Loading of reinforced concrete structures in the early stages of hardening causes the development of inelastic deformations that fade with time. Considering the intensive flow of shrinkage deformations during this period, an important role is played by taking into account the effect of moisture on the structure of composites subjected to early loading. The review of works on the study of the dependence "moisture of cement stonedeformation of creep" is given. Since the creep strains, in turn, are influenced by the parameters of the early loading (age at the time of loading, the magnitude and duration of the load), it is appropriate to assume a connection between the moisture content of the cement stone being loaded and its properties after the load is removed. Based on the author's already available data, a comparative analysis of the phase composition of loaded and unloaded samples was performed using XRD and DTA. On the X-ray patterns of loaded samples, the height of the peaks of the main minerals decreases, which may indicate an increase in the degree of hydration. Peaks of ettringite, as well as CSH hydrosilicates, have a higher intensity when analyzing samples after the early loading. Despite the noted aspects, the main peaks related to portlandite, when the load is applied, decrease. An assumption has been made that this phase is bound by sulfate constituents. The arc of amorphousness of the loaded sample lies below the control one, which indicates its lesser amorphicity. Differential-thermal analysis as a whole correlates well with XRD data. Derivatograms of loaded samples indicate their increased humidity, and the determination of portlandite content by mass loss in the range 430-470 0 C showed a decrease in this phase with the early loading of cement stone.

The purpose of this study is to select the best methodologies for determining the condition of concrete structures. Semi-destructive concrete exposure methods were used to determine resistance parameters: the impact echo test to determine internal structure, the Figg test for air permeability, the initial surface adsorption test for water adsorption, titrimetric for chloride amounts, and a chemical and physical method to determine carbonation levels. In addition, two situations were simulated: a fire and a pipe burst and their impact on the condition of reinforced concrete structures. It was shown that the exposure to temperatures decreases the level of acidity, resulting in increased corrosion of steel. During a pipe burst, the amount of chlo-rides increases, which affects the reinforcement, oxidizing it. A search for possible correlation between concrete structure and carbonation, air permeability and water adsorption was also carried out. It was found that there is an almost linear dependence of these parameters on the presence of cracks, the deterioration of the structure leads to an increase in the transport properties of concrete, which becomes a danger to steel.

Additive manufacturing (3D printing) is becoming more and more common in the field of modern construction. However, for wider implementation of this technology, it is necessary to solve a number of material-oriented scientific problems related to development of concrete composition with targeted rheological, stress-strain, physical and mechanical properties. It has been established that time periods between successful applications of layers play the crucial role in ensuring monolithic features of the “printed” structures. Application of mathematics planning of the experiment allowed establishing the main principles of formation of basic physical and mechanical properties of fine-grained concrete depending on material composition.

The article deals with the results of comparative tests of the phase composition of cement stone distinguished by strength under bending and compression. The comparison has been made between samples subjected to early loading and control samples. An increase in tensile strength in bending of samples subjected to early loading was recorded. The difference in compressive strengths does not exceed 5%. X-ray phase analysis indicates amorphous phase increase with the growth of strength properties, which is manifested in increased intensity of the amorphous phase arc in the X-ray diffraction pattern. The highest peak of the curve corresponds to the maximum flexural strength of the entire row of samples. Among the samples subjected to early loading, the peak intensity of the group of crystal tobermorites with interplanar distances 11.5-11.3Å and 12.5Å appeared to be higher than the intensity of the control samples. It was proposed that the amorphous structure affects the increase in tensile strength in bending of cement stone subjected to early loading.

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