Grout requirements for the injection of stone masonry walls

In the paper, an experimental procedure for the choice of injection grouts, aimed to the optimization of stone walls injectability, is presented. To minimize compatibility problems between the original walls and the grouts, natural hydraulic-lime grouts have been used. The selection of the suitable grout is firstly performed by checking the intrinsic rheological properties of grouts (fluidity and stability) and then by controlling the injectability of masonry (penetration and diffusion of grouts) by injection tests on cylinders. Different particle-size distributions simulating the infill of multi-leaf stone masonry walls have been considered, as well as the influence on the injectability of different additives. The selected grouts have been consequently used for the consolidation of real-scale physical models of three-leaf stone masonry walls. The experimental results obtained from mechanical tests carried out both on materials (grouts), cylinders and wall samples, allowed to calibrate an analytical model able to predict the compressive strength of injected multi-leaf stone masonry walls. It is based on simple laboratory tests on the materials and on in situ survey and MDT applications on the masonry. Such approach, besides allowing the better exploitation of the grouts performances, can provide a practical contribution for the design of the repair intervention, aimed to the achievement of the maximum effectiveness.