Historic masonries of the cultural heritage are aged and heterogeneous systems which are subjected to long-term exposition to the external environment. In such conditions, they can easily come in to contact with a consistent range of damaging agents, including water and salts sources. The related salt-induced damage is widely considered as one of the most dangerous decay process for their preservation. Conservative operations become therefore necessary and are performed with new materials that must fulfil specific requirements regarding their compatibility with the original ones and their resistance to damaging agents, especially in term of salt-resistance. The use of ready-mixed mortars in the restoration field has become a common practice and the number of commercial products currently available in the market is increasing. The present work reports the investigation on four types of ready-mixed mortars based on NHL binders and on two commercial NHL binders, together with the preliminary laboratory tests to assess the durability of mortar specimens to salt decay. The investigation provided useful information on the relationship between compositional and microstructural features and damage.