Confinement of Masonry Columns with Natural Lime-Based Mortar Composite: An Experimental Investigation

The paper presents the results of an experimental campaign on the confinement of masonry square columns with fiber-reinforced lime mortar (FRLM) composites made of a natural lime-based matrix. The experimental results show the effectiveness of such a composite for increasing both strength and ductility performances of strengthened columns. Predictive formulas from the literature and from the Italian guidelines CNR-DT 215/2018 do not perfectly fit the experimental outcomes and do not confirm the strength increase of the confined columns. The reason can be attributed to the very low mechanical properties of the natural matrix used to form such a composite. Therefore, considering that the use of a natural and sustainable matrix fully compatible with the masonry substrate is a fundamental requirement for strengthening masonry columns of buildings belonging to architectural heritage, an additional future effort should be made by researchers involved in this field. In particular, for a reliable prediction of the strength of masonry columns confined with composites made of natural matrices, wider experimental campaigns are necessary to refine available formulas with respect to different substrates and component materials.

The floors of Smolensk churches of the 12th–13th centuries

In 17 of 21 Smolensk’ 12-13 century buildings there were found floor remains with different state of preservation. Some were found quite intact in significant area in situ, and other are represented with single findings of glazed tiles. Neither smalt, nor slate slabs were used in that buildings. In two churches there were found sandstone slabs, imitating the slate. In another two churches was mainly used lime mortar grouting. The most widespread materials for the decoration of the floors were the plinth and the glazed tiles. The plinth was mostly used for decorating of the main area of the buildings, for example, in naos and galleries. The glazed tiles more often were found in the separated compartments: choirs, apses and in some special parts of galleries. There is no great variety of shapes and dimensions of ceramic tiles of that time. The square and triangle ones prevail. Their side dimension is normally 11-12 sm, the thickness is 1,8 – 2,8 sm. This proportion remains unchanged, unlike plinth size, which during 12 century becomes smaller and smaller. And also some figured tiles were found in Smolensk’ buildings of that time.

Lime-based mortars with various binder composition: characterization and freeze-thaw resistance assessment

The study focused on lime mortars with different lime binder types regarding the frost attack effects on their microstructure and mechanical characteristics. The performances of studied mortars in hardened state was significantly influenced by the amount of mixing water and by curing conditions. Inhomogeneous microstructure was observed inside the 360 days old specimens with dimensions 40 × 40 × 160 mm in the case of all lime mortars types. The different state of the binder hardening with respect to various distances from the specimen surface and the different behaviour of matured outer part and immature inner part of lime mortar specimens influenced performed tests and reflected in all results. After 10 and 20 freeze cycles, respectively, the compressive strength of all lime mortar specimens with the hydraulic binder component increased, indicating a beneficial effect of the water on the hydration previously unreacted hydraulic binders. On the other hand, the flexural strength of the frost-aged specimens decreased significantly, indicating the drastic procedure of the test performed concerning lime mortars characteristics, especially when the pure air lime binder was used. Improvement of the testing procedure especially for lime mortars, which are characterized by slow hardening, was recommended.

Mechanical Properties of Reproduced Historic Mosaic Mortar

Mortars containing linseed oil as admixture to lime were identified in several mosaics found in Czech Republic. These mosaics were made around 1900 and the composition of their bedding mortar was likely influenced by publication La Mosaïque by E. Gerspach [1], published in Paris, 1880. The recipe for lime mortar with linseed oil and stand oil has been reproduced within the present paper. Four mixes were prepared with varying oil/stand oil content (below, above and according to Gerspach’s recommendation). The primary motivation of mosaic artists to use oil admixture was to keep the mortar’s plasticity for longer time, what is beneficial for the mosaic tesseraes (stones) adjustment. This effect was quantified by help of Vicat apparatus. The influence of oils on mechanical properties and carbonation was evaluated at 28 days. It was found by XRD, that the rate of carbonation is reduced due to the oil presence. It is caused by fact that the oil acts also as water-repealing admixture what reduces the ability of aerial CO2 to dissolve in pore solution and react with lime. The deformation behavior of material has been modified by oil toward the higher toughness, but lower compressive strength, due to polymeration of oil in mortar.