Carbon Fabric Reinforced Cementitious Mortar confinement of concrete cylinders: the matrix effect for multi-ply wrapping

structures being able to improve both the axial strength and ductility. In the last decades, technological advances provided different tools/solutions for the achievement of an effective confinement, among all: the RC-jacket, the steel ties, the fibre reinforced polymer (FRP) wrapping, and lastly the fabric reinforced cementitious mortar (FRCM) plastering. The proposed research aims to investigate two open-issues and their combination related to the use of the FRCM, such as the multi-ply confinement and the role of the inorganic matrix with respect to the confinement effectiveness. At this scope, a set of pure compression tests were carried out to evaluate the representative laws of the mechanical behaviour of confined columns, namely the axial stress versus axial/lateral strain. Consequently, the axial strength and ductility gains were computed. In particular, the investigated variables were the grade of the inorganic matrix, by varying its compressive strength (i.e. ~25 MPa and ~50 MPa), and the number of plies (i.e. 1, 2 and 3). The results showed that the higher gain in term of axial strength and ductility is met by increasing the mortar’s compressive/tensile strength and, at the same time, the number of plies. Lastly, available design-oriented analytical models were found able to predict the FRCM-confinement effect in terms of strength. In addition, an available analysis-oriented model accurately foreseen the axial stress–strain law when dealing with the high-grade strength matrix confining in both single, double and triple layer of FRCM-system.