ACI 549.6R-20

This guide addresses the use of externally bonded (EB) fabric-reinforced cementitious matrix (FRCM) and steel-reinforced grout (SRG) systems for repair and strengthening of masonry structures. FRCM and SRG are composite materials composed of a reinforcement in the form of open fabric bonded on the masonry surface through an inorganic matrix. In particular, the structural reinforcement for FRCM consists of an open grid fabric of continuous fibers made of carbon, alkali-resistant (AR) glass, polyparaphenylene benzobisoxazole (PBO), aramid, or basalt fibers, while SRG systems use steel cords of twisted wires arranged to form a unidirectional fabric. The matrixes are typically based on combinations of portland cement, silica fume, and fly ash as the binder (cement-based), or on natural hydraulic lime (lime-based), or even on geopolymer (geopolymer-based). FRCM and SRG systems represent an alternative to traditional strengthening techniques such as steel tie rods, section enlargement, or even fiber-reinforced polymer (FRP) systems. FRCM and SRG systems can be used for various structural purposes—for example, they are used to:
1) increase the loadbearing capacity of structural members;
2) improve the seismic capacity of buildings;
3) counteract specific incipient or already developed damage;
4) limit opening of cracks; and
5) strengthen local weaknesses.

Based on experimental research, analytical work, and field applications, this guide provides the recommendations for the design and structural evaluation of FRCM and SRG systems according to both American and European existing regulations and guidelines.

Keywords: composites; confinement; earthquake-resistant; fabric-reinforced cementitious matrix; lap splices; mortar matrix; steel-reinforced grout; structural analysis; structural design.