Papers by Keyword: Composition

Abstract: The paper comments on the influence of various technological factors influencing the values of elastic modulus. Today, the composition of concrete combines the classic input components with the significant use of mixed cements, active admixtures and superplasticizers in order to achieve the required compressive strength of concrete and durability while reducing costs. On the other hand, the composition of these concretes has a negative impact on the elastic modulus which are significantly lower than the values derived from compressive strength in Eurocode 2. At the end of the article is a list of measures that are a prerequisite for obtaining the required concrete elastic modulus.

Abstract: In the work the bituminous-polymeric composition stable against action of external factors is designed taking into account literature-patent researches and industrial needs. The basic physical-mechanical and thermophysical properties of the designed bituminous-polymeric composition are investigated, and also change of water absorption, shrinkage with time and flammability is studying. The technology of manufacturing bitumen-polymer composition in production is described. The designed bituminous-polymeric composition on some indicators, in particular on heat resistance and flexibility is better than existing analogs that allows its introduction.

Abstract: In this work, a high-entropy alloy and CrZrTiNiCu coating were synthesized by mechanical alloying. It is shown that the microhardness of the CrZrTiNiCu coating is not inferior to and in most cases exceeds the hardness of high-entropy equiatomic alloys. The wear resistance of such a coating is 3·10^-4 g/min, which also corresponds to special steels in terms of wear resistance. The high-entropy coating has a low coefficient of friction. It turns out to be antifrictional, which obviously leads to energy savings. For the first time, the surface energy, contact potential difference and work function of electrons for CrZrTiNiCu coating were determined.

Abstract: Locally produced crucibles in Ghana experience dimensional failures during fire assaying of ores, therefore, even with a higher cost, imported crucibles are still the most preferred choice by laboratories in Ghana because of the stable performance of up to three cycles. Assay crucibles of locally manufactured, imported and theoretically composed were sampled and analysed via reverse engineering to identify factors that are attributed to the failure during use. Field investigation and compositional, physical and structural investigations were carried out using XRD, water boiling and SEM-EDS analyses, respectively. The results indicated that failure of the local crucible can be attributed to low mullite phase in both content and planes, which could ease the crack development and enhance the thermal stability of the crucible; non converted quartz into cristobalite, which stabilises the volume expansion coefficient during the fire assaying cycles; excess quartz content and absence of alumina content weakened the corrosion resistance against attack from the basic flux of litharge; and high porosity, allowed penetration of molten charge into the structure of crucible, leading to the dissolution of free silica content into the charge and causing structural failure. To overcome such deficiencies, higher firing temperature (~1240 °C), extra soaking time, and blending of high alumina contained clay/minerals were suggested.

Abstract: A directed modification of the formulation of industrial PVC plastic brands I40-13A was carried out using zinc borate, antimony oxide and chalk. It was found that the introduction of these additives into the compound can significantly increase the values of the oxygen index and the coke residue of the initial PVC plastic. It was found that a modification of the formulation of industrial PVC plastic leads not only to an increase in fire resistance, but also to a noticeable improvement in the basic physical and mechanical properties of the compound. It is shown that with a slight modification in the formulation of industrial PVC plastic compound it is possible to obtain materials that meet fire safety requirements

Abstract: The current state of the cosmetology industry in the field of eyelash extension services is analyzed. It is concluded that the popularity of this type of service, despite the negative impact on eye health, will grow in the near future. The main symptoms that occur when using this procedure are analyzed. Among the most common symptoms should be noted a feeling of heaviness of the eyelids, burning, discomfort associated with a decrease in the field of view. It is noted that despite a number of works in this area to date, there is insufficient research, both from the point of view of the analysis of clinical cases, and from the point of view of developing safer adhesive compositions. An analysis is made of the characteristics of adhesives used in domestic cosmetology rooms. At the same time, attention was paid to the following: country of production, composition, texture and texture, setting speed, wearing time, shelf life, recommended temperature and humidity level. A typical composition of glue for eyelash extension contains the following components: cyanoacrylate and its derivatives (± 90 %); polymethylmethacrylate (PMMA) (± 6 %); black pigment - carbon black (± 4 %).

Abstract: The results of selection and principles of calculating the ceramic masses composition for the clinker tiles’ production from argillites taking into account the raw materials’ characteristics are presented. The positive properties of argillites, as well as the properties that do not allow the tiles’ production of by stamping, which is traditional for these products’ manufacturing, are noted. Having low sensitivity to drying, low air shrinkage, high strength of the calcined shard, while being fusible sintering raw materials, argillites are low plastic and have insufficient bonding during molding, which indicates the need for corrective additives. In this work, the task to select the composition of ceramic masses to increase the plasticity of argillites while maintaining the positive properties of the main raw material was set. The authors proposed the use of siliceous clays as a corrective additive. An integrated approach was applied in calculating ceramic masses by grain composition and chemical and mineralogical indicators. Based on the research of A.I. Avgustinik, the oxide content Ca, Mg, Fe, Na, K and attitude Al₂O₃/SiO₂ was taken into account. In order to obtain the densest packing, when calculating the grain composition, the natural dispersion of siliceous clays and the grain composition of previously prepared argillites were taken into account. The obtained theoretical calculations were tested in practice. Practical results showed that the 15% introduction of siliceous clay with the ceramic mass composition made it possible to obtain clinker tiles with improved physical and mechanical properties.

Abstract: The influence of the glass powder dispersion and its amount on the operational properties of glass-reinforced concrete is investigated. Box and plate glasses, which were crushed and ground in a ball mill, were used as the starting material. Portland cement manufactured by Serebryakovcement, a brand of CEM IIA 42.5N, was used as a binder. The developed technology for the glass-reinforced concrete manufacturing provided at the final stage for a joint grinding of Portland cement and glass powder. At the same time, the specific surface area of ​​Portland cement increased from 3200 to 6500 cm²/g. The optimum amount of fine glass powder in glass-reinforced concrete is established. It is shown that at the content of 30 wt.% glass powder with a dispersion of 5872 cm²/g the glass-reinforced concrete density is 1915 kg/m³ and the compressive strength is 45.09 MPa. When superplasticizer is introduced into glass concrete, a synergistic effect is observed, as a result of which the compressive strength increases to 50.88 MPa. Using the synchronous thermal analysis, the effect of finely dispersed glass powder on phase transformations in glass-reinforced concrete under non-isothermal heating conditions was studied. It was shown that the processes of ettringite dehydration in glass-reinforced concrete are shifted to the region of high temperatures, and the processes of calcium hydro silicates dehydration and calcite destruction are shifted to lower temperatures.

Abstract: Reftinskaya state district power plant owned by Enel company and located in Russia produces up to 5 million tons of fly ash and slag annually when burning multi-ash coal of the Ekibastuz basin. A new system of dry ash removal works at the power plant; it includes the laying system of wet ashes and slags on the dump and the discharge system from the silo storage facility up to 1 million tons of ash per year. The chemical-mineral and grain composition data, properties and their correspondence to Russian standard 25818 in order to use ash in the production of concrete and products based on it are presented. The experience of production and application of autoclaved aerated ash concrete of reduced density is considered. It is shown that fly ash of Reftinskaya state district power plant is an effective substitute for quartz sand in the technology of cellular concrete. Its application opens up additional opportunities for aerated concrete with a density of 300-400 kg/m³ production. To optimize the structure and properties it is proposed to introduce an additive of natural gypsum in the amount of 3-5 % of the mass of dry components into the autoclave aerated concrete. The produced aerated ash concrete had a thermal conductivity of 0.075-0.100 W/m∙K which allows it to be used for erection of single-layer enclosing structures without additional insulation. Fly ash can also be used as part of heavy and fine-aggregate concrete replacing a part of Portland cement and sand. The addition of ash in an amount of up to 25 % by weight of cement improves the workability and reduces the demixing of the concrete mix. Ash introduction up to 10 % increases the compressive strength of concrete at an early time and after 28 days of normal hardening, an increase of it up to 25 % decreases the compressive strength, reduces the conductivity, but increases the shrinkage of concrete. The optimum ash content up to 100 kg/m³ for steamed concrete and not more 50 kg/m³ for normal hardening concrete. Compliance with the optimal composition and technological parameters of the production of concrete structures using ash enables to produce concrete of F200-F300 grade by frost resistance.

Abstract: The development of the fuel and energy complex entails a direct increase in energy consumption and the development of fundamentally new types of resources. In the near future, it is predicted that the role of solid fuels, including low-grade ones, will increase in the country's fuel and energy balance, which is primarily due to their large reserves. Russia ranks third after the USA and Brazil in the world for this mineral and, according to the latest estimates, potential reserves of this raw material are in the order of 700,288.85 million t. The article is devoted to the analysis of the chemical composition of oil shale of the Leningrad field. The point microanalysis of oil shale was carried out on the scanning electron microscope TESCAN, and IR spectra of various functional groups that are part of the shale were obtained and analyzed. It has been revealed that the functional groups C-C, C=O, CH₂, CH₃, SH are typical for the organic component of the oil shale of the Leningrad field. Carbonates, silicates and hydroxides mainly represent the mineral part with impurities represented by phosphates, sulfides and sulfates.