"Вестник МГСУ"

The authors argue that intensive construction and development operations generate a large number of idle quarries. Now Moscow Metropolitan area has about 2,000 abandoned quarries and in excess of 150 quarries in operation. Most of them were used to develop various minerals, namely, sand, crushed stone, gravel, peat and other materials.Recovery of abandoned quarries and assurance of their safe condition requires a set of actions to be taken. However, mere reclamation cannot resolve all environmental problems arising after the completion of mining operations. Obviously, the use of undisturbed land areas as household waste landfills is not the best idea from the viewpoint of the environment. Therefore, filling idle quarries with specific types of products is an improved method of reclamation of mines and quarries. This method may solve two problems at once: they are land reclamation and safe waste disposal. Sewage sludge generated by households, as well as industrial enterprises, may serve as the solution.In this paper, the authors study the dependence between the permeability ratio, the carrying capacity of different soil mixtures containing sewage sludge to be used as the reclamation agent in the course of restoration of disturbed territories. The authors also consider dependence of concentration of biogases and the phosphogypsum content in biogases.

Obtained building material based on magnesia binder with different content of peat (0 to 90 %), on a specially developed technique. As a binder used PMK 87, for mixing mixtures used aqueous solution of magnesium chloride and peat from the Ivanovo region. It were determined such physical and physico-mechanical properties of the investigated material as the compressive strength and the density. The strength characteristics of silicate bricks, ceramic bricks and the investigated material based on magnesia binder and peat was analyzed and compared. It is established that the samples of construction material with content of peat not exceeding 40 wt.% can be attributed to the materials of structural purpose by its compressive strength. Samples of the material with content of the peat 40% have a density 943,75 kg/m3, that provides good heat and sound insulation properties. It is revealed that the solution of the raw material mixture of magnesia binder, peat, the solution of bischofite is optimized to place, and the material gets at least 85% of its strength during 30 days.

The authors consider the strength development of sandy soils in the contest of the physical chemical theory of effective stresses. The authors drive particular attention to the assessment of formation of various types of energy contacts in sandy soils. The article is based on the overview of theories developed by several researchers, on the one hand, and on the findings of the experimental research of sandy soils that have different structural patterns, on the other hand. The experiments include both those that were held a while ago and the most recent projects. The authors have proven that the strength of sandy soils is, to a significant extent, driven by their morphological peculiarities that determine their condition in the context of the assessment of their “densitymoisture”. Strength values of sands are dependent on their moisture content both in terms of their maximal shear stress values obtained in the course of shear testing, or their per-unit penetration resistance, penetration values, as well as the inner friction angle and cohesion. The “strength-moisture” is presented as a curvilinear graph that has two upper limits, one for shear tests and the other one for penetration tests. Maximal strength, according to the shear test, is attained for dry sands, if their moisture content is close to the “optimal” value. As for the penetration tests, maximal per-unit resistance to penetration and penetration values are also close to the “optimal” moisture content value. The authors have identified that moisture content is an important factor of strength of sandy soils that demonstrate various structural characteristics.However, the process of formation of structural peculiarities of sands, namely, their morphological parameters and the nature of the surface of sand particles is influenced by the presence of various films on the surface of sand particles. The article represents a preliminary analysis of the theoretical and experimental findings, therefore, any discussions are welcome.

The paper deals with the formation of limiting bulk densities of sandy soils of different origin against different values of humidity and varying structural features. The authors have identified that the optimum moisture content is typical for sands and clays exposed to mechanical compaction. The nature of this dependence is different from the one between the density and humidity of clay soils. These differences are driven by the peculiarities of formation of bound water shells in the event of low humidity. A linear dependence between the optimal humidity of sands and maximal molecular moisture capacity has been identified. The authors make a statement based on the proven de
pendence between the maximal molecular moisture capacity and the morphology of sands. Their statement is that the formation of bound water shells in the low humidity environment is dependent not only on the fineness of particles, but, to a higher extent, on the peculiarities of the shape and the nature of the surface of sand grains. Another important factor of impact on the density of sandy soils in the natural environment consists in their humidity.
Multiple researchers believe that the correlation between density and humidity of sands is to be the subject of research. It is noteworthy that limit densities of air-dried sands are to be assessed. Therefore, any sands have some particular bound water content, and the lower the intensity of treatment of sand particles, the higher the water content. The findings demonstrate that in most cases typical coagulatory and transitory contacts of non-saturated sands are to be considered in line with the ideas expressed by V.I. Osipov, as the above contacts determine the formation of effective stresses from the prospective of the physicochemical theory.

Introduction. The paper presents theoretical and experimental studies of the improvement of the structure of lightweight concrete, which provides the maximum value of the attenuation of the amplitude of external air temperature fluctuations during the passage of heat flow through the walls and the reduction of thermal conductivity, the results of the 3-factor experiment on determining the rational structure of claydite concrete and the methods for their processing. To determine the purposeful structure of the composition of lightweight concrete and its thermal conductivity, a complex of research works was carried out at the Central Research Institute for Housing, applied to lightweight concrete for exterior walls. The main optimization criterion was the maximum reduction in thermal conductivity while providing the necessary strength, durability and waterproofness. The purpose of this work is theoretical research and experimental substantiation of methods for improving the structure of lightweight concrete used for a hot climate with improved functional performance. Materials and methods. As material a claydite gravel with bulk density p = 400 kg/m3 of Lianozovsky plant (Moscow) was used, at a ratio of 40 % of the fraction 5-10 mm and 60 % of the fraction 10-20 mm and a Portland cement of the brand “400” of the Voskresensky plant, not plasticized. The water flow rate was varied for 10 seconds, to ensure the mixture to be vibropacked.As a foam generating agent and plasticizer, the “Saponified wood resin” (SDO) was used in a 5 % aqueous solution. The methods were adopted in accordance with the Recommendation on the technology of factory production and quality control of lightweight concrete and large-panel constructions of residential buildings. M. CNIIEP dwelling, 1980. In the department of the lightweight concrete application at CNIIEP of dwelling, a method for the purposeful formation of the structure and composition of lightweight concrete, which provides a set of physic-technical, technological and technical-economic requirements, was developed. Results. Calculations are reduced to obtaining mathematical models of dependence of strength R, density ρ, thermai conductivity λ and other indicators of concrete characteristics from initial factors in the form of regression equations. Based on the equations obtained, it was possible to determine the expedient composition of lightweight concrete, which, in combination with the operational characteristics, provides comparable results of the technical and economic characteristics of a single-layer structure from the projected type of lightweight concrete. Conclusions. 1. An improved composition of the structural and heat insulating lightweight concrete for the load-bearing part of the structure, providing its high thermal stability by chemical additives and low consumption of porous sand, was developed. An algorithm for selecting its composition on computer is made. 2. The conducted researches in the field of design of external enclosing structures for hot climate conditions have shown that: single-layer exterior wall constructions with massiveness of D ≤ 4 provide minimum allowable values of heat flux attenuation and temperature fluctuation amplitude on the inner wall surface.