Performance assessment of different consolidation techniques for multi-leaf stone masonry walls

In the paper, the performances of different repair techniques applied on three-leaf stone masonry walls are analyzed. In particular, the following interventions have been considered: (i) injections, to consolidate the weak internal layer; (ii) repointing of the mortar joints, to counteract the deterioration of mortar in the external leaves; (iii) transverse tying through the thickness of the wall, to provide a connection among the different whytes and, finally, (iv) all the possible combinations of the above mentioned techniques, in order to improve the effects of the single interventions and optimize the execution modalities. The comparison between the mechanical behaviour of stone masonry walls, before and after the consolidation, has been pointed out by a series of laboratory tests on real size wall specimens. The masonry samples have been subjected to compressive loads tests before and after repair, in order to detect the mechanical behaviour of the walls in terms of strength, stiffness and deformability parameters. Moreover, an extensive sonic tests campaign, performed by direct and indirect tests and tomography elaborations, allowed estimating the effectiveness of the proposed techniques. A remarkable efficiency of the NDT in detecting the variations in the walls consistency, together with a good agreement of the NDT results with the outcomes of the interventions survey and of the mechanical tests, have been noticed.