Determination of the resistance of building composites under different types of freezing

The object of the study is the processes of structural degradation and changes in the physico-mechanical properties of cement paste, cement–sand mortars, and concretes under cyclic freezing–thawing under different exposure conditions. The problem considered in the study is the insufficient compliance of traditional methods for assessing frost resistance with real freezing conditions. Most structures in the natural environment are subjected to one-sided or local cooling, rather than comprehensive. The article analyzed building composite materials: cement stone, mortars and concretes, as the object of the study. These materials are most often subjected to prolonged climatic influences during their operation. The obtained experimental results give grounds to conclude that the conditions of exposure to negative temperatures on products and structures play a significant role in their ability to resist frost damage. A comparison of different freezing conditions showed that with local exposure, the zone with higher humidity is destroyed more intensively. This indicates that traditional methods for assessing frost resistance, which are based only on comprehensive freezing, do not fully reflect the real operating conditions of structures. Quantitatively, it was shown that after five freeze–thaw cycles, the damage coefficient under local exposure was about 30% higher than under uniform (all-sided) freezing. The obtained results showed the need to develop recommendations for assessing the frost resistance of building materials depending on the operating conditions of the objects for which they are intended. Taking into account the identified dependencies in the current regulatory documents will allow for a more differentiated assignment of requirements for frost resistance of materials, which will inevitably lead to a decrease in the material intensity of products while simultaneously increasing the level of safe functioning. This is the practical significance of the research carried out. The proposed approach allows for a more objective assessment of the frost resistance of building materials, which will contribute to increasing the durability of structures and reducing the material intensity of products without losing the level of their reliability