| Resumo: | Grout injection is a widely used technique for masonry consolidation of multi-leaf 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, with or without special admixtures (such as superplasticizer). To ensure an adequate flow of the grout and a correct filling of the internal voids inside the masonry, it is essential to assure good fresh grout properties. The evaluation of the performance of the grout injectability is firstly started by checking the intrinsic properties of the grout (namely fluidity, stability, water retention and rheological parameters) and then by controlling the injectability through injection tests. Besides the grout composition, the environmental temperature, resting times and injection pressure also play a significant role on the grout injectability. The lack of information about the influence of the referred parameters on the injectability of hydraulic lime grouts enhances the importance of a detailed research on the subject. The grout specification involves the knowledge of the flow capacity within the masonry inner core and physic-chemical compatibility with the original materials present in the old masonries. Thereby, it is evaluated the injection performance of hydraulic lime based grouts as a function of the porous media to be injected. For this purpose, simplified models were created to allow injectability tests in controlled conditions. To enable the simulation of different permeabilities and internal structures of masonries, the models were created by filling plexiglass cylinders with different grain size distributions of limestone sands and crushed bricks. As these materials exhibit different water absorption coefficients, it also was possible to study the influence of water loss from grout to porous media in grout injectability. Another variable studied with influence on grout injectability was the water content of porous media. As it is not expected that masonries are always dried, the pre-wetting of some cylinders by simple injection of water is of extreme relevance to compare the results of grout injectability in the two opposite situations. The injection tests also enabled to detect different resistances to grout penetration created by the PM to the flow. The knowledge of these resistances is crucial to estimate the grout penetration in the internal voids. The grout injection performance was analysed both in the fresh and hardened states. In order to test the effectiveness of the filling process and the bonding of the grout to the masonry materials, tomography was conducted complemented with mechanical tests. The mechanical results showed good correlation with injectability and dependence with the position of the specimen analysed on the cylinder injected, creating tensile and shear strength gradients along the height of the cylinder. In what concerns the tomography, the research demonstrated a correspondence between the characteristics of the cylinders after the injection and the information displayed in the tomograms. Thus, it is proved that tomography is a useful technique to evaluate effectiveness of the grout injections, allowing an understanding of the ability of the injections to modify the physical and mechanical properties of old masonries.
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