Construction materials science. Рубрика в журнале - Nanotechnologies in Construction: A Scientific Internet-Journal

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Anti-icing coating based on silicone resin SILRES® MSE100

Anti-icing coating based on silicone resin SILRES® MSE100

Valentina I. Loganina, Svetlana N. Kislitsyna, Evgenia V.Tkach, Irina V. Stepina

Статья научная

Introduction. The study is aimed at obtaining an anti-icing coating for building structures by creating a hydrophobic surface layer, which is regulated by surface energy and surface topography. Materials and methods. Acrylic resins A-01 and DEGALAN®, high-chlorinated polyethylene resin HCPE and silicone resin SILRES® MSE 100 were used in the research. Aerosil R 972 nanoparticles were used as a filler. The anti-icing properties of the coating were evaluated by the contact angle of the water drop with the coating, the static and dynamic contact angle, the wetting hysteresis, and the adhesion of ice to the superhydrophobic surface. Results and discussions. We have found that coatings based on acrylic resins A-01, DEGALAN®, high chlorinated polyethylene resin HCPE and silicone resin SILRES® MSE100 20% concentration do not provide superhydrophobic properties. The superhydrophobic effect is retained by coatings based on SILRES® MSE100 silicone resin 5% and 10% concentration. The force of detachment of a drop from a coating based on SILRES® MSE100 silicone resin at a 10% concentration is 3 times less, which ensures an easier rolling of a water drop from the surface and its anti-icing properties. The amount of ice on an untreated surface is 0.59 kg/m2, and on a surface treated with a composition based on SILRES® MSE100 silicone resin, it is 0.15 kg/m2. Conclusions. An anti-icing coating composition based on SILRES® MSE100 silicone resin has been developed. The proposed composition forms a coating characterized by anti-icing properties that remain in operation.

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Application of polyvinyl chloride for nanocomposites (analysis and optimization of quality indicators)

Application of polyvinyl chloride for nanocomposites (analysis and optimization of quality indicators)

Yulia F. Kovalenko, Ekaterina A. Shulaeva, Nikolai S. Shulaev

Статья научная

Introduction. The application of nanocomposites in various industries has increased in recent years due to their unique properties and performance characteristics. Enhancing the quality performance of nanocomposites presents a formidable challenge, primarily attributable to the intricate interactions among their constituent elements. This paper presents an overview of the methods used to analyze and calculate the quality performance of nanocomposites using PVC as the base material. Methods and materials. To calculate technological parameters that are not directly measurable, we conducted a thorough analysis of literature sources related to the specific process under consideration. Through this analysis, we established appropriate relationships between empirical data in accordance with the fundamental principles of thermodynamics and mass transfer processes. In the course of the research, the method of neural networks was applied in order to describe the process of vinyl chloride polymerization carried out by suspension method. To solve this problem, a cascade network with forward propagation of the signal and backward propagation of the error was applied. Network composition: in the hidden layer – ten sigmoid neurons, in the output layer – two linear neurons. Results and Discussion. Throughout this research, it was observed that the heat flux during polymerization exhibits temporal variation, contingent upon the concentration level of the initiator. Further the dependencies obtained can be used in controlling the flow rate of refrigerant into the reactor cooling jacket, to ensure that the entire process is isothermal. It was found that by varying the stirrer speed, it is possible to change the particle size and hence the molecular weight distribution of polyvinyl chloride. The developed neural network was tested. The obtained results have minimal error and are close to the real values, from which we can conclude that the network is trained correctly and the dependence between the data is found. Conclusion. Dependencies linking physicochemical parameters of the technological process with the design features of the apparatus have been established. To maintain the quality of PVC, in particular the appropriate molecular weight distribution, a neural network (a cascade network with direct signal propagation and reverse error propagation, consisting of ten sigmoidal neurons in the hidden layer and two linear neurons in the output layer) was developed in MATLAB environment. The network was trained on a sample and tested on test values, which showed that the network predicts the outcome of the process with minimal tolerable error, with other parameters unchanged.

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Binder properties for zol-silicate paint

Binder properties for zol-silicate paint

Yulia A. Sokolova, Valentina I. Loganina

Статья научная

Introduction. The binder for sol-silicate paints is made on the basis of a polysilicate solution obtained on the basis of liquid glass and silicic acid sol. The technological process of creating a polysilicate binder is complex and it is not always possible to achieve the required characteristics. In this regard, the development of a polysilicate binder and the creation of a sol-silicate paint based on it are relevant. Materials and methods. Silicic acid sols Nanosil 20 and Nanosil 30 produced by PK Promsteklotsentr were used in the work. We used sodium liquid glass with a modulus of M = 2.78, potassium liquid glass with a modulus of M = 3.29 (GOST 13078). The conditional viscosity of paints and varnishes was determined using a VZ-4 viscometer according to GOST 8420-74. “Paint materials. Methods for determining the conditional viscosity. Tensile strength (cohesive strength) was determined according to GOST 18299-72* “Paint and varnish materials. Method for determination of tensile strength, elongation at break and modulus of elasticity” on the tensile testing machine IR 5057-50. The silicate modulus of liquid glass was determined according to the method described in GOST 13078-81. The molybdate method was used to study the composition of liquid glasses and polysilicate solutions. Results and discussions. It was revealed that liquid glass and polysilicate solution are typical pseudoplastic bodies. The addition of a sol (an increase in the silicate modulus) promotes an increase in the proportion of high-polymer fractions of siliconoxygen anions (SCA), and with an increase in the sol content, the proportion of the polymeric form of silica increases. It has been established that there is a correlation between the content of silica in the polymer form and the tensile strength of the films, which means that with an increase in the content of silica in the polymer form, an increase in the tensile strength of the films is observed. Conclusions. It has been established that with an increase in the amount of silicic acid sol introduced, a decrease in the pH of solutions is observed at a constant alkali concentration. The introduction of a sol of silicic acid leads to a change in the viscosity of the solutions. The introduction of a sol of silicic acid into liquid glass promotes an increase in the proportion of high-polymer fractions of silicon-oxygen anions. Films based on polysilicate solutions are characterized by faster curing and higher tensile strength compared to films based on liquid glasses.

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Controlling the structural formation of porized cement composites in the production of thermally efficient enclosure structures of enhanced quality

Controlling the structural formation of porized cement composites in the production of thermally efficient enclosure structures of enhanced quality

Aleksei B. Steshenko, Aleksander I. Kudyakov, Aleksandr S. Inozemtcev, Sergei S. Inozemtcev

Статья научная

Introduction. Research to improve the quality of foam concrete products through targeted control of technological processes of structure formation of cement-based compositions is relevant. The strength of foam concrete is significantly influenced by the adhesion strength of the hardened cement paste to the aggregate. This article discusses methods of chemical and mechanochemical activation of foam concrete filler with glyoxal-containing additives, interaction with hydration products of binders and increasing the strength of the contact zone. The quality of foam concrete can be improved by controlling the properties of the contact zone. Materials and methods. The study was conducted using standard test procedures specified in national standards. Results. With preliminary chemical and mechano-chemical exposure of the sand surface to glyoxal-containing additives and its subsequent introduction into the foam concrete mixture the grade of strength of foam concrete increases to B1 while maintaining the average density grade D500 in comparison with foam concrete of the control composition, while the shrinkage value decreases by 20–38.5% and thermal conductivity coefficient by 37%. Conclusion. The use of glyoxal-based additives in foam concrete mixtures by pre-activating the sand surface can improve the quality of cement foam concrete.

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Exploring the Surface Chemistry for the Stabilization of Bismuth Titanate Fine Particle Suspensions in Cement Systems

Exploring the Surface Chemistry for the Stabilization of Bismuth Titanate Fine Particle Suspensions in Cement Systems

Svetlana V. Samchenko, Irina V. Kozlova, Olga V. Zemskova, Marina O. Dudareva

Статья научная

Introduction. The evolution of the construction industry in its current stage calls for the alteration of traditional building materials through the incorporation of nano- and fine-dispersed additives. These additions confer new, unique attributes to cement-based construction materials, enabling control over structure formation processes. Consequently, this allows for the creation of materials with specifically defined characteristics. Additives can be introduced into the cement composite during the joint grinding with clinker minerals, as a component of dry building mixture, or in the form of a suspension instead of mixing water. Therefore, it is essential to obtain fine particles suspensions resistant to aggregation and sedimentation. Thus, the purpose of this study is to obtain stabilized suspensions of bismuth titanate fine particles for cement systems and to study the properties of modified cement stone. Materials and methods. The purpose of this work was to establish the optimal concentration of polycarboxylate plasticizer in industrial water, necessary for the stabilization of fine bismuth titanate suspensions using surface tension and conductometric determination methods, the sedimentation stability of the obtained suspensions and the effect of ultrasonic exposure, as well as the physical and mechanical characteristics of cement stone modified with the obtained suspensions. Results and discussion. In order to establish the optimal concentration of the plasticizer necessary to obtain stable suspensions of bismuth titanate particles, the critical micelle concentration (CMC) for the plasticizer was determined with tap water as the dispersed medium. The CMC value was 1.3 g/l. If the concentration exceeds CMC, the process of micelle formation begins. In the micellar form, the plasticizer no longer provides stabilizing effect on the additive particles, therefore, the concentration of the plasticizer should be lower than the CMC. It was also found that ultrasound exposure increases the sedimentation stability of suspensions. The resulting stabilized suspensions were used instead of mixing water to obtain modified cement stone samples. There is an increase in the compressive strength of cement stone samples obtained after the introduction of fine bismuth titanate into the cement composite in the form of water suspensions stabilized by ultrasonic treatment with concentrations of 10, 30 and 50 g/l. The increase in compressive strength of modified samples compared to reference sample was from 24 to 33 MPa at first day age (by 13, 25 and 38% respectively), and from 80 to 93 MPa at 28 days age (by 4, 9 and 16%). Compressive strength of samples modified with bismuth titanate suspensions after ultrasonication compared to reference sample with plasticizer increased mostly at the first and third days age: from 29 to 42 MPa (by 31, 38 and 45%) and from 53 to 70 MPa (by 28, 30 and 32%) respectively. Conclusion. As a result of the research carried out in this study, the Critical Micelle Concentration (CMC) of a polycarboxylate plasticizer was determined, optimal for stabilizing fine-dispersed additive of bismuth titanate for cement systems, the effectiveness of ultrasonic treatment to achieve sedimentation stability of the obtained suspensions of the additive was confirmed, an increase in the strength characteristics of modified cement stone samples was established both in the initial hardening periods and at 28 days age. The results allow to consider a cement composite with fine bismuth titanate as a basis for obtaining building materials of new generation.

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Formation of porous structures in production technology of construction materials based on building gypsum plaster

Formation of porous structures in production technology of construction materials based on building gypsum plaster

Anna I. Kurmangalieva, Lyubov A. Anikanova, Aleksander I. Kudyakov, Aleksey B. Steshenko, Aleksander F. Buryanov, Nadezhda A. Lukyanova, Aleksander S. Inozemtsev, Segey S. Inozemtsev

Статья научная

Introduction. This article presents the results of the research works on formation of building gypsum plaster porous structure with the use of recovered anhydrite raw materials and chemical additives, and describes a method for production of wall materials. The relevance of this paper is stipulated by the need to expand the range and increase the manufacture of heat-insulating and structural-heat-insulating products based on gypsum binders and local mineral raw materials, as well as the development of technologies to ensure the production of gypsum materials with improved performance. The authors proposed certain methods for forming the porous structure of building gypsum plaster and improving its performance in terms of porosity and thermal conductivity through the use of modified recovered raw materials and chemical additives of calcium chloride and sodium carbonate. Materials and methods. The study of the effect of modifying additives on the properties of the mixture was carried out using gypsum paste of normal consistency (NC = 55%). The preparation of samples and testing were performed according to the methods specified in the national standards with the use of porous additives of calcium carbonate, fluoroanhydrite and chemical additives for the rheological properties of the mixture, average density and strength of the samples, the patterns and mechanism of the processes of gypsum stone structure formation were established. Results. The application of fluoroanhydrite modified in the disintegrator with an equimolar amount of calcium carbonate leads to a decrease in the average density of the samples to 40% with evenly distributed pores. The analysis of the microstructure of heat-insulating material samples with a density of 550 kg/m3 showed that the average diameter of micropores is 0.45 mm, while the thermal conductivity of samples with complex chemical additives has the thermal conductivity coefficient of 0.25 W/m°C, which is 30% lower than the thermal conductivity of samples without complex additives. Conclusions. The results obtained create the basis for using recovery raw materials and domestic modifying additives as a pore-forming agent, which allow regulating the structure of gypsum stone in order to produce effective wall materials.

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High-Performance Concretes for Machine Building with Nano- and Micro-Scale Raw Materials

High-Performance Concretes for Machine Building with Nano- and Micro-Scale Raw Materials

Vitaly A. Beregovoy, Evgeny V. Snadin, Alexander S. Inozemtsev, Anton S. Pilipenko

Статья научная

Introduction. The unique combination of rheotechnological properties and mechanical performance opens up prospects for the application of self-compacting and high-strength concretes in the manufacturing of base elements for machines and industrial equipment. The processes of adsorption of modern plasticizers on various mineral and polymeric modifiers of concrete mixtures were investigated. The compatibility of nano- and micro-scale mineral additives in composite cementitious binders was determined using calorimetry with an improved semi-adiabatic setup. Materials and methods. The cementitious binders used were CEM 52.5N Portland cement (Asia Cement LLC, Russia) and Nanodur (Germany, Dyckerhoff GmbH); hyperplasticizers included Melflux 1641F, 2651F, 5581F (Germany), PCE TR-6088 (China), Sika ViscoCrete 240 HE Plus and 226-P (Russia); superabsorbent polymer; nano- and micro-scale mineral additives included microsilica MK-85, metacaolin VMK-45, microcalcite MM-315, marshalite Silverbond 15 EW, and ground silica-containing rocks. Selective dissolution, differential thermal analysis, laser granulometry, and semi-adiabatic calorimetry were employed. Results and discussion. The quality of ultrafine mineral additives determines their ability to chemically bind portlandite through pozzolanic activity. Among the investigated additives, microsilica and gaize demonstrated the highest pozzolanic activity. Thermal activation was effective for components consisting of crystalline silica (marshalite, ground quartz sand), resulting in a 25% increase in performance. There was no selective adsorption of hyper plasticizer molecules by superabsorbent modifiers based on sodium polyacrylate compositions. Metakaolin and tremolite exhibited high adsorption to hyper plasticizers among the mineral additives. The rapid evaluation of the influence of formulation factors on the setting of cementitious composites was tested on an improved version of the semi-adiabatic calorimeter. Conclusions. The presence of micro-scale mineral additives based on microsilica in composite cementitious binders enables the development of high-performance concretes adapted for machine building. The study of pozzolanic activity, adsorption capacity, and cumulative heat release curves has indicated the feasibility of replacing microsilica with metacaolin and the potential for its partial blending with finely ground natural gaize. Analysis of the thermal effects accompanying the hydration processes of the "cement-additive-water" system with calorimeters allows us to provide more efficient research on the compatibility of additives in high-performance concrete compositions.

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Investigation of the process of moisture crystallization in bricks

Investigation of the process of moisture crystallization in bricks

Zheldakov D.Yu., Kozlov V.V., Kuznetsov D.V., Sinitsin D.A.

Статья научная

To solve the problems concerning moisture behaviour in the material of construction’s enclosure, especially at alternating temperatures, is very important for the correct calculations of resistance to heat conduction of construction’s enclosure and, ultimately, for comfortable living conditions. However, there are still no methods for building enclosure’s materials that could determine the temperature of moisture crystallization in the material in solid phase. The premise of the research is that water incoming to the material of construction’s enclosure, presenting in the construction’s material in the form of oxides and salts, as a result of hydrolysis process of some elements, is an eutectic solution with unstable composition and concentration. Thus, the research of moisture crystallization process transfers from micro- area (when determining the temperature of crystallization by the size of material’s pores) to the nano- area when researching the eutectic solution at the possible condition of hydrates formation. The experimental technique was developed to perform laboratory research of the process of moisture freezing. The technique takes into account that freeze-thaw process of moisture in solid body is studied at significant difference between mass of liquid phase and mass of solid phase. The method was simplified for the broad use at working conditions. The simplicity of the method aimed at obtaining experimental resultsis compensated by the developed mathematical method of processing the results of the research. Mathematical solution of the problem based on the comparison of freezing curves behaviour of the samples in dry and humidified samples. Apart from the temperature of moisture freezing, the developed method allowed obtaining additional characteristics of moisture states, such as amount of unfrozen moisture in construction’s material, supercooling temperature, heat capacity of moisture in liquid and solid states, concentration of dissolved agents. Knowing the concentration of dissolved agents in the material, even without knowing the exact composition of these agents, allows manipulating the temperature of moisture freezing at the nanotechnology level.

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Justification of the criteria requirements for fillers in mixtures for 3D construction printing

Justification of the criteria requirements for fillers in mixtures for 3D construction printing

Galina S. Slavcheva, Igor O. Razov, Valentina A. Solonina, Yulia F. Panchenko

Статья научная

Introduction. As part of the task to create new materials for additive technologies, an analysis of the situation was carried out, and a problem was identified with the lack of common approaches to selecting raw material components for mixtures. Theoretical concept. Based on the approaches of fundamental structure rheology, physicochemical mechanics of disperse systems, the theory of packing of granular media, we theoretically justified the criteria requirements for the characteristics of fillers and suggested quantitative criteria for their evaluation. It was proposed to use these quantitative criteria for a preliminary comprehensive assessment of fillers when designing compositions of mixtures for 3D construction printing. Materials and methods. The characteristics of the fillers were evaluated using scanning electron microscopy with a scanning electron microscope Thermo Scientific™ Phenom™ Desktop SEM and processing of images by the ParticleMetric software package as well as using laser granulometry with a laser analyser of particles Analysette 22. Results. We assessed the cement and 5 types of fillers that had different sizes and played different roles in the formation of the mixture properties. We also identified their estimated criterial characteristics, including the average particle diameter, gra-nulometric constant, and particle shape coefficient. Boundary values of these characteristics were determined for particles of different morphology and dispersion degree. Conclusion. Based on the application of the suggested theoretical approaches, we determined the lines of research associated with obtaining experimental patterns of the impact of the criterial characteristics of fillers on the rheological characteristics of mixtures as well as with these characteristics according to their significance and justifying the requirements for the range of quantities of fillers depending on their size, shape, and granulometry.

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Lime-diatomic mortar for finishing the walls of buildings

Lime-diatomic mortar for finishing the walls of buildings

Loganina V.I.

Статья научная

Introduction. At present, when performing finishing and restoration work, more and more preference is given to dry lime mixes (DBM). Wide opportunities for the production of dry lime-cement mixes are opened up by the use of diatomite, which is both a dry mix filler and an active mineral additive. Previous studies have confirmed the effectiveness of heat treatment of diatomite. After firing at 600–800оC, activity increases when interacting with calcium oxide hydrate. This is explained by the fact that at 600–800оC clay substances are dehydrated to metakaolinite, which is characterized by increased reactivity. The properties of dry mixtures and compositions based on them are affected by the particle size of the components of the dry mixture. In this regard, it is of great importance to study the influence of the dispersion of the components of the dry mixture on the formation of the structure of the finishing compositions. Materials and methods. To study the active centers of the diatomite surface, we used the indicator method for determining the distribution of adsorption centers. Determination of the compressive strength was carried out on a DOSM-3-1 dynamometer on samples 3x3x3 cm in size at the age of 28 days of air-dry hardening of the compositions. The determination of the granulometric composition of the components of the dry mixture was carried out by the method of sedimentation analysis. Adsorption was estimated from the optical density measured with a PEC photoelectrocalorimeter. To study adsorption at the “liquid-solid” interface, the initial components of the dry mixture, lime and diatomite, were used. Results and discussions. Accordingto the data obtained, it was found that a particle size reduction of the dry mixture filler leads to an increase in the strength characteristics of lime-diatomite compositions.It was found that the introduction of C-3 additive into the water favorsincreasing dispersion of hydrated lime, improving plasticity finishing mixture and improving the physical and mechanical characteristics lime-diatomaceous compositions.It is proposed to introduce sulfate additiveinto the formulation of the aluminumdry mixture. Increase in the compressive strength of the finishing composition with addition of aluminum sulfate 1.5–2 times was observed. Conclusion. It has been determined that the developed dry mixture is highly competitive, in terms of technological and operational properties,withprototype. Moreover, the production of the proposed DBM is more economical due to the use of local raw materials and domestic additives.

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Materials based on modified gypsum for facade systems

Materials based on modified gypsum for facade systems

Zhukov A.D., Bessonov I.V., Bobrova E.Yu., Gorbunova E.A., Demissie B.A.

Статья научная

Introduction. The use of gypsum in construction systems exposed to atmospheric influences involves the introduction of modifying additives of various types: polymer compositions, mineral fine and nanodisperse components, which can also be products of other industries. Methods and materials. To increase the weather resistance of gypsum stone, its strength characteristics and water resistance, the research considered a complex method of modifying gypsum binder by introducing aqueous solutions of polycondensation resins that harden in the material and nanocomponents. The experiment to assess the effect of the composition of complexly modified gypsum on its properties was carried out on the basis of the matrix of a complete quadratic three-factor experiment. Results. The strength of a complex modified gypsum stone during compression and bending increases by 30% and 25%, respectively, during 80 days of storage in the air. The compressive strength is 60 MPa, and the bending strength is 12 MPa. The samples can withstand 150 cycles of alternating freezing and thawing. Discussion. The introduction of polymer additives into the composition of the gypsum mixture leads to the fact that the gypsum during hydration creates a framework of crystalline aggregates of dehydrate, and the resin, when cured, forms a continuous polymer matrix. The polymer gypsum has the property of increasing the strength over time due to the ongoing polymerization of the resin. Conclusion. A weather-resistant gypsum-containing material was obtained. The use of man-made waste makes it possible to solve the problem of their disposal, which determines the reduction of the negative load on the environment. The methodology for assessing the weather resistance of gypsum stone, and, first, frost resistance, was tested.

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Mathematical modeling of physical and chemical processes in porous media in solving the problems of nanocomposite materials and water-filling

Mathematical modeling of physical and chemical processes in porous media in solving the problems of nanocomposite materials and water-filling

Valentina V. Kuzina, Svetlana V. Samchenko, Irina V. Kozlova, Alexander N. Koshev

Статья научная

Introduction. The complexity and laboriousness of system studies of physical and chemical processes in the volume and at the interface of the porous medium determines the need to apply mathematical modeling. This allows not only to identify and study the determining physical and chemical processes in a porous medium, but also to solve the problems of optimization and optimal control of processes and regimes by selecting the most favorable conditions. Methods and Materials. The method of mathematical modeling is used to study the processes, including the creation of composite and nanocomposite materials, as well as the moistening and moisture absorption in porous materials. In this context, the porous material is treated as a pseudohomogeneous medium with averaged physical and technological parameters. Results. The mathematical models of physical and chemical processes in the porous medium have been developed, the boundary conditions have been formulated, physical and effective constants have been determined. The processes in porous medium during metallization of carbon-graphite fibrous material, moistening of compacted textile material by an air flow, and moisture absorption by porous construction materials have been studied. Discussion. The adequacy of mathematical models to real physical and chemical processes is discussed. The results of calculations obtained by modeling equations implemented in the form of computer computational algorithms and experiments are compared. Conclusions. The effectiveness of the method for studying physical-chemical processes in a porous medium and for calculating optimal values of technological parameters has been established. ACKNOWLEDGEMENTS. The research was carried out with the financial support of Moscow State University of Civil Engineering. (Contract No. PSUAC/K-23 dated 05.06.2023) within the 2023 competition for basic and applied research (R&D) by scientific teams of organizations – members and strategic partners of the Industry Consortium “Construction and Architecture” in order to implement the Development Program of Moscow State University of Civil Engineering and Architecture for 2021–2030 as part of the Strategic Academic Leadership the “Priority-2030”.

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Nanomodification of cement-based composites in the technological life cycle

Nanomodification of cement-based composites in the technological life cycle

E.M. Chernishov, O.V. Artamonova, G.S. Slavcheva

Статья научная

The paper reviews the theoretical framework of nanomodification principles of building composites and the conceptual model of the nanomodification from the point of view of the evolutionary model of the solid phase formation depending on the kinetics of heterogeneous processes. According to the route, the main factors of the cement system nanomodifcation were identified for all stages of the technological life cycle. These are associated with the nano-sized particles playing the role of a) structure-forming nuclei, b) substrates for crystallization, c) centers of new formation zoning in the matrix substance of the material, d) nano-reinforcing matrix element. The concepts of the nanomodification and technological tools of the nanomodification of building composites are substantiated. Their hydration kinetics, phase composition, microstructure, rheology and strength characteristics are investigated in order to evaluate the efficiency of the nanomodification principles. It is shown that the use of the nanomodifiers enhances the ductility of cement paste, accelerates cement hydration processes by 9–28 times, and increases strength by 1.5–2 times. This will reduce the cost of flow, casting and hardening processes in the technological life cycle of cement-based composites.

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Patterns of structure formation in lime composites with additive based on amorphous aluminosilicates

Patterns of structure formation in lime composites with additive based on amorphous aluminosilicates

Kristina V. Zhegera, Anton D. Ryzhov, Julia A. Sokolova, Nikolay I. Shestakov

Статья научная

Introduction. One of the reasons for coating destruction enclosing structures is the formation of condensate at the boundary of the fence and the finishing layer. As a result of external impact and freezing of moisture in the pores of the plaster coating, a network of small cracks is formed, and it is also possible to peel off the finishing layer. To test this hypothesis, the facades of three different buildings were examined. It is established that all the studied plaster coatings are made on the basis of cement mortar. It is also known that lime mixture is used less often due to the lack of sufficient resistance to moisture. Therefore, there is a need to increase the resistance of coatings based on lime compositions. This can be achieved by introducing an alumosilicate-based modifying additive into it. Materials and methods. Liquid sodium glass, aluminum powder PAP-1 and distilled water were used for the synthesis of the additive. Slaked lime (pushonka) with an activity of 84% was used to prepare test samples. Fritsch particle sizer Analysette 22 was used to analyze the granulometric composition of the additive. Compressive strength was determined on the samples measuring 20×20×20 mm. A testing machine of the type “IR 5057-50” was used for the study of compressive strength of samples. The analysis of rheological properties was determined by the Shvedov-Bingham equation. To study the plastic strength (ultimate shear stress) of the finishing mixture, a conical plastometer KP-3 was used. The plastic viscosity of the composition was determined with a rotary viscometer BCH – 3. Results and discussions. The synthesized additive is a light powder of light gray color with a bulk density of 0.55 ± 0.05 g/cm3. The synthesized additive revealed a high content of oxides Al2O3, SiO2, Na2O respectively, amounting to 51.03%, 36.36%, 11.89%. The additive consists of particles of 100.0–200.0 microns, which make up more than 20% of the total composition. The influence of an aluminosilicate additive on a lime binder on rheological properties was investigated, a slight increase in static shear stress was revealed, respectively, an increase in the percentage of the additive. The value of the dynamic shear stress increases significantly with an additive content of more than 10%. Conclusions. The regularities of hardening of a lime binder with a nanostructured additive based on amorphous aluminosilicates are established, and the optimal content of an aluminosilicate additive in the amount of 10% by weight of lime is determined.

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Properties of Nano Engineered Concrete Subjected to Accelerated Corrosion

Properties of Nano Engineered Concrete Subjected to Accelerated Corrosion

A. Maher El-Tair, M.S. El-Feky, Alaa Mohsen, M. Kohail

Статья научная

Introduction. Many research had worked on improving the performance of concrete subjected to severe environment and improve concrete corrosion resistance. Using nano-materials is one of the methods had been used recently to improve concrete properties. In this research, a comparison between the performance of nano-silica and nano-clay in enhancing the durability properties of concrete was investigated. Methods and Materials. The experimental program was carried out through examining water absorption, water permeability, rapid chloride penetration test, corrosion resistance, bond strength of steel rebar before and after subjected to corrosion, and finally microstructure test. Nano-silica and nano-clay were added at 1%, 3%, and 5% as a partial replacement by weight of cement. Results. Both nano-silica and nano-clay showed significant performance in reducing the permeability and porosity of concrete and improve corrosion resistance of concrete. For comparison, nano-clay had a significant impact than that of nano-silica on concrete properties; in which the water permeability resistance of nano-clay mixes was enhanced by 87% than that of the control mix, while for nano-silica, it was 51% only. The chloride ion penetration was reduced by 72% for nanoclay mixes, while in nano-silica was 28%. Discussion. Nano-clay had a significant effect than that of nano-silica on the concrete durability properties; the flat-shaped of nano-clay particles had improved the microstructure of the cement matrix through the damping effect, besides the filling effect through the microstructure of the matrix which reduces the chloride ion penetration and improves water absorption and permeability of concrete. Conclusion. The optimum percentage of nano-silica is 1% by weight of cement as a partial replacement of cement by weight. However, for nano-clay is 5%, which gives the best performance in improve the durability properties of concrete.

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Research and optimization of the technology for the synthesis of a modifying additive based on a mixture of hydrosilicates and calcium aluminosilicates

Research and optimization of the technology for the synthesis of a modifying additive based on a mixture of hydrosilicates and calcium aluminosilicates

Loganina V.I., Frolov M.V.

Статья научная

Introduction. To improve the performance properties of lime coatings, modifying additives are introduced into their formulation. The development of a technology for the synthesis of an additive containing calcium hydro- and aluminosilicates, which promote the binding of lime and increase the resistance of the lime composite, is of current interest. Materials and methods. To prepare an additive based on a mixture of hydro silicates and calcium aluminosilicates, liquid sodium glass (GOST 13078), technical (purified) aluminum sulfate (GOST 12966), and quicklime were used. The pozzolanic activity of the materials was determined by the absorption of lime from lime mortar. Results. It has been established that the mineralogical composition of the additive obtained at the 1st stage of synthesis is represented by hydro silicates of the tobermorite group. The mineralogical composition of the additive obtained at the 2nd stage of synthesis is represented by hydro silicates of the tobermorite group, gypsum, and calcium aluminosilicates. The particle size of the additive is from 10 to 40 μm. The pozzolanic activity of the additive obtained at the first stage of synthesis was 238.6 mg/g, and that obtained at the second stage of synthesis was 3.2 times higher and amounted to 762.5 mg/g. The introduction of an additive obtained at the 2nd stage of synthesis into the composition increases the compressive strength of lime composites by 2.87 times. Conclusion. It is proposed to use a modifying additive obtained by a two-stage synthesis technology in heat-insulating DBM. The optimal concentration of the proposed modifying additive is selected, which is 10% by weight of lime.

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Structural and heat-insulating cement-based concrete with complex glyoxal based additive

Structural and heat-insulating cement-based concrete with complex glyoxal based additive

Aleksei B. Steshenko, Anna S. Simakova, Alexandr S. Inozemtcev, Sergei S. Inozemtcev

Статья научная

Introduction. The article presents the results of studies of the effect of complex additive based on glyoxal on the properties of cement-based foam concrete mix and foam concrete of natural hardening. The relevance of the study is determined by the necessity to provide the required process parameters of mixture for transportation and laying the formwork, as well as providing strength and thermal and physical characteristics of wall structures for the development of the northern regions of Russia, including the Arctic zone. It has been proposed to decrease the shrinkage deformations of the concrete mix and increase compressive strength of hardened foam concrete by affecting the cement matrix with complex modifier based on glyoxal. Materials and methods. The effect of modifying additives on the properties of the foam concrete mixture and foam concrete was studied at a W/S mixture ratio of 0.45. Research has been carried out using test methods set out in national standards. The results of the study of the effect of complex modifying additives (CMA) based on an aqueous solution of glyoxal and organic acids on the rheological and strength properties of foam concrete are presented, the regularities of the processes and the mechanism of structure formation of the modified foam concrete are determined. Results. The use of modifying additives leads to increase result in increasing the aggregative stability and reducing the plastic shrinkage of the foam concrete mix by 22–70%. In foam concrete with the complex additive LA 0.5% + Gl 0.55% the compressive strength rises from 1.96 to 2.43 MPa at the age of 28 days while maintaining the average density of D600. The thermal conductivity coefficient of foam concrete modified with various additives decreased by 5–30% compared to references. Conclusions. The obtained results of the study create in the construction industry the basis for the import substitution of modifying additives on the domestic mineral resource base and the production of effective structural and heatinsulating concretes for the development of the northern regions of Russia.

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Study of the kinetics structure formation of cement dispersed systems. Part I

Study of the kinetics structure formation of cement dispersed systems. Part I

Korolev E.V., Grishina A.N., Inozemtcev A.S., Ayzenshtadt A.M.

Статья научная

Introduction. The study of the kinetics structure formation is rarely the subject of a careful study. Although it is important for materials used to create elements of building structures, energy elements, thermoelements and materials for other purposes. The article proposes refinements of the methodology for determining the parameters of the kinetics structure formation of cement composites, including modified compositions. Methods and materials. The structure formation of cement systems with plasticizers, microsized mineral additives (hydrosilicates of barium, copper and zinc) and nanosized particles of zinc hydrosilicates has been studied. Results and discussion. It is proposed to single out two stages of initial structure formation: the stage of setting the cement paste and the stage of hardening. The selection of the setting stage is connected with the natural laws of the development of natural systems, namely, the initial formation of a structural grid obeys an exponential law. Moment of time when a deviation from this law is observed is the time of occurrence of spatial and/or prescription difficulties that hinder the exponential development of the system. Conclusions. A strong negative relationship between the parameters φ and β of the equation H(t) = a exp(φt β) has been established. These parameters characterize the rate of structure formation at the setting stage (parameter φ) and the density of the structure (parameter β or the internal dimension Di, 0 associated with it). The presence of such a negative relationship indicates the inadvisability of accelerating the processes of structure formation at the stage of setting. This is supported by a strong positive relationship between the period of initial structure formation t0, s1 and the strength of the material R28.

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Study of the kinetics structure formation of cement dispersed systems. Part II

Study of the kinetics structure formation of cement dispersed systems. Part II

Evgenij V. Korolev, Anna N. Grishina, Aleksandr S. Inozemtcev, Arkady M. Ayzenshtadt

Статья научная

Introduction. The study of the kinetics structure formation is rarely the subject of a careful study. Although it is important for materials used to create elements of building structures, energy elements, thermoelements and materials for other purposes. The article proposes refinements of the methodology for determining the parameters of the kinetics structure formation of cement composites, including modified compositions. Methods and materials. The structure formation of cement systems with plasticizers, microsized mineral additives (hydrosilicates of barium, copper, iron and zinc) and nanosized particles of zinc hydrosilicates has been studied. Results and discussion. It is proposed to single out two stages of initial structure formation: the stage of setting the cement paste and the stage of hardening. It was found that the strength of the material at the stage of hardening should be influenced by an additional factor, depending on the type of the introduced substance. A strong negative relationship between the parameters α and n of the equation R(t) = Rmax(1–eatn) at the hardening stage was confirmed. The trends identified at the setting stage also demonstrated, namely: an increase in the rate of structure formation leading to the formation of a less dense structure. Conclusions. An analysis of the change in the value of the internal dimension of the system during the transition from the stage of setting to the stage of hardening made it possible to identify two trajectories of the system development. The first trajectory appears only by combining the elements of the structure (trajectory No. 1). Preservation of the characteristic dimensions of structural elements, but an increase in the proportion of elements with small dimensions (when the conditions that prevent the combination of elements of the structure are realized) describes the second trajectory (trajectory No. 2). The implementation of trajectory No. 2 is typical for compositions which the structure formation of cement stone is carried out in the presence of Melment F15G plasticizer or microsized particles of copper or zinc. For other studied compositions, structure formation is proceeding with the enlargement of structural elements.

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