2021

Archives Journal Construction Materials and Products Vol. 4

ANALYSIS OF THE EFFECT OF METHODS OF INTRODUCTION OF ORGANOMINERAL ADDITIVES INTO MORTARS ON FINE SANDS

https://doi.org/10.34031/2618-7183-2021-4-4-32-40
Abstract
The use of technogenic raw materials in the production of building composites is an urgent direction in the technology of production of building materials in view of its economic efficiency, environmental effect and wide possibilities of their application. Recently, the issues of environmental safety in the production of building materials, the possibility of their processing and disposal have come to the fore. All this is dictated by the need for energy and resource conservation, the massive depletion of natural reserves and the progressive pollution of the environment due to anthropogenic activities. Construction composites provide ample opportunities for recycling of secondary raw materials, as their structure allows them to be used not only as a filler, but also in some cases as additives for regulating certain properties. More studied and widely used are ash and slag mixtures on the basis of which various organomineral additives are developed. So, on the territory of the Chechen Republic there are dumps of ash and slag mixtures, which, according to their chemical and mineralogical composition, are suitable for the design of organomineral additives and fillers in construction concretes and solutions. Building solutions are widely used for interior and exterior finishing works during the construction of construction projects in the Chechen Republic, which is characterized by high humidity in the winter, which provokes deformations of the plaster layer on facades. In this article, the development of an organomineral additive based on an ash-slag mixture is considered to improve the quality of mortar mixtures resistant to such conditions.
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EXPERIMENTAL STUDY OF PLATES FOR PUNCHING UNDER DYNAMIC LOADING

https://doi.org/10.34031/2618-7183-2021-4-4-41-48
Abstract
The issues of strength and deformability of reinforced concrete floors during punching remain insufficiently studied at present, despite the available publications in the technical literature. This article presents the results of experimental studies on punching of fragments of conjugation of flat reinforced concrete monolithic slabs with a column under dynamic loading. The purpose of these studies was to obtain experimental data on the stress-strain state of a fragment of a monolithic floor during dynamic punching with varying thickness and class of concrete, to reveal the failure patterns of experimental samples, and to obtain new experimental data. A setup for dynamic testing is described. Comparison of breaking load for specimens tested under dynamic loading with breaking load for specimens tested for static load is presented. The angles of inclination of the punching shear pyramid under static and dynamic loading are indicated.
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OBTAINING A THERMAL INSULATION LAYER FROM MONOLITHIC NON-AUTOCLAVED STRUCTURAL AND THERMAL INSULATION FIBRE FOAM CONCRETE

https://doi.org/10.34031/2618-7183-2021-4-3-5-22
Abstract
The possibility of obtaining structural and thermal insulation foam concrete of non-autoclave hardening with improved construction and technical characteristics for the device of a thermal insulation layer in the con-struction of road pavement due to three-dimensional dispersed reinforcement with polypropylene fiber is theoretically justified and experimentally confirmed. Based on the results of studies of the influence of technological factors on the properties of foam concrete, the optimal content (up to 0.25% of the cement mass) and the length (12 mm) of reinforcing polypropylene fibers have been established, which allows obtaining high strength indicators of dispersed-reinforced cement stone for bending (an increase of 12-20%) and compression (an increase of 6-12%) compared with non-reinforced cement stone of non-autoclaved foam concrete. The analysis of the process of structure formation of dispersed reinforced foam concrete from the standpoint of a systematic approach based on multifactorial polynomial models of the influence of the ratio of filler and binder, as well as the number of dispersed reinforcing fibers, which is determined by the optimal conditions for the distribution of solid and gas phases, as well as the reinforcement of adjacent interstitial partitions of foam concrete, linking them into one asociate, which ensures the joint work of the material under various external influences. A method was developed to increase the durability of the road surface and eliminate the influence of the frost heaving effect on the quality of the road surface by introducing the necessary amount of effective thermal insulation layer into the road surface design. The analysis of the regularity of the heat transfer process in the soil mass of the roadbed and multilayer road pavement is carried out. Based on the analysis, the values of the necessary resistance to heat transfer of road pavement for the natural and climatic regions of the country are determined and a method for calculating the value of the thermal insulation (frost-proof) layer of road pavement is proposed. A method was developed for calculating the value of the thermal insulation layer using monolithic fibre foam concrete and a nomogram to determine the required value of the thermal insulation layer made of monolithic non-autoclaved structural and thermal insulation fibre foam concrete of classes D600-D1000.
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EXERGETIC ANALYSIS OF A BUILDING AS A KEY ELEMENT OF A HEAT SUPPLY SYSTEM

https://doi.org/10.34031/2618-7183-2021-4-3-23-40
Abstract
The study of the complex influence of weather and climatic factors and their variability on the needs of energy and exergy when creating thermal comfort in a house with various engineering and architectural characteristics is carried out. It is confirmed that even for houses with relatively low thermal characteristics built in accordance with regulatory documents, the role of solar radiation in the formation of the heat balance, especially at the beginning and end of the heating season, is important. Studies showed that due to the combined influence of external meteorological factors, with the improvement of the thermal characteristics of houses, the correlation between the energy demand for creating a favorable microclimate and the outdoor air temperature significantly worsens. It is determined that in this case, the value of the approximation reliability decreases from 1 (with a linear dependence) to 0.55 and lower (with the maximum possible improved thermal characteristics of the house today). This position significantly corrects the operating modes and characteristics of the ST. In particular, this makes it necessary to improve the automatic control system of ST. And this, in turn, increases the investment component of the system. A method was developed for calculating exergy needs to create thermal comfort inside the house by taking into account, using the probability theory, the influence of the random nature of meteorological factors within the heating period, on the basis of which, in the conditions of the region, it is shown and calculated that when de-termining the seasonal exergy needs for the heat supply of the house, the use of a stationary approach leads to an underestimation of the results by 12...28% compared to the dynamic approach.
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IMPROVING THE CALCULATION OF FLEXIBLE CFST-COLUMNS, TAKING INTO ACCOUNT STRESSES IN THE SECTION PLANES

https://doi.org/10.34031/2618-7183-2021-4-3-41-53
Abstract
The article is devoted to a newly developed complex finite element that allows modeling concrete-filled steel tubular columns taking into account the compression of the concrete core from the steel tube, as well as geometric nonlinearity. The derivation of the resolving equations, as well as expressions for the elements of the stiffness matrix, is based on the hypothesis of plane sections. The complex testing of the finite element was performed using the program code written by the authors in the MATLAB language and the ANSYS software, as well as the analysis of the effectiveness of the new FE in comparison with the classical methods of modeling CFST-columns in modern software systems. A significant decrease in the order of the system of FEM equations is demonstrated in comparison with the modeling of CFST-structures in a volumetric formulation in existing design complexes using SOLID elements for a concrete core with 3 degrees of freedom in each of the nodes, and SHELL elements for a steel tube with 6 degrees of freedom in each of the nodes, with a comparable accuracy in determining the stress-strain state. The behavior of steel and concrete in the presented work is assumed to be linearly elastic, however, the described calculation method can be generalized to the case of using nonlinear deformation models of materials.
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MODIFIED CAM-CLAY MODELS FOR DYNAMIC ANALYSIS OF GRANULAR METAMATERIALS IN EARTHQUAKE ENGINEERING

https://doi.org/10.34031/2618-7183-2021-4-3-54-60
Abstract
the problem of protecting buildings and structures from vibrations of natural and artificial nature is important for modern construction. One of such modern methods of protection is seismic pads. The purpose of this work was to study the effect of adding a layer of granular metamaterial under a slab foundation on the vibration of a building under the influence of seismic shear waves (S-waves). To achieve this objective, the finite element method (FEM) was used in combination with Cam-Clay models. The FE model consists of a ten-story superstructure rested on the slab foundation, under which there is a layer of granular metamaterials. 16 models were created taking into account changes in the values of these parameters (pad thickness; density; cohesion; critical state strength parameter (M); Young's modulus-Poisson's ratio). The dynamic analysis performed using the software package Abaqus/CAE showed the effectiveness of granular metamaterials in their ability to dissipate seismic energy and significantly reduce vibration transmitted from the ground to the building.
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DRUCKER-PRAGER MODELS FOR DYNAMIC ANALYSIS OF GRANULAR METAMATERIALS IN EARTHQUAKE ENGINEERING

https://doi.org/10.34031/2618-7183-2021-4-2-5-11
Abstract
Problem of developing methods for protecting buildings and structures from the vibrations transmitted to them from the soil under the action of seismic effects is extremely important to date. One of these modern methods is seismic pads. The purpose of this work was to study the effectiveness of adding a pad of granular metamaterials under the foundation of the building to decrease influence of seismic shear waves. The Finite Element Analysis of Mohr-Coulomb models was used to achieve this goal. The FE model consists of a ten-story superstructure rested on the slab foundation, under which there is a layer of granular metamaterials. The values of five variables that affect the mechanical properties of these metamaterials were analyzed (density – cohesion – internal friction angle – Young's modulus – Poisson's ratio) for two different pad thicknesses. The dynamic analysis performed using the software package Abaqus/CAE showed the effectiveness of the granular metamaterials in their ability to significantly reduce magnitudes of displacements, velocities and accelerations in the building compared to the same values in the absence of these metamaterials. The analysis also revealed that among the studied variables, the cohesion is the parameter most influencing the effectiveness of metamaterials in their ability to dissipate seismic waves, while no significant effect was observed for the other parameters.
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AN EFFECTIVE WAY TO RECYCLE 3D PRINTING CONCRETE SCRAP

https://doi.org/10.34031/2618-7183-2021-4-2-12-18
Abstract
The article proposes a rational method for processing 3D printing concrete scrap using vibration equipment, which allows obtaining a multicomponent building material with minimal electricity consumption. As a criterion for the degree of grinding of concrete scrap, it is proposed to use the specific surface area of the finely dispersed part of concrete scrap, which should correspond to 400-500 m2/kg. The possibility of reusing the resulting product instead of the traditional fine aggregate of quartz sand is shown. It was found that the concrete scrap without the addition of Portland cement hardens, reaching up to 48% of the compressive strength of the control samples by 28 days. When 10% of the binder CEM I 42.5 N was added to the concrete scrap processing product, the compressive strength of fine-grained concrete increased by 106.6%, and 20% of Portland cement - by 112.2 %, compared to the strength of control samples of a similar composition on traditional quartz sand after 28 days of hardening. It is noted that this is primarily due to the weak contact zone of quartz sand and the cement matrix of concrete. The use of the product of processing concrete scrap allows obtaining building composites based on it with the complete exclusion of natural raw materials.
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WORLD EXPERIENCE IN THE CONSTRUCTION OF GRAVITY DAMS FROM A PARTICULARLY LEAN CONCRETE MIX

https://doi.org/10.34031/2618-7183-2021-4-2-19-28
Abstract
The article discusses the main aspects of the construction of dams with a symmetrical profile from the material "solid embankment" or other names ("lean" concrete, cemented "sand and gravel mixture" CSG). The design of typical profiles of dams of implemented projects is considered, and information regarding the characteristics and methods of production of this material is provided. The main properties of this material and the principle of its preparation are considered. The work in this area of engineers from Russia, Japan, Iran, Korea, China, and Turkey is analyzed. These dam structures are characterized by high reliability and efficiency, but also, most importantly, by a much higher adaptability or high speed of construction, which is little dependent on local natural factors than traditional rolled concrete dams.
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NONLINEAR TRANSVERSE VIBRATIONS OF COMPOSITE RODS UNDER THE ACTION OF A STATICALLY APPLIED TRANSVERSE LOAD

https://doi.org/10.34031/2618-7183-2021-4-2-29-37
Abstract
Nonlinear transverse vibrations of composite rods pre-loaded with lagging arranged symmetrically on both sides of the axis of the composite rod under the action of a statically applied transverse load are investigated. The cases of attaching the lagging only to the ends of the composite rod, as well as when the laggings are continuously attached to the composite rod along its entire length, are considered. The results of the study of nonlinear transverse vibrations of composite rods under the action of a statically applied transverse load are presented. When conducting studies of transverse vibrations of composite rods, solutions of differential equations of vibration of prestressed through beams and stiffening cores of high-rise buildings are obtained. The obtained differential equations of vibration of composite rods allow us to determine the dynamic characteristics of prestressed through beams under various linear and boundary conditions. A method for composing differential equations of free and forced oscillations of prestressed through beams and stiffening cores of high-rise buildings and solving differential equations under various linear and nonlinear boundary conditions is developed.
Expressions are given for determining the longitudinal forces and torques at the ends of the rod at any location of the lagging from the axis and at any different stiffness of the lagging.
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