Deterioration of historical materials with mineral binders in buildings of architectural heritage can be influenced by several different factors, which are often the result of changes in the environment where the buildings are located. In order to analyse the damages of these materials and the causes for their occurrence, three buildings of architectural heritage located in three different climatic zones were subjected to visual analysis and non-destructive testing using 3D microscopic system HIROX. In all the analysed buildings we found similar causes of the observed damages of architectural surfaces (biodegradation, salt crystallisation, moisture, etc.), regardless of the climatic zone. We also found that with the 3D microscopic system HIROX we can monitor opening/closing and progress of surface cracks, carry out analyses of the cracks, and also monitor the crystallization and dissolution of the surface salts, all these in-situ. On the samples of materials with mineral binder taken from the buildings we performed (where possible) petrographic analyses with an optical microscope and X-ray and TGA analysis in order to characterize historical mortars and determine the causes of damages. Reaction rims were observed on samples of masonry mortars from the Kolizej palace and they attracted our attention. In continuation of the doctoral dissertation we prepared replicas of analysed historical render-masonry-plaster composites and mortars for accelerated aging tests. To study the impact of crystallization and dissolution of salts on the render-masonry-plaster composites we developed accelerated test that allows continuous monitoring of the development and progression of damages with the 3D microscopic system HIROX. To study the reaction between mineral binder and dolomite aggregate grains observed in masonry mortar from the Kolizej palace, samples were prepared from six different mortars. As an aggregate we used inert limestone or selected dolomite grains, and as binder lime putty, lime putty with tuff or pure Portland cement was applied. Samples were exposed to different accelerated ageing conditions (a solution of deionised H2O or 1 M NaOH, and a temperature of 20 °C or 60 °C). On the samples mechanical tests and measurements of the modulus of elasticity, change in weight and length of the samples, as well as optical and electron microscopy (SEM) analyses were simultaneously carried out in prescribed time intervals up to one year. The results of the tests show that the alkaline carbonate reaction (ACR) occurs between the used dolomite aggregate and binder, and its progress influences changes of the mortars’ microstructure and thereby also changes of mechanical properties. ACR is manifested as a dedolomitisation process, which takes place in investigated mortars in different stages. The lowest level is dissolving process along the boundaries between dolomite crystals, called selective dedolomitisation. In the next stage reaction rims are formed. Under an optical microscope, the
rims can be seen as a change in colour of sparite crystals from white to brown and under the SEM as a typical myrmekitic texture. Through the progress of the ACR, secondary calcite ("Ca halo") is formed in the binder, close to the modified parts of dolomite grains, and a "new phase" on the edge of the modified parts of dolomite grains. ACR occurs and progresses regardless of the binder type, but the dynamics of reactions and the formation of "Ca
halo" and "new phase" depend on the type of binder. Diffusion of ions shows that the system is dynamic and changes with time. The temperature and selected aqueous solution influence the ACR progression.