Grout injection effect on the shear behavior of FRCM strengthened stone masonry panels

During the last decades, several seismic phenomena have shown the high vulnerability of existing stone masonry structures subject to horizontal actions. Innovative composite materials, such as Fiber Reinforced Cementitious Matrix (FRCM), can be adopted for the retrofitting of masonry structures. The use of these innovative FRCM systems is usually combined with a more traditional retrofitting technique: grout injection. It allows to restore or improve the transversal connection between wall leaves, ensuring a monolithic behavior of the structural element. The objective of this research was to analyze the effect of the quality of the grout injection on the shear response of FRCM strengthened stone masonry panels. Results from an experimental campaign, where stone masonry specimens were subject to diagonal compression tests, are therefore presented in this paper. Two samples were subject to grout injection and one of them was strengthened with Steel Reinforced Grout (SRG). Comparisons between the experimental results showed that grout injection alone, if correctly executed, could determine a significant improvement in the shear capacity of masonry panels. The application of the FRCM strengthening system could further enhance the behavior of the samples, especially influencing the failure mode. Comparisons with analytical formulations for the evaluation of the capacity of strengthened walls are also presented.