Effectiveness of injections evaluated by sonic tests on reduced scale multi-leaf masonry building subjected to seismic actions

The results of the application of NDT on two reduced-scale (2:3) buildings subjected to shaking table tests at the laboratory of ENEA (Rome) are presented. The models have two storeys and are made of three leaves stone masonry and timber floors, connected to the walls by steel ties. One model was strengthened by injections before test, in order to compare the effectiveness of the intervention in increasing its strength. The models reproduce the typical pattern of buildings in historical centres, where the use of poor materials (especially mortar) and the lack of strong connections among them, is responsible of their high seismic vulnerability. To pursue preservation criteria, compatible grouts were proposed, based on natural lime-mortar binders. A preliminary phase of materials characterization was performed (on stones, mortar and grouts), and non-destructive investigation methods were also applied. Particularly sonic waves, before and after injection, applied as direct and tomographyc tests, allowed identifying the grout penetration pattern and validating the intervention.