"Вестник МГСУ"

According to the authors of the article, it has been proven that dry and damp materials crushed in grinders of the shock type demonstrate different grinding patterns. Therefore, there is a need to explore the influence of the moisture content produced on the efficiency of grinding. The most efficient grinding mode is the one that assures maximal probability of destruction.
Centrifugal grinders were used to analyze the grinding process. The experimental data have proven that the probability of destruction of damp samples is a lot higher than the one of dry samples, given the same initial dimensions of particles and the loading intensity.
The rise in the probability of destruction is stipulated by the fact that that the grinder speed at which crushing is triggered is lower in case of damp samples than in case of dry ones. Expressions for speed that describes destruction initiation and the probability of destruction depending on the type of materials, the moisture content and the loading intensity have been derived.

The objective of this research project is to substantiate the optimal values of disperse calcium
carbonate waste materials, to ensure their granulation into artificial stone, and to substantiate the
output rate efficiency.
In the course of the research, the authors assessed the lump-forming rate demonstrated by
calcium carbonate waste materials and cement grade CEM I 42,5 N on the basis of their molecular
and capillary moisture capacity. The assessment methodology that defines the threshold of the
lump-forming capacity, as well as the coefficient of output of man-made gravel for different dispersions
of calcium carbonate waste materials have been identified. Data reliability is based on the
mapping of the nature of dependences between the coefficient of lump-forming and the coefficient
of gravel output on specific surface areas.
The authors have identified that calcium carbonate waste materials have a lump-forming factor
that is close or equal to 100%, if its dispersibility is equal to 400-600 m2/kg. In this case, the
highest lump-forming rate is accompanied by the waste fineness of 500 m2/kg.

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.