KEY WORDS:

magnesium pyrophosphate, ceramics, struvite, newberyite

ABSTRACT

The phase composition of the powder synthesized from aqueous solutions of magnesium chloride MgCl₂ and ammonium hydrogen phosphate (NH₄)₂HPO₄ was represented by struvite MgNH₄PO₄^.6H₂O and newberyite MgHPO₄^.3H₂O. The synthesized powder with molar ratio Mg / P = 1 was used to use a ceramic material based on β-magnesium pyrophosphate β-Mg₂P₂O₇. The ceramic material after firing at 1100°C had a relative density of 33% (~1 г/см³). Porous ceramic biocompatible resorbable material based on β-magnesium pyrophosphate β-Mg₂P₂O₇, obtained from the synthesized powder, which was a mixture of struvite MgNH₄PO₄^.6H₂O and newberyite MgHPO₄^.3H₂O, can be used for creation of implants for temporarily compensation of bone tissue defects.

FOR CITATION: Kazakova G.K., Safronova T.V., Shevtsova O.A. Powder synthesized from magnesium chloride and ammonium hydrophosphate for preparation of ceramics based on magnesium pyrophosphate // Technique and technology of silicates. 2021.Vol. 28. No3. Pp 68 – 73 (rus)

KEY WORDS:
C-S-H cement phase, additives, pressing, Raman spectroscopy, composition of silicon-oxygen anions.

ABSTRACT

The effect of nano SiC additives with a particle size less than 50 nm, carbon black with a specific surface area of about 80 m²/g, SiO₂ and Al₂O₃ sols, AlCl₃, FeCl₃ solutions on the composition of silicon-oxygen anions in the pure C-S-H phase was studied. The mixture was pressed at a specific pressure of 100 MPa and tested for compressive strength after 1 hour, 4 and 10 days of normal aging. The Raman spectroscopy method was used to determine the composition of silicon-oxygen anions in the C-S-H phase and compared it with the strength of the stone.
It was found that the initial powder of the C-S-H phase mainly contains isolated Q⁰ and terminal Q¹ tetrahedra [SiO₄]. Pressing the powder at 100 MPa leads to the advanced formation of chains of crosslinking Q² and Q³ tetrahedra. The addition of silica to C-S-H promotes maximum chain formation from Q². The Raman spectrum of C-S-H with silica sol is identical to the spectrum of hydrated cement. Iron chloride prevents the formation of extended chains of silicon-oxygen tetrahedrons. Carbon-containing nano-additives significantly alter the spectrum of C-S-H calcium substructures.

FOR CITATION: Ovcharenko G. I. Influence of additives on the composition of C-S-H сement phase anions // Technique and technology of silicates. 2021. Vol. 28. No3. Pp 74 – 80 (rus)

KEY WORDS:
nanosized particles, stabilized suspensions, cement paste. cement matrix, structure formation

ABSTRACT

The use of nanosized particles in the production of building materials allows at the microlevel to control the processes occurring during the hardening of cement and purposefully manage the composition of hydrated neoplasms. Uniform distribution of nanoparticles is achieved by using aqueous suspensions of nanosized particles stabilized with a plasticizer. Nanosized particles of non-hydraulically active materials in a cement matrix cause forced crystallization of hydrated neoplasms that make up the structure of a cement stone. It was found that the degree of hydration of cements with suspensions of nanoparticles is 15-18% higher. The effectiveness of the use of nanosized particles in the structuring of cement pastes consists: by imparting mobility to the cement paste in the initial period of hydration, the possibility of plasticizing it without blocking the surface of cement particles with surfactants, and makes it possible to obtain dense and durable structures of the cement matrix with improved physical and mechanical characteristics. The porosity of cements with suspensions after 28 days of hardening is 20 - 35% lower than that of non-additive cement. And the strength of the samples after 24 hours increases 1.5 - 1.8 times.

FOR CITATION: Kozlova I.V. Experience of applying of nanosized particles in production of building materials // Technique and technology of silicates. 2021. Vol. 28. No3. Pp 81 – 87 (rus)

KEY WORDS:

Synthetic anhydrite, sulfate activator, alkaline activator, modified binder, filling mixture

ABSTRACT

The manufacture of building materials based on natural anhydrite does not imply any firing operations. That additionally contributes to an increase in consumer demand. However, under normal conditions, natural anhydrite slowly reacts with water, which requires the use of special-purpose additives - hardening activators. In this work, we studied the preparation of a modified anhydrite binder using complex alkaline and sulfate activators. And also the establishment of the composition and dispersion of the modified binder, which must meet the requirements for filling mixtures. It is shown that the combined use of portland cement and potassium sulfate as alkaline and sulfate activators is a modified additional component. And that they can directly affect the initial hardening time of synthetic anhydrite. The modified binder with a specific surface area of 450 m2 / kg, in combination with the additives, makes it possible to create a filling mixture with the required building characteristics. In the work, the optimal compositions of filling mixtures have been established, which correspond to both technological and physical and mechanical properties.

FOR CITATION: Buryanov A.F., Galtseva N.A., Buldyzhova E.N. Modified binder based on synthetic anhydrite // Technique and technology of silicates. 2021. Vol. 28. No3. Pp 88 – 94 (rus)

KEY WORDS:

dispersion, barium-containing additive, barium additive, barite cement, radiation-shielding building materials, properties of cement

ABSTRACT

Development of building materials science in creating reliable and effective radiation-protective building materials and products to ensure safe operating conditions for nuclear technologies is currently gaining special relevance. Barite-containing concretes are widely used as radiation-protective building materials, as well as dry building mixes containing barite. However, the use of barite in composition requires some optimization and research. The aim of this work is to study the effect of the dispersion of a barium-containing additive on the physical and mechanical properties of cement. The object of the study was a barite concentrate with a proportion of barium sulfate 90% and cement CEM I 42.5 (500 D0). The barite concentrate was crushed to specific surface area 310m2 / kg, 570m2 / kg and 830m2 / kg and added to the cement composition in the amount of 10, 20 and 30%. Based on the results of experimental studies, the amount and fineness of grinding of the barium-containing additive was determined. The results of the study show that with an increase in the amount of the additive, the water demand of the material increases and the setting time of the cement paste is lengthened. The density of the material increases with an increase in the content and fineness of grinding of the barite concentrate. The best strength characteristics are demonstrated by the material containing 20% of the additive by weight of the binder.

FOR CITATION: Samchenko S.V., Davidyuk A.N., Novikov N.V. Influence of dispersity of barium-containing additives for radiation-protective composite materials on physical and mechanical properties of cement // Technique and technology of silicates. 2021. Vol. 28. No3. Pp 95 – 100 (rus)

KEY WORDS:

modulus of elasticity, compressive and flexural strength, repair composition, fiber content, efficiency of dispersed reinforcement, fiber.

ABSTRACT

The influence of the chemical nature and volume content of fiber on the compressive and bending strength of repair compounds is considered. The high efficiency of the fiber obtained from a structured ferromagnetic micropipe is shown. The linear dependence of the tensile strength during bending of the dispersed-reinforced repair compound on the elastic modulus during stretching of the used fiber is revealed. It is proposed to evaluate the effectiveness of dispersed reinforcement of repair compounds by the ratio of the degree of increase in bending strength of repair compounds to the difference in elastic modulus under tension of the applied fiber (tga). A linear dependence of tga on the volume content of fiber in the repair composition has been established.

FOR CITATION: Ushkov V.A., Nalbandyan G.V., Zorin D.A., Kiryakova L.V. Strength of dispersed-reinforced repair compounds // Technique and technology of silicates. 2021. Vol. 28. No3. Pp 101 – 109 (rus)

KEY WORDS:

concrete strength, sulphate-resistant Portland cement, fly ash, calcination losses, microsilicon, quartz flour

ABSTRACT

The article considers the effect of substitution of a part of sulfate-resistant Portland cement in the composition of a multicomponent binder with low-calcium fly ash when used together with micro-silica, as well as partial replacement of fine aggregate with quartz flour obtained as a result of fine grinding of quartz sand on the workability of concrete mixtures and strength properties of concrete. Modern research methods corresponding to the current standards of the Russian Federation and the Socialist Republic of Vietnam were used. The influence of two types of fly ash of class F of the “Fa Lai” thermal power plant, differing in granulometric composition and losses during calcination, has been studied. The indicators of the workability of concrete mixtures of the developed compositions, as well as the compressive strength, axial tension and flexural tension of the concretes obtained as a result of their solidification are determined. It has been established that concrete mixtures and concretes containing more finely dispersed fly ash with a low value of losses during calcination (0.95% by weight) have better indicators compared to similar compositions with less dispersed ash in terms of component content, characterized by a higher value of such losses (5.74% by weight). The results obtained allow us to conclude that it is possible to replace up to 40% of the mass in the composition of a multicomponent binder sulphate-resistant Portland cement by 30% by weight fly ash in combination with 10% by weight of microsilicon while maintaining high strength of concrete at the 28-day age of hardening - compression 88.8-96.0 MPa, axial tension 6.06-6.43 MPa and flexural tension 9.24-9.51 MPa.

FOR CITATION: Nguyen Duc Vinh Quang, Aleksandrova O.V., Bulgakov B.I., Korovyakov V.F., Kaddo M.B. The effect of fly ash in a multicomponent binder on the strength of concrete // Technique and technology of silicates. 2021. Vol. 28. No3. Pp 110 – 116 (rus)

KEY WORDS:

chemical activation, silica, complex additive, alkaline medium, micro-reinforcing fiber, modification of the cement stone structure, hydrophysical properties.

ABSTRACT

Within the framework of the study, the authors considered the issues related to the activation of microsilicon, which is a waste of Ferroalloy production, and methods of its use for modifying the structure of cement stone, in particular, for heavy concrete. The mechanism of the structure formation, the method of introduction and the optimal consumption of the additive for modifying the concrete mix are determined. Using a comprehensive study, the dispersion products of microsilicon, which is a part of the complex modifier, were determined. It is established that the process of chemical activation of mineral particles has not been sufficiently studied, and therefore the presented research for finding solutions to improve performance through the process of pretreatment of microsilicon with an alkaline medium pH=10,2 together with the micro-reinforcing component, is relevant.

FOR CITATION: Tkach E.V., Korshunov A.V., Temirkanov R.I. Comprehensive study of modified concrete based on activated microsilicon // Technique and technology of silicates. 2021. Vol. 28. No3. Pp 117 – 126 (rus)

KEY WORDS:

conductive concrete, building soot, superplasticizer, homogenization, manufacturability.

ABSTRACT

The most important functional property of conductive concretes is their ability to resistive heating when connected to electricity. Modern directions of research in the field of obtaining conductive composites based on cement matrices are aimed at improving the rheological properties of conductive concrete mixes. It is important for improving the electrical and operational properties of products. This study presents the kinetic dependences of the grinding of a cement-based composite binder on its electrical resistivity. To create a conductive artificial stone based on a composite cement binder, the following components were used: portland cement PC 500 D0, polycarboxylate superplasticizer, construction soot (technical carbon P-803) as conductive material. The obtained values of electrical resistivity for the samples indicate an increase in electrical resistivity due to the transition of water into a bound state. The electrical resistivity for the samples varied from 70.2 Ω*m to 187.8 Ω*m. The results obtained allow us to conclude that there is no direct proportional relationship between the kinetics of homogenization and the electrical resistivity value.

FOR CITATION: Larsen O.A., Bahrakh A.M. Composite binder for conductive concrete // Technique and technology of silicates. 2021. Vol. 28. No3. Pp 127 – 131 (rus)