KEY WORDS:
cold weather concreting; self-compacting fine-grained concrete mix; "cold" concrete; automated monitoring; construction quality

ABSTRACT:

Accelerating the pace of construction is always an urgent task. When assembling housing construction, butt and plug joints must be monolithic with a concrete mixture that quickly gains strength. The task becomes more difficult when the construction of objects takes place at negative temperatures. There are many brands offering high-strength winter compositions on the market of dry building mixtures. In this work, dry building mixtures of B50 and B60 compressive strength classes were used. The quality control of the sealing of plug connections was carried out in 2 stages. The strength control of the solution was carried out in a testing laboratory, the compressive strength was determined on samples-cubes 40×40×40 mm, 70×70×70 mm and 100×100×100 mm. The temperature control of the concrete mixture was carried out using a system of automated temperature and strength monitoring of concrete. This system includes temperature sensors that are embedded in the void former, a recorder module, and a device for accessing the received information. During the experiment, it was found that to gain strength of the concrete mixture, additional heating of the duct former is required using heating wires with a winding pitch of 100 mm. In this case, even at an external air temperature of -15 °C, the temperature of the concrete mixture does not fall below zero, respectively, the concrete continues to gain strength.

FOR CITATION: Rumyantsev E.V., Shvetsova V.A. Development of a system for monitoring the hardening of prefabricated reinforced concrete joints at negative temperatures // Technique and technology of silicates. 2022.Vol. 29. No1. Pp 4 – 15.

KEY WORDS:

ultra-high performance concrete, fiber reinforced concrete, steel fiber, UHPC, UHPFRC, aggregate

ABSTRACT:

The article presents the experimental results of the study of the flexural and compressive strength of ultra-high performance concrete (UHPC), as well as the fracture toughness depending on the volumetric content of steel fiber and aggregate. Self-compacting fiber-reinforced concretes with compressive strength over 150 MPa were obtained. It was found that by increasing the aggregate content in concrete from 0.33 to 0.44 m³ the fiber content could be reduced from 3 to 1.5% while maintaining similar values of flexural strength and fracture toughness. It was established that fiber-reinforced concrete with volumetric aggregate content of 0.44    has higher strength characteristics after the formation of the main crack: at the fiber content of 1.5 % the value of bending stress increases from 24.5 to 27.6 MPa, reaching a maximum at a deflection value of 1.16 mm; at the fiber content of 3 % the value of bending stress increases from 30.7 to 35.5 MPa, reaching a maximum at a deflection value of 1.38 mm. A result of the studies is an establishment of the possibility of increasing the volume fraction of aggregate in fiber concrete from 0,33 to 0,44 m³, which allows reducing the content of the most expensive component - steel fibers from 3 to 1,5%, and thus providing equal strength in compression and bending, as well as increasing to 50% the fracture toughness.

FOR CITATION: Soloviev V., Matiushin E., EfishovL. Influence of steel fiber and aggregate volume content on the properties of ultra-high performance fiber reinforced concrete // Technique and technology of silicates. 2022. Vol. 29. No1. Pp 16 – 26.

KEY WORDS:
X-HVY concrete, shotcrete, segregation, python, AI, coarse aggregate

ABSTRACT:

This article evaluates the effect of stratification for particularly heavy concretes and provides theoretical calculations to determine the dependencies that affect the values of stratification, such as shear stress and density. An algorithm is presented and the program itself is laid out to determine the coarse aggregate content of a cross-sectional image of concrete. A comparative analysis of three methods: graphical, programmatic and coarse aggregate scattering is performed. The work of the program is based on the work of AI on the library OpenCV in Python, the error in calculating the area in comparison with the direct method is about 4-5%. All tested samples were kept in a chamber of normal hardening for 28 days, using coarse aggregate of barite and quartz iron with a density of 3.9 g/cm³.

FOR CITATION: Sizyakov I Segregation study based on the program to determine the coarse aggregate content in the sample section// Technique and technology of silicates. 2022. Vol. 29. No1. Pp 27 – 36.

KEY WORDS:

modified concrete, irrigation and drainage construction, polydisperse binder, superplasticizer, complex polymer additive, strength, water absorption, water resistance, frost resistance cement systems, nanomodification, nanosized additives, long-term hardening, long-term strength

ABSTRACT:

The main task of obtaining concrete, in particular for irrigation and drainage construction, with increased performance by modifying their structure and properties with complex additives is becoming more and more relevant every year. Within the framework of these studies, issues related to the modification of the composition of heavy concrete with the use of a complex chemical additive consisting of the superplasticizer Melflux 5581 F and the water-soluble polymer additive Polydon-A were considered. The aim of the study is to develop a scientifically based technological solution that provides the production of heavy concrete based on a polydisperse binder with a complex polymer modifier (Melflux + Polydon-A) for irrigation and drainage construction. The object of study is heavy concrete based on a polydisperse binder with a complex polymer modifier. The resulting modified concrete is characterized by an increase in compressive and tensile strength in bending, a conditional stress intensity factor, water absorption, water resistance and frost resistance, which makes it possible to recommend it for the production of building products and structures operating in harsh operating conditions, in particular, for trays irrigation systems.

FOR CITATION: Kaddo M.B., Filimonova YU.S. Study of modified heavy concrete based on polydisperse binder with complex polymer modifier// Technique and technology of silicates. 2022. Vol. 29. No1. Pp 37 – 44.

KEY WORDS:

reinforced concrete structure; concrete corrosion; Henry's law; mathematical modelling; concrete - soil – liquid

ABSTRACT:

The paper considers methods of physical and mathematical modeling that can be used to describe the processes of non-stationary mass transfer of free calcium hydroxide in buried concrete and reinforced concrete structures of coastal zones. The authors proposed a mathematical model of mass transfer in an unrestricted two-layer plate in the form of a system of parabolic partial differential equations with boundary conditions of the second kind at the "concrete-liquid" interface and of the fourth kind at the "concrete-soil" interface. In terms of the results of experimental studies of the mechanisms for reducing the quality of concrete due to exposure to sulfate and acidic environments, using the obtained solutions of the mathematical model, it becomes possible to select the optimal composition of concrete with high anticorrosion properties.

FOR CITATION: Fedosov S.V., Aleksandrovа O.V., Nguyen Duc Vinh Quang1, Fedoseev V.N., Loginova S.A. Physical-mechanical foundations of theoretical and engineering investigation on the development to corrosion-resistant materials in buried structures of coastal zones// Technique and technology of silicates. 2022. Vol. 29. No1. Pp 45 – 54.

KEY WORDS:

reinforced concrete structure, concrete corrosion, non-stationary mass transfer, Fourier numbers, free calcium hydroxide, mathematical model.

ABSTRACT:

This paper considers the basic methods of physical-mathematical modeling that are used to describe the processes of non-stationary mass transfer of "free calcium hydroxide" in concrete structures placed in a liquid environment with a defined flow rate. The boundary value problem of "free calcium hydroxide" mass conductivity in dimensionless variables is obtained. To demonstrate the possibilities of the obtained solution, we will carry out a numerical experiment: in which the fluctuation in the field of dimensionless concentrations by the different values of the Fourier number, in accordance with the theory of similarity, will be considered as an indicator of the process time. The study indicated the results of calculating the concentration distributions "free calcium hydroxide" over the dimensionless thickness of the concrete structure at Fourier numbers 0.01; 0.1; 0.2; 0.5 and 1. The study also provides an example of determining the time of reaching the coastal structure surface critical concentration "of free calcium hydroxide" leading to the beginning of high-basic cement concrete. Analysis of the solution also makes it possible to determine the duration of the service life of a reinforced concrete structure, which is determined by the processes occurring at the interface: in concrete - mass conductivity (k), and in the liquid phase - mass transfer (β).

FOR CITATION: Fedosov S.V., Bulgakov B.I., Krasilnikov I.V., Ngo Xuan Hung, Tang Van Lam Forecast of durability of shore structures made of reinforced concrete // Technique and technology of silicates. 2022. Vol. 29. No1. Pp 55 – 63.

KEY WORDS:

high-strength concrete, powder-activated concrete, multilevel dispersion-granulometric modification, structural level, Portland cement fractions, pozzolanic reaction

ABSTRACT:

The main disadvantages of high-strength concretes currently used are the high absolute and relative consumption of the binder per unit strength. The solution of the marked problem seems to be possible by using dispersed highly effective mineral and chemical modifiers that provide a multilevel modification of the particle size distribution with a high level of solid phase concentration per unit volume and a uniform pozzolanic reaction at all structural levels. When used as components stimulating the occurrence of a pozzolanic reaction between particles of all structural levels, two fractions of clinker cement provide an increase in strength by almost 2 times in comparison with the initial composition. Multilevel modification of the particle size distribution in combination with the use of two fractions of Portland clinker cement contributes to the formation of a dense structure of high-strength powder-activated concrete with a high concentration of the solid phase per unit volume and crystallinity, as well as high physical and mechanical properties.

FOR CITATION: Samchenko S.V. Kaprielov S.S., Дыкин И.В. Optimization of the structure and properties of powder-activated concrete by using Portland cements of various dispersions // Technique and technology of silicates. 2022. Vol. 29. No1. Pp 64 – 74.

KEY WORDS:

concrete, graphic concrete, retarders, retarding admixtures, landscape design

ABSTRACT:

Concrete can justly be classified as one of the most multifunctional construction materials due to the unique combination of its characteristics, such as strength, durability, water resistance, fire resistance. However, nowadays, concrete has been actively used not only in the field of construction industry when designing load-bearing structures made of reinforced concrete. Landscape designers create truly unique art objects of aesthetic and functional purposes in a park and urban environment. The manufacturing process of graphic concrete includes several main stages, the most important one is the application of a concrete retarder to a special membrane. Currently, a large number of retarders which differ from each other in mechanism of action and price are known. These admixtures are usually applied in different quantities, they can slow down the setting time of cement dough at different depths, which ultimately affects the visual and decorative effect of the surface in various ways. The objective of the study is to study various types of retarders suitable for such an innovative technology as graphic concrete, where there is not much theoretical and experimental knowledge has been accumulated so far. The methodological basis is the analysis of literature data on application of retarding admixtures for concrete surface treatment. The result of the study is a list of retarding additives for concrete mixture that can be successfully used in graphic concrete technology.

FOR CITATION: Zemskova O.V., Dudareva M.O. Modern technologies of concrete decoration in the urban landscape // Technique and technology of silicates. 2022. Vol. 29. No1. Pp 75 – 81.

KEY WORDS:

lightweight concrete, slag-alkali binders, cellular structure, porous wood concrete, stabilizer additives, hydration kinetics

ABSTRACT:

Obtaining a strong and uniform cellular structure, which is able to provide the required characteristics of the composite at constant density values, is an urgent issue for the production of porous wood concrete. Positive results in the formation of the structure of porous wood concrete can be achieved by improving the properties of technical foam through the use of stabilizer additives. The article considers the formation of the porous structure of slag-silicate porous arbolite. To improve the quality of technical foam, various stabilizer additives: bentonite clay, liquid glass and sodium humate were used. It has been established that the addition of bentonite clay affects the properties of the resulting foam to a greater extent. When clay is added in an amount equal to 4% by weight of the foaming agent solution, water separation is reduced to 28.2% without changing the multiplicity relative to the control sample. Also, studies of the hydration kinetics of the slag-silicate binder were carried out using the method of isothermal calorimetry. A slight slowdown in the processes of hydration and a decrease in heat release for a sample with a surfactant was shown, which is due to the high adsorption capacity of surfactant molecules, which slow down the processes of structure formation, and can also affect the morphology of the neoplasms of the composite.

FOR CITATION: Dvornikov R.M., Samchenko S.V. Formation of the cellular structure of porous wood concrete // Technique and technology of silicates. 2022. Vol. 29. No1. Pp 82 – 91.