Injection capacity of hydraulic lime grouts in different porous media

Grout injection is a widely used technique for consolidation of multi-leaves masonries, aimed at increasing the compactness and to create links between the internal and external leaves that will improve shear, flexural and compressive resistances. Grouts can be seen as mixtures of binder with water, admixtures and/or additives, which should present low viscosity and high penetrability. The definition of a grout composition should involve the knowledge of the injection capacity within a specific type of masonry and good physical and chemical compatibility with the original materials present in the historic structures. The flow of the grout through the masonry depends on the fresh grout properties, such as stability, water retention and rheological behaviour. Thus, the evaluation of the performance of the grout as function of a porous medium is firstly started by checking the intrinsic properties of the grout (namely rheological and stability) and then by controlling the injectability of masonry by injection tests on cylinders. Since it is difficult to reproduce a real masonry and to visualize what is happening inside the porous medium being injected, masonry samples were created by filling plexiglass cylinders with a fraction of limestone sands and crushed brick. These materials are sieved to obtain different grain size distributions to enable the simulation of different permeabilities and internal structures for the masonry. The lack of information about the performance of hydraulic lime based grouts as a function of the properties of the porous medium to be injected enhances the need of a detailed research on the subject.