Optimization of compositions and technology of production of small-clinker floured cements using the most effective fillers

Considering the physical chemistry of grinding it is worth quoting the grinding of mineral building material as “the change of physical-chemical properties of finely ground materials can not only be due to the reducing the particle sizes, at mechanical grinding significant changes of the crystalline structure of their surface layers (thickness 15-20 microns) take place, in many cases the technological properties of fine powders are not so much due to dispersability but are namely due to the structure rupture”, at that the energy costs for this are “significantly greater than for the exposal of surfaces with a clean cleavage”. The speed of heterogeneous chemical processes involving fine powders is determined primarily not by the magnitude of their specific surface area, as commonly is believed, but by the decrease of energy of activation as the result of crystalline structure rupture and amorphization. However, both specific surface area and energy demands to achieve are actual evaluation of the effectiveness of any material grinding at a particular unit. The main factor of the production process of cements of low water demand is the grinding, characterized by grindability.

Numerical analysis of pile foundations in seasonally freezing soil ground

The article presents the results of numerical analysis for pile foundation in seasonally freezing soil ground. This project uses the static tests of soil by piles at the construction site of Cargo off-loading facilities (Prorva, Atyrau region, Kazakhstan). The project area is located along the east coast of the Caspian Sea, both onshore and offshore, near the Prorva oilfield, Kazakhstan. At present, the North Caspian Sea has a limited water depth (max 8 m). According to the test results have been made design changes in the pile foundation. Static tests (SCLT) were carried out on the piles with 16m in length and precast concrete joint pile foundations with a total length of 22m to 27m. This research is important for an understanding of the interaction mechanism of precast composite joint piles with seasonally freezing soil ground of the Caspian Sea coastal area of the site.

The equilibrium time and deformation characteristic of sulfate saline soil in 1D saline expansion test

The salt expansion disease is serious for the soil containing sodium sulfate in cold regions. This paper carried out one-dimensional swelling tests of saline soil, and numerical cooling tests of soil to explore the stability time of salt swelling deformation and determine the standard procedure of the salt swelling test method. The test results demonstrate that: (A) the temperature equilibrium and crystallization process are almost completed simultaneously in the one-dimensional (1D) salt expansion test; (B) Referring to the standard of consolidation test, a standard that the expansion rate is less than 0.02mm/h can be used in the salt expansion test; (C) The required time for temperature equilibrium of soil is quadratic to sample size and is much faster with liquid bath condition comparing to gas bath condition. Because the deformation and temperature are synchronized, the deformation stabilization time of different size samples in different cooling media is recommended.This can provide a reference for the deformation equilibrium time of the salt swelling test.

Developing a heap leaching technology for floating gold ores

The features of the technology of heap leaching with floating gold are disclosed. It was found that significant technological losses of gold in the processes of enrichment of gold-bearing ores, as a rule, are associated with its natural fine mineralization or technogenic transformation to such a state. It has been shown that flat gold flakes (even with a gold grain size of more than 1 mm) are quite well retained on the surface of technological solutions, i.e., have a certain buoyancy. The wettability of gold particles is explained by the manifestation of the surface tension forces of aqueous solutions, the mechanisms of which are determined by the van der Waals interaction. In addition, the wettability of gold grains is affected by their electric charge, which, accumulating on a convex surface, creates a negative charge that prevents the formation of a double electric field around the gold particle, which is an additional reason for the non-wettability of gold. The mechanism of the formation of gold films, which are formed at a high value of surface tension, with the formation of floating "islands" covered with a hydrophilic shell, is explained. It was revealed that the energy of interaction of a gold nanoparticle with water can serve as a quantitative indicator of the buoyancy of gold grains and "islands" of nanogold, at a value of which of 0.05427 eV, clearly pronounced hydrophilic properties appear. The theoretical substantiation of the buoyancy of gold grains and "islands" of nanogold is the van der Waals interaction. On this basis, heap leaching technology was developed, with the targeted deposition of floating gold in the most suitable places. As a result of a decrease in the surface tension of leaching solutions, nanogold loses their initial buoyancy and sink from them to the bottom, where they will be subjected to the processes of their disembarkation (collection and extraction).

Research of heating the lining of high-temperature units in order to increase their residual resource

The article contains an analysis of the initial stage of the heating process of high-temperature units. The heating modes used at the enterprises lead to various difficulties: a delay in the heating process or heating at a high speed at which mechanical stresses arise and exceed the permissible values. The proposed graphical dependencies for heating allow us to heat up at the highest possible speeds, taking into account the time spent on drying. In this case, the ultimate strength of refractory materials is not exceeded, which leads to a significant reduction in the time for the heating process.

Mathematical support for railway emergency response

The current regulations provide a procedure for notification of the occurrence of railway emergencies, but do not define a procedure for responding to such situations. This can be explained by the fact that such situations are very diverse in nature and scale, as well as in the way they are handled. However, the more urgent is the need for a certain classification, typification of ways to respond to them. In connection with the above, the article shows that in the event of occurrence of WD AS, the head of the operational headquarters in complex conditions of lack of complete and sufficient information on cause-and-effect relations between components of such a situation should take a certain number of individual, collegial, information, organizational, operational decisions aimed at coordination, coordination and management of subordinate control points and response units, which may exceed his ability to make such decisions and / or influence their validity.

Calculation scheme of ground freezing depth in Terskol

During the construction of avalanche-retaining geotechnical structures in mountainous areas comes up the problem of fixing and stability of these structures in conditions of seasonal and/or long-term freezing of the ground. This paper evaluates the influence of snow cover and air temperature on the depth of freezing and soil stability based on the developed calculation scheme for the winter seasons 2015/16-2019/20 in the Elbrus region. The calculation scheme was based on the problem of thermal conductivity of a three-layer medium (snow, frozen, and thawed soil) with a phase transition at the boundary. The heat balance equation included the energy of the phase transition, the inflow of heat from the thawed ground and the outflow to the frozen ground, and, in the presence of snow cover, through it to the atmosphere.

Features of static pile load test

Pile foundations are commonly used in engineering practice to transfer the loads from heavy structures such as high-rise buildings to competent soil strata. In this manner, such complications as unfavorable geological conditions, compressible soil layers, and high levels of groundwater are avoided. Different types of piles are used in construction work. The specific type of pile used depends on the type of loading, the foundation soil, and the location of the groundwater table. The technical progress of large, bored piles and the continuous improvements of construction procedures and piling equipment today have created new possibilities. This paper describes a series of pile load tests that were performed in the capital city of Nur-Sultan, Kazakhstan. The control equipment, technological features are important for detailed information about the process of testing and the associated results make them more accurate and reliable. Keywords: pile, static test, load, equipment, soil

Methodological basis for the conversion of transport diesel engines of transport diesel engines to gas-diesel operation

The expediency of the search, development and use of alternative environmentally friendly motor fuels is scientifically substantiated, the main of which is the use of gas fuel, which is much more efficient than diesel fuel in terms of overall environmental safety. The relevance of the research carried out and the developments proposed in this article will make it possible to realize the fundamental complex advantages of the ecological and operational nature of the use of the gas-diesel cycle of the ICE operation. This is in line with the Paris Protocol on a climate to reduce greenhouse gas emissions to keep the global average temperature rising. The paper describes the main features and methods of converting diesel engines to their compressed natural gas power supply. The advantages and disadvantages of all methods of implementing the gas-diesel cycle on existing diesel installations of low and high power are analyzed in detail. The main operations and changes in operating parameters for each method of implementing the gas-diesel cycle on operating diesel engines are also described. The use of a mixed quantitative and qualitative control of the supply of compressed gas and diesel fuel for various loads of a diesel engine operating on a gas-diesel cycle has been scientifically substantiated. The systematization is carried out and the comparative characteristics of liquid and gas motor fuels, which can be used for the implementation of the gas-diesel cycle in diesel engines, are presented in tabular form, general conclusions are described.

A Proposal of Standard Test Method for Frost Susceptibility of Soil

A recommendation of a standard test method for frost susceptibility of soil is proposed. The recommendation is required in order to have a design technique of common and equivalent quality not only in domestic but international practice. This topic is one of the essential and current objectives of Technical Committee 216 (ISSMGE) and has been discussing to the present. The purpose of the proposed recommendation test method is defined, different methods from several countries are compared, necessary and common articles are selected and some items are specified to discuss. It is expected that this proposal would take a role to be a draft suggestion to promote discussion and achieve a final recommendation.