KINETICS OF RHEOLOGICAL CHARACTERISTICS OF FOAM CONCRETE MIXTURE

The results of experimental studies are presented, the purpose of which was to study the influence of variable formulation and technological factors on the rheological characteristics of the foam concrete mixture, in particular, the structural strength. This is preceded by an analysis of the process of structure formation of cellular concrete. As a result, it is shown that the properties of cellular concrete are determined by the nature of the distribution of the solid component. The structure of the solid phase is formed at the earliest stages of the formation of cellular products and depends on the rheological characteristics of the mortar and cellular mixture. In the technology of cellular concrete, it is important to synchronize the processes of pore formation and the growth of plastic (structural) strength, which is also associated with a change in the rheological properties of the mixture. Using the methods of mathematical statistics, the influence of the content of the filler in the mixture with cement, the content of the complex additive, and the effect of mechanical chemical activation on the kinetics of the plastic strength of the foam concrete mixture were studied. The kinetic dependences of the plastic strength of the foam concrete mixture in the range of 6 ... 24 hours from the moment of manufacture have been constructed. Each of the 15 curves is maximized by a 3rd-degree polynomial. Based on the obtained dependences, they are differentiated between the first and second derivatives. As a result, the equations of the speed and intensity (acceleration) of the plastic strength of the foam concrete mixture were obtained. According to the results of the previous experiment, carried out according to a three-factor plan, a 4-factor plan was synthesized, in which the aging period of the foam concrete mixture was taken as the fourth factor. The calculated theoretical values of the characteristics of the structural strength of the foam concrete mixture were entered into the matrix. As a result, mathematical models of plastic strength, speed, and intensity of plastic strength of the foam concrete mixture were calculated and the influence of variable factors studied on the isosurfaces of these properties was visualized. The analysis of these dependencies made it possible to determine the characteristic recipe and technological conditions for obtaining a foam concrete mixture with the required values of plastic strength.

Changes in the plastic strength of the glaze during storage of glazed confectionery

Выявлены закономерности изменения жирнокислотного состава и пластической прочности модельных образцов глазированных конфет в процессе хранения. В ряду орехового сырья миндаль-кешью-фундук-арахис скорость уменьшения пластической прочности глазури конфет с корпусами на основе фундука и арахиса с использованием глазури лауринового типа составила 71-87 г в неделю, что на 30-40 % больше скорости уменьшения пластической прочности глазури конфет с корпусами на основе миндаля и кешью 42-46 г в неделю. Использование глазури с высоким содержанием элаидиновой кислоты позволяет уменьшить скорость изменения пластической прочности глазури на 23-29 %, по сравнению с глазурью на основе жира лауринового типа. Наименьшее изменение пластической прочности поверхности глазированных конфет (2,8 % в неделю) достигнуто для корпусов из пралиновой массы на основе миндаля и глазури, изготовленной на основе жира с высоким содержанием трансизомеризованных ненасыщенных кислот. Предложенный подход можно использовать для количественной оценки и прогнозирования скорости процессов миграции жиров в процессе хранения глазированных кондитерских изделий. Regularities of changes in fatty acid composition and plastic strength of model samples of glazed sweets during storage have been revealed. In the row of nut raw materials almonds-cashews-hazelnuts-peanuts, the ratio of the rate of decrease in the plastic strength of the glaze of candies with bodies based on hazelnuts and peanuts using lauric-type glaze was 71-87 g per week, which is 30-40% more than the rate of decrease in the plastic strength of the glaze sweets with almond and cashew-based bodies 42-46 g per week. The use of a glaze with a high content of elaidic acid can reduce the rate of change in the plastic strength of the glaze by 23-29 %, as compared to a glaze based on lauric fat. The smallest change in the plastic strength of the surface of glazed sweets (2.8 % per week) was achieved for bodies made of praline mass based on almonds and glaze made on the basis of fat with a high content of trans-isomerized unsaturated acids. The proposed approach can be used to quantify and predict the rate of fat migration processes during storage of glazed confectionery products.

Lime compounds for restoration and decoration of building walls

Information on the effect of a polysilicate solution obtained by mixing liquid glass with a silicic acid sol on the structure formation of lime compositions is presented. It was revealed that the amount of specific heat released when lime is wetted with a polysilicate solution is greater than when lime is wetted with water. This is due to the additionally released heat due to the chemical interaction of lime with polysilicate solution. It was found that the introduction of a polysilicate solution accelerates the development of plastic strength. For comparison, we used liquid glass and a sol of silicic acid as an additive. The synergistic effect of the influence of the polysilicate solution on the structure formation of lime finishing compositions was established, which manifests itself in the acceleration of the set plastic strength in comparison with silica sol and water glass. It has been established that the introduction of a polysilicate solution into the lime mixture formulation contributes to an increase in the resistance to slipping of the finishing layer. The optimal thickness of the finishing layer was determined, which is 20 mm, at which sliding from the vertical surface is not observed.

Glass-Crystalline Materials of a Cellular Structure, Formed by Vibration Foaming Technology

A method for producing cellular materials on a glass-crystalline matrix has been developed. The formation of a porous structure is ensured by the process of gas formation, combined with a vibration effect on the raw mass. The possibility of gaining the plastic strength of the raw mass, sufficient for fixing the cellular structure of the raw material without adding binders, has been established. The main component of the raw material mixture is a finely ground filler, obtained after grinding glass-crystalline frit of a specially selected composition. For its formation pre-compacted raw masses, containing natural silica and glass-forming additives, are heated. There was investigated the joint influence of the compositions formulation and the roasting parameters on the properties indicators of the glass composite.

Synthesis of New Fixings of Mobile Sands

The issues of the synthesis of a water-soluble polymer preparation, which can find application in agriculture as a structure-forming agent of soils and mobile sands to prevent water, wind, mechanical erosion, increase fertility, moisture absorption, moisture retention, consolidation of soils, dumps, and mobile sands to eliminate negative effects on the environment. Maleic acid and acrylamide were chosen as monomers for the copolymerization reaction, and potassium persulfate was chosen as the initiator. As it turned out, an increase in the concentration of the initiator from 0.01 to 0.05% (by weight of monomers) promotes an increase in the rate of the polymerization process, maintaining its value for a longer time, reducing the time of this process from 7.0-6.5 to 5, 5-6 hours. In this case, the yield of the polymerization reaction increased exactly from 81.2 to 96.0% for the reaction with the ratio of starting materials 1: 5. When a small amount of alkali is introduced into the reaction mixture, high molecular weight polymers can be obtained. In this case, the yield of the process increases, and the reaction time is reduced by 2-3 hours. Analysis of the kinetics of fixing processes using synthesized and various other reagents, as well as changes in the plastic strength of sands, showed the dependence of the conditions of penetration of the fixer with the formation of a free flow in space under the influence of gravitational or capillary forces on the type of binding agent and on the composition of the sand itself.

Increase the Performances of Lime Finishing Mixes Due to Modification with Calcium Silicate Hydrates

Lime plaster mixes are becoming more and more popular in the world’s building materials market every year. Therefore, the issue of increasing the efficiency of lime finishing coatings is relevant. The paper aim is the modification of lime binders with specially synthesized calcium silicate hydrates (CSHs). To obtain the CSH filler, liquid sodium glass was used with a silicate module of 1.53–2.9 and a density of 1130–1663 kg/m3. Using differential thermal analysis (DTA), X-ray diffraction (XRD) patterns, synthesized calcium silicate hydrates, as well as dry plaster mixes, and finishing coatings based on using them were studied. The regularities of the filler synthesis were established depending on the temperature, density, and silicate modulus of liquid glass, the amount of the precipitant additive, the rate of its introduction, and the drying mode. As a result of processing the obtained experimental data, a mathematical model was obtained for the composition “lime + CSH”. The phase composition of the filler was revealed, which is characterized by the presence of calcium silicate hydrates of the tobermorite group, a solid solution CSH (B) in the form of a weakly crystallized gel, a solid solution of C–S–H (II), hydrohalites, and calcites. It was found that the use of the fillers into the lime compositions, obtained with the rapid introduction of CaCl2 additive into water glass during the synthesis of the filler, promotes the acceleration of the plastic strength gain of lime compositions. It was revealed that the lime composites with the CSH filler are characterized by reduced shrinkage deformations up to 45%. The introduction of the CSH filler into the lime compositions increases the water resistance of the lime finishing layer by 36%. A technological scheme for the production of the lime dry plaster mixes has been developed; it can be introduced at existing factories of building materials without significant re-equipment of production.

Quality and sensory characteristics of cricket powder (Acheta domestica) based cooked poultry balls

As the population grows, the food industry is focusing on alternative sources of protein as insect flours. Cricket powder (Acheta domestica) is rich source of protein, vitamins, minerals, fatty acids, with little environmental footprint and have potential for processing of hybrid meat products. This study analyzes the impact of cricket powder (CP) supplementation (2% and 4%) on the technological and sensory properties of cooked poultry balls. Addition of CP affects all examined parameters in two ways: decrease aW, L*, a* and b* value and increase pH, water holding capacity, plastic strength (PS) and structural strength (SS). The high PUFA in CP do not promote lipid oxidation in the raw filling mass, but result in higher MDA formation in cooked final products. The sensory panel found dry and rough consistence in 4% CP based cooked meat balls, while 2% CP enriched samples show nice sensory acceptance by the tasting committee. CP is suitable innovative ingredient for processing of value added cooked meat products.

CRICKET POWDER (ACHETA DOMESTICA) AS FOOD ADDITIVE FOR PROCESSING OF DRY-FERMENTED POLTURY BARS

In the recent years crickets, as well as cricket powder (CP) are interesting food ingredients in the European market. Some benefits of CP are high content of quality proteins, fats, vitamins and minerals and little environmental footprint. The aim of this work is to explore the impact of CP additive (2% and 4%) on the color characteristics, technological and sensory properties of dry-fermented poultry bars. The use of CP as meat additive significantly decrease L* and a* value of the product. Structural strength, plastic strength and pH were significantly increased (p˂0.05) in CP enriched raw and dry-fermented poultry bars. aW and moisture content in the final CP supplemented poultry products increased (p˂0.05). The incorporation of 2% CP had slight impact on sensory properties of final product and can be successfully used for processing of value added meat products. CP addition up to 4% had negative effect on the color, sensory properties, structural and plastic strength on the filling mass and dry-fermented meat bars.

Strength models of the terrestrial planets and implications for their lithospheric structure and evolution

Knowledge of lithospheric strength can help to understand the internal structure and evolution of the terrestrial planets, as surface topography and gravity fields are controlled mainly by deformational features within the lithosphere. Here, strength profiles of lithosphere were calculated for each planet using a recently updated flow law and taking into account the effect of water on lithospheric deformation. Strength is controlled predominantly by brittle deformation at shallow depths, whereas plastic deformation becomes dominant at greater depths through its sensitivity to temperature. Incorporation of Peierls creep, in which strain rate is exponentially dependent on stress, results in the weakening of plastic strength at higher stress levels, and the transition from brittle to ductile deformation shifts to shallower depths than those calculated using conventional power-law creep. Strength in both the brittle and ductile regimes is highly sensitive to the presence of water, with the overall strength of the lithosphere decreasing markedly under wet conditions. The markedly low frictional coefficient of clay minerals results in a further decrease in brittle strength and is attributed to expansion of the brittle field. As plastic strength is influenced by lithology, a large strength contrast can occur across the crust–mantle boundary if deformation is controlled by ductile deformation. Effective elastic thickness for the terrestrial planets calculated from the rheological models indicates its close dependence on spatiotemporal variations in temperature and the presence of water. Although application of the strength models to observed large-scale surface deformational features is subject to large extrapolation and uncertainties, I emphasize the different sensitivity of these features to temperature and water, meaning that quantifying these features (e.g., by data from orbiting satellites or rovers) should help to constrain the internal structure and evolution of the terrestrial planets.