scholarly journals KINETICS OF RHEOLOGICAL CHARACTERISTICS OF FOAM CONCRETE MIXTURE

2021 ◽  
pp. 110-118
Author(s):  
V. Martynov ◽  
◽  
O. Martynova ◽  
V. Elkin ◽  
S. Makarova ◽  
...  
Keyword(s):  
Structural Strength ◽  
Solid Phase ◽  
Chemical Activation ◽  
Experimental Studies ◽  
Concrete Mixture ◽  
Rheological Characteristics ◽  
Foam Concrete ◽  
Plastic Strength ◽  
Kinetics Of ◽  
Cellular Concrete

Abstract. 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.

scholarly journals ETHOD FOR MANAGING THE STRUCTURAL-MECHANICAL PROPERTIES OF FOAM CONCRETE MIXTURES

2018 ◽  
Vol 45 (2) ◽  
pp. 183-190
Author(s):  
A. Yu. Bogatina ◽  
V. N. Morgun ◽  
L. V. Morgun
Keyword(s):  
Mechanical Properties ◽  
Solid Phase ◽  
Experimental Studies ◽  
Building Structures ◽  
Foam Concrete ◽  
State Register ◽  
Concrete Mixtures ◽  
Wall Structures ◽  
Plastic Strength ◽  
Scientific Ideas

Objectives At present, the urgency of scientific research aimed at reducing the material consumption of building structures is growing. Since foam concrete proved to be an effective material for wall structures, the aim of the present work was to develop scientific ideas about features of their macrostructural formation at the “viscous to solid” phase transition.Methods The evaluation of plastic strength was carried out according to the patent for invention No. 2316750 (“Method for determining the plastic strength of foam concrete mix” registered in the State Register of Inventions of the Russian Federation on February 10, 2008). Synthetic PO-3NP (TU 38-00-058079999-20-93) and "Arecom-4" galipot glue analogue (TU 31-10) were used as foam generation agents. Control over the kinetics of the plastic strength of the test mixtures of equal density was carried out in five-litre vessels at an interval of 15 minutes for three hours.Results The paper considers the most important features of mass transfer, which control the formation of defectiveness for interporal partitions in foam concrete. From the analysis of theoretical and experimental data, it follows that the ratio between water and surfactant consumption is an important tool for managing the quality of foam concrete mixes. Definingthe optimal relationship between water consumption and the amount of foaming agent allows the maximum amount of surfactants to be located at the gas-liquid interface ensuring minimal defect in the structure of the interporal partitions in the cured concrete.Conclusion The theoretical and experimental studies carried out make it possible to consider the relationship between the consumption of water and surfactant as an important tool for controlling the structural and mechanical properties in foam concrete mixes.

scholarly journals EFFECT OF POROUS STRUCTURE ON SOUND ABSORPTION OF CELLULAR CONCRETE

2020 ◽  
Vol 3 (2) ◽  
pp. 5-18 ◽  
Author(s):  
R.S. Fedyuk ◽  
A. Baranov ◽  
Y.H. Mugahed Amran
Keyword(s):  
Open Porosity ◽  
Sound Absorption ◽  
Concrete Mixture ◽  
Sound Waves ◽  
Foam Concrete ◽  
Mechanical Adhesion ◽  
The Matrix ◽  
Reduce Shear Stress ◽  
The Mathematical Model ◽  
Cellular Concrete

the compositions of gas and foam concrete with improved acoustic characteristics were developed. The optimal form of porosity, which contributes to the absorption of sound waves, both in the range of audible frequencies and at infrasonic and ultrasonic frequencies, is revealed. The mathematical model for designing sound-absorbing concrete was improved, taking into account both the porosity of the composite and the influence of the porous aggregate. The laws of synthesis of aerated concrete and foam concrete are established, which consist in optimizing the processes of structure formation due to the use of a polymineral cement-ash binder and blowing agent. The composition of the composite intensifies the process of hydration of the system, which leads to the synthesis of a polymineral heterodisperse matrix with an open porosity of more than 60%. Peculiarities of the influence of the “Portland cement – aluminosilicate – complex of modifiers” system on the rheology of the concrete mixture was identified, which can significantly reduce shear stress and create easily formed cellular concrete mixtures. The increased activity and granulometry of aluminosilicates predetermine an increase in the number of contacts and mechanical adhesion between particles during compaction, strengthening the frame of inter-pore septa. The mechanism of the influence of the composition of the concrete mixture on the microstructure of the composite is established. The presence of refined aluminosilicates and a complex of additives in the system along with cement contribute to the synthesis of the matrix with open porosity, thereby increasing the sound absorption coefficient.

Thermal Insulating and Constructive Foamed Concrete on a Composite Gypsum Binder

2019 ◽  
Vol 974 ◽  
pp. 125-130 ◽  
Author(s):  
Natalia V. Chernyisheva ◽  
Svetlana V. Shatalova ◽  
Maria Yu. Drebezgova ◽  
Evgeniy N. Lesnichenko
Keyword(s):  
Concrete Mixture ◽  
Foam Concrete ◽  
Thermal Insulating ◽  
Mineral Addition ◽  
Foamed Concrete ◽  
Stepwise Loading ◽  
Cellular Concrete ◽  
Loading Scheme

The article discusses the possibility of obtaining the effective thermal insulating and constructive foamed concrete on a composite gypsum binder. The composition was selected, the stepwise loading scheme of the foam concrete mixture components was proposed, the properties and microstructure of cellular concrete based on a composite gypsum binder with mineral addition of finely-dispersed concrete scrap were studied.

Impact of Superplasticizing Agents on Physical and Mechanical Properties of Cellular Concrete

2019 ◽  
Vol 974 ◽  
pp. 181-186
Author(s):  
V.A. Perfilov ◽  
V.V. Gabova ◽  
Inessa A. Tomareva
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
Pore Space ◽  
Experimental Studies ◽  
Basalt Fiber ◽  
Physical And Mechanical Properties ◽  
Foam Concrete ◽  
Cellular Concrete

The effect of superplasticizing, foam agents, various fiber aggregates on the physical and mechanical properties of cellular concrete has been studied. The article covers the results of experimental studies conducted to determine the effect of foam agents PO-6 and PB-2000, as well as polymeric and basalt fiber on the pore structure of foam concrete. The dependence between the change in density and strength of cellular concrete and the structure of its pore space has been determined.

Recent Studies of the Action of Inorganic Inhibitors

CORROSION ◽  
1962 ◽  
Vol 18 (9) ◽  
pp. 316t-322t ◽  
Author(s):  
G. H. CARTLEDGE
Keyword(s):  
Solid Phase ◽  
Experimental Studies ◽  
Anodic Process ◽  
Radioactive Tracers ◽  
Semiconductor Physics ◽  
Oxidation Reduction ◽  
Adsorption Of Gases ◽  
Electrostatic Polarization ◽  
Solute Species ◽  
Kinetics Of

Abstract The goal in recent studies of the action of inhibitors has been to apply some of the concepts and experimental techniques that have been fruitful in problems of electrode kinetics, heterogeneous catalysis and, to some extent, semiconductor physics. The purpose has been to determine fundamentally the manner in which an inhibitor of corrosion acts. In order to disclose the nature of the corrosion process to be inhibited, some of the recent work on the anodic process is discussed. The importance of adsorption and of semiconducting surfaces in the kinetics of electrode reactions is illustrated. The principal theories of inhibitor action are outlined and discussed in the light of recent experimental studies, in which radioactive tracers have had a prominent role. In considering the physical-chemical basis for the specificity of solute species as inhibitors, it is shown that such species may interact with a solid phase through a variety of mechanisms. These include oxidation-reduction processes, adsorption and ion-exchange, and electrostatic polarization. The effects of these interactions are shown to correlate with phenomena observed in the adsorption of gases on metals and in certain surface properties of semiconductors. The conclusion reached is that a comprehensive consideration of all such types of interaction is necessary for an understanding of the action of inhibitors. 5.8.3, 5.8.4, 3.2.2

scholarly journals Study of the kinetics of carboxymethyl cellulose synthesis in a screw reactor

2021 ◽  
Vol 6 (3(62)) ◽  
pp. 15-20
Author(s):  
Kateryna Konovalenko ◽  
Yurii Beznosyk ◽  
Liudmyla Bugaieva
Keyword(s):  
Carboxymethyl Cellulose ◽  
Solid Phase ◽  
Homogeneous Model ◽  
Experimental Studies ◽  
Heterogeneous Reactions ◽  
Process Conditions ◽  
Cellulose Synthesis ◽  
Important Indicator ◽  
Screw Reactor ◽  
Kinetics Of

The object of research is the reactor for the synthesis of carboxymethyl cellulose. An important indicator of the quality of sodium carboxymethyl cellulose, which determines the field of its application, is the degree of polymerization. However, obtaining a product with a specific parameter under industrial conditions is associated with a number of difficulties. Therefore, important research tasks are the development of a mathematical model of the kinetics of carboxymethyl cellulose synthesis, experimental studies to determine the rate constants of synthesis reactions, modeling of a screw reactor for the synthesis of carboxymethyl cellulose, and computer studies. When studying the kinetics of reactions of carboxymethyl cellulose, one of the possible approaches was to use a quasi-homogeneous model, which is widely used in modeling processes on a catalyst grain. This approach is used to describe and analyze individual stages; however, a number of difficulties arise in heterogeneous reactions of cellulose. In the course of these reactions, the properties of the solid phase change and the processes, respectively, are unsteady in time. The reaction does not take place on the surface of hard particles, but in the entire volume of the fibers. The concentration and reactivity of cellulose hydroxides, water, and products formed during the reaction remain approximately constant; therefore, the use of a quasi-homogeneous model is quite acceptable and does not cause additional mathematical difficulties. As a result of these experiments, according to the obtained integral curves, the method of least squares was used to find the constants. To determine the values of the kinetic constants, an experiment was carried out in an integral isothermal reactor. During the experiments, the degree of substitution of carboxymethyl cellulose and the concentration of free alkali were measured. As a result of numerous implementations of the search task, the values of the constants and activation energies were obtained. This kinetic modeling approach can be used in the synthesis of other cellulose ethers. The rate constant of the synthesis reaction depends on the process conditions. Using the proposed approach to describing the interaction of cellulose with a reagent, the reaction mixture considered as a quasi-homogeneous system can be described using a single-phase flow model.

scholarly journals Mechanochemical Activation Effect on Technogenic Iron Oxide Reduction Kinetics

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 320
Author(s):  
Oleg Sheshukov ◽  
Mikhail Mikheenkov ◽  
Larisa Vedmid ◽  
Denis Egiazaryan
Keyword(s):  
Iron Oxide ◽  
Reaction Kinetics ◽  
Iron Oxides ◽  
Mechanochemical Activation ◽  
Solid Phase ◽  
Experimental Studies ◽  
High Rate ◽  
Oxide Reduction ◽  
Iron Oxide Reduction ◽  
Kinetics Of

Understanding the reaction kinetics of iron oxide reduction by carbon is a key task of the theory of metallurgical processes. One of the understudied features of the reaction kinetics of iron oxide solid-phase reduction by carbon is the discrepancy between the reacting substances’ small contact area and the process’s high rate. A convincing theoretical and experimental explanation of this effect has not yet been obtained. The data obtained earlier show that an increase in the scale of the briquetting pressure from 0 to 300 MPa increases the degree of its metallization during heating two-fold, and the metallization temperature decreases by more than 40 °C. Therefore, it was assumed that these effects during heating are a consequence of the mechanochemical activation (MCA) of iron oxides in the scale during its pressing. This paper presents the results of experimental studies on the influence of two types of scale MCA (grinding and pressing) on iron oxide reduction. The study of the MCA effect on the reaction kinetics of scale iron oxide reduction by carbon is a promising way to assess the criteria for scale phase composition changes under external factors. The presented results indicate a decrease in the amount of trivalent iron oxide (Fe2O3) after the MCA and an increase in the amount of one-and-a-half oxide (Fe3O4) and bivalent iron oxide (FeO). The obtained experimental data show that the initial stage of iron oxide reduction, consisting in the transition from higher iron oxides to lower ones, is possible at room temperature without carbon presence.

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

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