on the approaches followed in the U.S. and European Union so that practitioners can adopt this technology irrespective of the geographical location and with the same outcome.

The editors of this SP are most grateful to the technical sessions presenters and the authors of the papers for having shared their precious knowledge. The editors hope that this SP will be a relevant contribution to the deployment of suitable technologies for the safe preservation and use of existing concrete and masonry structures.