Abstract This study gives an example of the steps that a repair work must include to be successful. It deals with a specific building, repair material (lime mortar) and application (render), but also with the study of the repair mortar in the laboratory and on site. Firstly, the original materials of the wall were characterized to ensure compatibility with the new repair mortars. Secondly, the suitability of different mortar mixes, made with lime and calcareous aggregate, was assessed by characterizing their properties after 15 months. At the same time, the repair mortars were applied in testing panels, and their behaviour under environmental conditions was studied and compared with that of the laboratory mortars. Mortar properties (shrinkage, adhesion, mineralogy, microstructure and texture) developed differently according to the curing conditions. The carbonation degree was higher in mortars cured on site (especially those with higher aggregate content), although in both cases it depended on mortar porosity. Testing the type of application on site was helpful to define the best performance of the designed mixes and to choose the most suitable one among them, which was found to be the 1:6 binder-to-sand ratio mortar applied in both layers of the render.

Abstract This work highlights the importance of applying suitable methods for the design of air-hardening lime mortars with the correct water dosage and binder-to-aggregate ratios. To this end, the recently developed ‘wet packing method’ has been used to assess the optimum water-to-binder ratio at which the packing density is achieved in lime mortars with different binder-to-aggregate proportions. To support the validity of this method, it has been compared with other standardized methods of determining the bulk density of the dry granular components and the consistency of the mortar pastes. The reliability of the wet packing method has then been verified by studying the mineralogical, textural and mechanical properties of mortars after 2 and 6 months of carbonation. Results showed that although the wet packing method seems to be more realistic than the majority of standards used for the determination of the packing density and workability in granular mixtures, it is not totally suitable for the preparation of air-hardening lime mortars with good performances in the fresh and hardened state.