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One of the primary and still unresolved problems of shotcreting is the high rebound rate of the material, which reaches over 20% in “dry” shotcreting. There is a practical need to improve the very principle of shotcreting and methods for optimizing the movement of torch particles. Materials and Methods: The purpose of this study was to justify the use of the electrostatic treatment of cement–sand mortar in the process of performing shotcreting works using the dry method. It was proposed that the binder and then the finished mixture be ionized step-by-step (by passing it through a non-uniform electrostatic field formed by corona electrodes). As a result, the shotcrete will be held on the fence. Results: Analysis of the modeling results shows that the presence of an electrostatic field slows down the particle and reduces the kinetic energy of the rebound. After theoretical calculations, experiments were conducted, during which, the torch size and the plant productivity were changed, and the rebound mass was weighed. After application to the surface, prototypes were formed and subjected to strength tests. It was determined that gunning in a sharply non-uniform electric field demonstrates its practical and economic efficiency due to the uniform deposition of charged particles on the treated surface and low power consumption. Conclusions: It was established that the electrostatic treatment of a cement–sand mixture during application allows concrete particles to be retained on the shotcrete surface, the rebound of the material to be reduced and the strength of concrete to be increased.

The co-authors have proven that the analysis of values of obsolescence indicators applicable to buildings and other facilities in the urban environment allows to make resource-saving decisions in terms of their integrated renovation. At the same time, the need to develop a methodology for evaluating the functional obsolescence of a residential building is also substantiated, as it is the most important component of the concept of comfort of a residential building. A brief analysis of the concepts of “comfort” and “accessibility” in relation to residential buildings is performed. The characteristic of comfort is proposed to be defined using the consolidated indicator of functional obsolescence and physical deterioration of a building. A specific mathematical formula for calculating the parameters of comfort is provided, depending on the consolidated characteristics of indicators of physical deterioration and obsolescence of a building. The proposed analysis of principal obsolescence evaluation methods, applicable to residential buildings, allows to identify the main weaknesses of currently used methods. As a methodological approach to evaluating the obsolescence of a residential building, a systematic approach is proposed that allows a comprehensive, structural and quantitative assessment of obsolescence indicators through the use of mathematical methods, including the method of expert assessments and a modified verbal-numerical scale, initially developed by Harrington. A systematic hierarchical relationship between general and specific indicators of obsolescence of a building is identified. A systematic approach is employed to develop a procedure for identifying the integral obsolescence of a building with regard taken of the hierarchical relationship between its specific and general indicators. Pie and bar charts are used to analyze alternative building obsolescence evaluation methodologies. A detailed description of the proposed option is provided in the form of specific examples. Acknowledgement. This research was supported by Project No. 3.1.1.1 within the 2021–2023 Plan of Fundamental Research of the Russian Academy of Architecture and Civil Engineering and Ministry of Civil Engineering and Public Utilities of the Russian Federation.