Compressive Behavior of Masonry Columns Confined with FRCM Systems: Research Overview and Analytical Proposals

Fabric–reinforced cementitious matrix (FRCM) composites have emerged as a viable solution for the external confinement of deficient masonry members. They represent an appealing alternative to fiber–reinforced polymer (FRP) systems since the use of epoxy matrixes raises some unsolved issues, such as the poor composite–substrate compatibility, low permeability of the strengthened surface, and the difficulties in removing the FRP sheets without damaging the substrate. To investigate the efficacy of FRCM confinement, a number of experimental investigations have been published in the literature, and a wide overview will be reported in this paper. However, to date there is a lack of relevant analytical studies that propose sound models to estimate the compressive strength of FRCM confined masonry; difficulties are related to the high complexity and heterogeneity of the masonry and to the uncertainties that are derived from FRCM confinement, whose performance is affected by many variables, which include the quality of the inorganic matrix and geometry of the fabric mesh. Most of the collected studies focus on investigating the applicability of the existing formulations that are suitable for FRP systems to examples of FRCMs, a few others provide promising proposals although they were validated using a limited amount of experimental data. This paper will present an analytical study on the confinement of masonry columns with FRCM composites with two aims: (a) propose new models to estimate the compressive strength; and (b) assess the existing formulas. A wide database that includes the results of compression tests on 211 masonry members that are externally wrapped with FRCM systems will be assembled from the literature. The collected data will be organized into a systematic framework and will be analyzed based on some relevant parameters, such as the type of fiber [e.g., basalt (B), carbon (C), glass (G), steel (S), and poliparafenilenbenzobisoxazole (PBO)], the geometry of the mesh, number of layers employed, mechanical properties of the inorganic matrix, and compressive strength of the unconfined masonry (fmc). Strength models for FRCM confined masonry will be developed by best-fit analyses, and comparisons with formulations that are available in the literature and some international guidelines will be performed.