Experimental and numerical study on retrofitting of historical masonry vaults by means of fibre-reinforced mortar

Arches and vaults represent important components in historical masonry structures. From the mechanical point of view, they represent the only way to create large openings or horizontal floors without resorting to tension-resisting elements. However, past research and observations of damage after seismic events have highlighted the high vulnerability of such elements under horizontal actions. Moreover, in monuments and historical heritage their intrinsic artistic value is often significant, and thus the need for repairing or retrofitting must compromise with the requirements of compatibility with the old materials present. In this context, the use of lime-based mortar as re-pointing or surface treatment would represent the optimal material, but its low tensile strength and high brittleness make it unsuitable as a retrofitting technique. The introduction of natural or artificial fibres in the mortar paste may remarkably increase the strength and the ductility of the material, making it competitive to other techniques and preferable from the viewpoint of compatibility. In this research, a retrofitting technology based on the application of fibre-reinforced lime-based mortar (FRLBM) on masonry vaults is investigated. Scaled 1.5m-span arches made of tuff blocks, which represent the most common block material in Southern Italy, are experimentally tested under constant vertical loads and monotonic horizontal forces. The arches are tested in unreinforced and reinforced configuration, consisting of 1-cm thick layer of mortar applied at extrados. The results show a remarkable increment in strength and ductility of the arches as an effect of the FRLBM. Numerical simulations of the retrofitting technique are also developed and allow for the extension of the experimental results to different configurations. Future improvements of the technique and the materials are envisaged based on the outcomes of the described activities