It is believed that the use of mortars based on air lime in the construction and renovation of brick buildings has a number of advantages, especially those closely related to the durability and strength of the structure. However, there is still a noticeable difference in the mechanical properties of these materials. This research investigated the mechanical characteristics of a mixed cement–lime mortar with the two most popular proportions of an air lime, cement, and sand mix: 1:1:6 and 1:2:9 (by volume). Mechanical tests were performed on standard and non-standard samples to assess compressive strength, tensile strength, flexural strength, and fracture energy. The obtained results indicate the possibility of using these mixtures in modern masonry construction, as well as in the aspect of sustainable development. Additionally, lime mortar with a higher lime content can be used in non-load-bearing walls and in renovation and repair works.

The basic issue in determining the deformational properties of masonry is to conduct a comprehensive experimental characterization of the masonry components' materials, including their mechanical properties. This characterization process is even more important for new sustainable mortar solutions, especially in the context of strengthening and renovating existing masonry buildings, including historic structures. The work presents and discusses the mechanical tests carried out on a mixed cement-lime mortar based on air lime and reinforced with the addition of industrial glass fibres. Mechanical testing on prisms (40 × 40 × 160 mm) and cylinders (60 diameter × 120 mm height) demonstrated the beneficial impact of fibres in the mortar mixture analysed specifically in terms of improved compressive, flexural and splitting post-peak behaviour.