Use of Composite Reinforced Mortar (CRM) Systems to Strengthen Existing Masonry Structures

Composite reinforced mortar (CRM) systems have been increasingly adopted to strengthen existing masonry members in the last decade due to their interesting features. They are usually cheaper than fiber-reinforced cementitious matrix (FRCM) composites and can be easily and quickly installed. CRM systems comprise a composite grid, usually made with glass fiber-reinforced polymer (GFRP) composite, embedded within an inorganic mortar. The grid can be fixed to the substrate using different types of anchorages, while the mortar can be applied by hand or even sprayed over the grid. CRM overlays were shown to be effective in increasing the in-plane and out-of-plane strength of masonry walls, as well as to realize crowning beams aimed at improving the behavior of the masonry structure. However, CRM systems are still a recent solution, limited experimental results can be found in the literature, and no design guidelines are available. In this paper, a state of the art on the use of CRM systems to strengthen masonry walls is provided. The available literature is analyzed. Experimental results on CRM-strengthened masonry walls subjected to in-plane and out-of-plane loads and of crowning beams subjected to bending tests are discussed. This paper provides an insight into the effectiveness of CRM systems, their main features, and open issues that hinder their diffusion.