Study of the mineralogical and grain size composition of the regenerated grain from bearing sludge

The composition of sludges (wastes of bearing industry enterprises) is determined by the characteristics of the abrasive tool used upon manufacturing, grade of the processed material, cutting-tool lubricant (CTL) and modes of treatment. We present the results of studying the mineralogical and grain size composition of the regenerated grain from bearing sludges. The material under study is shown to have the following composition, %: abrasive particles — 5 – 8, metal particles — 50 – 90, binder — 2 – 5, balance — SOG, oil and various pollutants. The dispersion of solid particles ranges within 0.1 – 0.3 mm. The abrasive grains have a predominantly splintery shape, the individual binder particles being observed on their surface. The interlayer-cemented aggregates of two — three crystals and a large number of small splintery particles are also present. It is shown that the samples with a regenerated material containing fine abrasive grain and metal particles as a filler exhibit the highest mechanical strength and thermal conductivity. The results obtained can be used when using regenerated abrasive grain from sludge for manufacturing, e.g., grinding wheels, preparation of a molding abrasive mixture, etc.

RESEARCH OF THE DEPENDENCE OF THE GRAIN SIZE COMPOSITION AND GRADE OF CRUSHABILITY OF RECYCLED CRUSHED STONE ON THE STRENGTH OF THE ORIGINAL RECYCLED CONCRETE

The results of the study of the grain-size composition and the grade of crushability of recycled crushed stone and their dependence on the strength of the original recycled concrete are presented. It is found that recycled crushed stone obtained from the original concrete of classes B10 - B30 does not meet the requirements of GOST 8267-93 for total residues on Ø25, Ø20, Ø5 and Ø2.5 sieves. Regardless of the strength of the original concrete, the main fraction of recycled crushed stone is grains with sizes from 12.5 to 20 mm. The strength (grade in terms of crushability) of the recycled crushed stone increases with an increase in the strength of the original concrete. The study of the main parameters of recycled crushed stone at the current moment has been carried out in an insufficient (for widespread introduction into production) volume and requires further study for the subsequent development of independent regulatory and technical documentation (or additions to the current regulatory and technical documents).

CONFORMITIES TO LAW OF FORMING LAYER FOR POLYDISPERSE PELLET CHARGE ON SINTER BELT

Motion of pellet charge on the loading tray on a sinter belt is accompanied not only by the change of its grain-size composition, but by segregation processes, id est. by the redistribution of charge of different size particles for the most part friable material. The result of this process is formation of local discontinuity with pre-dominance of content for particles of certain factions. The traditional method for analysis of work for loading tray on the basis of factious classification does not allow to educe and analyze appearing heterogeneity in the most part friable material. It results in errors at the calculation for action of the system of the automated control by sintering process and ignoring of notational of the use of segregation of particles of friable material for optimization of technological process. The use of balance method enables to specify and spread understanding of mechanism of processes which take place during motion of pellet charge in relation to the loading tray, and also to form theoretical pre-conditions for the choice of the rational modes of operations of agglomeration separation of sintering plant. It is set that at monotonous increase of angle of slope for loading tray the segregation phenomena increase in a pellet charge, and after achievement of the defined value – go down, id est. have extreme character. Mentioned features of forming of layer for polydisperse material in the conditions of inconstancy of mechanical properties of its separate factions it is possible to take into account at the use of balance of grain-size composition of charge, loaded on a sinter belt, and charge, being on it, when conditional middle diameters of particles of their components must be equal. On the basis of the set conformities to law of forming of friable of structure of layer the method of authentication of grain-size compositions of pellet charge mixture is in theory reasonable in every its horizon taking into account a segregation during loading.

Evaluation of mechanical properties of concrete produced with binary and ternary mixtures of aggregate

Cement is the costlier component of concrete, and its productive process causes considerable environmental impact. Thus, alternatives are studied to reduce the amount of cement used. An option is the use of optimized grain size curves of aggregates, aiming to achieve a higher compactness of concrete. An ideal grain size distribution results in a higher mechanical resistance of concrete, providing a reduction in cost and consumption of materials, and, consequently, in environmental impacts. Therefore, the present study aims to improve the properties of conventional concrete through optimized grain size distributions. In this research, concrete was produced with binary mixtures with rolled pebbles from Belém region, in Pará state, and ternary mixtures of granitic crushed stone from the metropolitan region of Recife, in Pernambuco state, and concrete properties in the hardened state were studied. The mix design IPT/EPUSP method was used and grain size composition, unit weight, water absorption by capillarity, and compressive strength tests were performed. It was observed an increase in compressive strength with for higher fine contents. Furthermore, for both aggregates studied, there was no loss in strength with the lower amount of cement used, due to the increased compactness of the concrete, indicated by the unit weight of the aggregate mixture. Therefore, the optimization of the grain size composition of the coarse aggregate provided a reduction in the cement consumption for the same required strength and for both analysed aggregates.

Study Of Structural Properties And Flame Of Vollastanite, Dolomite, Vermiculite Minerals

This research paper analyzes the structural properties of vermiculite, including its bulk density, grain size composition, porosity and intergranular voidness. In addition, the results of relevant scientific experiments are presented, proving a higher degree of thermal insulation of vermiculite in comparison with other thermal insulation materials.

SEDIMENT GRAIN-SIZE COMPOSITION IN LAKE ANASHKINO (SOUTH-WESTERN ONEGO AREA)

The lithostratigraphy and grain-size composition of sediments in Lake Anashkino (south-western Onego area) are described. The younger, upper sediment layers showed a prevalence of very fine sand. Further down the sediment, there dominate coarse and medium silt fractions, and down from the depth of 10.03–10.16 m — medium and fine silt. The oldest sediments (at 10.19–10.20 m) feature a prevalence of very coarse and coarse silt, and further below (10.30–10.31 m) there prevail very fine sand and very coarse silt fractions. The prevalent activity in the palaeo-hydrodynamic environments in which the ancient sediments (9.96–10.31 m) were deposited was turbidite flows. Younger sediments (9.32–9.92 m) were deposited in the environment of low-velocity flows. The sediment formation pattern in Lake Anashkino during the change from a nival to a humid climate suggests there happened five shifts in dynamic water regimes.

THE EFFECT GRAIN-SIZE COMPOSITION ON THERMAL CONDUCTIVITY OF SANDY SOILS

Today the issue of energy saving is acute. The main sources of energy are radiant energy of the Sun, wind energy, energy of moving water. Therefore, the issue of solving alternative energy sources is relevant. The article aims to solve the problem by using low-potential heat of the soil mass by means of energy-efficient building constructions - foundations. It is necessary to know the thermal characteristics of soils for this. At the moment, methods for determining the thermophysical properties of inert materials with subsequent practical application in the field of construction have been widely studied, but no one of these methods takes into account the grain-size composition. Thus, the study of the connection between the thermal conductivity and the grain-size composition of the soil is important. The aim of the work is to Estimation of thermal conductivity of sandy soils based on grain-size composition. This article presents an analysis of the dependence of the thermal conductivity of the sandy soil of its grain-size composition. The matrix of experiment planning is made; the methodology and technological sequence of the experiment were tested. Statistical processing of the obtained experimental data was carried out. Based on a series of test experiments, it was concluded that there are two factors competing in its thermal conductivity: an increase in λ due to an increase in the degree of pore filling and a decrease in total heat conductivity due to a decrease in the degree of pore filling. These results suggest that grain-size composition has an impact on the thermal conductivity of the sandy soil. During the experiment, the dependence of the thermal conductivity of sandy soils on their grain-size composition was experimentally established.