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Vol. 2 Issue 3

Archives Journal Construction Materials and Products Vol. 2 Issue 3

CHEMICAL REACTIVITY ASSESSMENT METHOD OF NANOSTRUCTURED LOW CALCIUM ALUMINOSILICATES

https://doi.org/10.34031/2618-7183-2019-2-3-5-11
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 5-11 p.
Abstract
Nowadays, the production of high-performance composites is a relevant objective in construction industry. Normally, geological and/or technological conditions of phase formation are responsible for chemical and structural characteristics of raw materials. In this regard, the use of a certain material dictates terms to opti-mizing production process, efficient use and, therefore, requires to develop a method for quality evaluation of raw materials. This approach allows a considerable time saving and raw materials sources, while the evaluation of final performance characteristics of designed materials is being done. The biggest interest in this area is focused on new types of developed and poorly-studied composite systems which results in a lack of capacity to design materials with known performance and, therefore, constrains the areas of application of construction composites
Among such composite systems there are zero cement alkali-aluminosilicate systems or geopolymers. For geopolymers production a wide range of different aluminosilicates with varied characteristics potentially can be used. And also, in each certain case, the quality evaluation methods for aluminosilicates should be different.
This study is focused on chemical reactivity assessment method of crystalline (mainly, nanocrystalline) low calcium aluminosilicates exposed to high-alkali media. The solubility degree in high-alkali media and compressive strength performance were evaluated in this study in order to define chemical reactivity of low calcium aluminosilicates. The compressive strength data demonstrated a positive correlation with the crystallinity degree of aluminosilicates.
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APPLICATION OF STEPWISE AND ITERATIVE METHOD IN THE CALCULATION OF BENDING PRESTRESSED PRECAST AND MONOLITHIC ELEMENTS TAKING INTO ACCOUNT PHYSICAL NONLINEARITY

https://doi.org/10.34031/2618-7183-2019-2-3-12-27
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 12-27 p.
Abstract
Precast and monolithic reinforced concrete structures with and without prestressing armature voltages are used as newly designed independent ones, and are the result of work to strengthen existing structures by in-creasing the cross section. In both cases, the cross-section of such elements is considered as a two-layer, and the resulting composite element operates under load in conditions distributed between the layers of internal forces, the mechanism and the actual value of the distribution of which depends on the physical and mechanical characteristics, the design scheme and the parameters of the contact interaction of the layers. When calculating and designing prestressed reinforced concrete precast and monolithic elements, the shear seam compliance is usually not taken into account, which complicates the analysis of the actual stress-strain state of the structure and contains a certain undisclosed potential for its rational design. One of the possible directions in solving the problem, taking into account the shift of the contact seam, is the use of variational principles of structural mechanics in the calculation of structures such as composite cross-section rods. In the framework of this work, the questions of practical applicability in the structural analysis of composite reinforced concrete precast-monolithic rod of variation principles of structural mechanics based on the method of V.Z. Vlasov – I.E. Mileykovsky in the form of displacements in combination with the stepwise-iterative method of calculation are considered. The results of numerical calculations by the proposed method are presented, which allows to take into account the specifics of the shear bonds of the precast and mono-lithic layer, to carry out practical accounting of the seam compliance, as well as to take into account the physical nonlinearity of the characteristics of materials, which allows the rational design of precast monolithic structures.
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EVALUATION OF THE SEISMIC INERTIA FORCES ON THE ACTUAL DAMAGE OF BRIDGES

https://doi.org/10.34031/2618-7183-2019-2-3-28-33
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 28-33 p.
Abstract
Because of the constant threat of earthquakes in seismic hazardous areas, it is necessary to study the issues of seismic resistance of structures and development of methods of their design, taking into account the seismic factor. A significant share in the total volume of engineering structures permanent and built on canals and roads is occupied by artificial structures, such as aqueducts, small and medium bridges (overpasses). In this regard, the provision of seismic resistance of these structures is of practical interest. Buildings and structures located in seismic areas are affected by factors that cause the occurrence of seismic forces and changes in the working conditions of structures during earthquakes The article presents the results of comparison of calculations in the dynamic theory (by the method of spectral curves) and static seismic coefficient determination with the actual data on damage to structures in strong earthquakes. A formula for calculating the coefficient of seismicity is proposed.
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RELEVANCE OF THE CREATION OF ARTIFICIAL BREATHING ATMOSPHERES IN TERMS OF AIR POLLUTION

https://doi.org/10.34031/2618-7183-2019-2-3-34-40
 34-40 p.
Abstract
At present, the problem of air quality in large cities with a large number of cars and industrial enterprises is acute. Normative documents on the basis of which the ventilation system is designed regulate the cleaning of the outside air from dust. Purification from gaseous contaminants as well as suspended aerosols such doc-uments do not regulate. According to the results of the study of air quality in Moscow over the past few years, an increased content of pollutants such as NO, CO, CO2, SO2 has been registered. Near busy highways during “rush hours” the vehicles locally “burn” oxygen in the air and emitted products of combustion even more reduce the relative concentration of oxygen in the air. Also, a large number of pollutants come from industrial and agricultural enterprises. The use of additional purification filters in ventilation systems, such as photocatalytic filter, adsorption filter can reduce the concentration of gaseous pollutants to an acceptable minimum, but they will not solve the problem of low oxygen content. Inhalation of air in excess of MPC for a long time may cause irreversible health effects. In this regard, the task of creating artificial respiratory atmospheres becomes relevant. The greatest relevance of air quality and sufficient oxygen content is for children's institutions, as well as special services, the work of which is associated with an increased concentration of attention. The problem of air pollution with aerosols and fine dust has become particularly relevant due to the significant increase in respiratory tract diseases and various allergies.
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FOR THE STUDY OF PECULIARITIES OF STRUCTURE FORMATION OF COMPOSITE BINDERS FOR NON-AUTOCLAVED AERATED CONCRETE

https://doi.org/10.34031/2618-7183-2019-2-3-41-47
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 41-47 p.
Abstract
The basis of the modern market of cellular concrete is autoclaved gas silicate. At the same time, non-autoclaved aerated concrete is largely a more technological material, allowing the variation of its properties within a wide range, having a potentially wider field of application, less costly in the organization of production, which is of great importance for small and medium-sized businesses. The main problem of non-autoclaved aerated concrete is a higher cost of raw materials compared to silicate, and 20...30% lower strength performance. The proposed solution to this problem is the development of special composite binders with a limited content of clinker and mineral additives of various genetic types, taking into account the peculiarities of the two-stage structure formation of the material – gas porization and the formation of the microstructure of the stone. The article deals with some aspects of the interaction in the system “mineral additive – gypsum – by-products of the gas release reaction” in terms of the effect on the viscosity of the swelling mass and the strength of the stone at different times of hardening. Recommendations are given on the preferred compositions of composite binders and dosages of gypsum in the molding mixture when producing a material with an average density in the range of 500...700 kg/m3.
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NUMERICAL CALCULATION OF STRESS-STRAIN STATE OF EARTH DAM UNDER BASIC LOADS WITH ACCOUNT OF INHOMOGENEOUS FOUNDATION

https://doi.org/10.34031/2618-7183-2019-2-3-48-57
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 48-57 p.
Abstract
Design, construction and operation of earth hydrotechnical structures located in seismic regions require a continuous improvement of computational methods for calculating various loads (static and dynamic ones). On the basis of the developed methodology and the complex of applied programs, an earth dam (Tupolang HPP) is calculated for the basic loads (gravity forces, hydrostatics) taking into account the design features and the actual physical and mechanical characteristics of soil both at the structure and at its earth foundation ( the height of the structure is 165m).The problem is solved in a plane elastic statement by the numerical finite element method. As the result of the calculation the isolines were obtained of equal displacements (horizontal and vertical), stresses (normal, tangential, principal) over the area occupied by the structure and its inhomogeneous foundation. A number of physical conclusions were made regarding the construction of important structures on an inhomogeneous earth foundation.
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THE USE OF COMPOSITE MATERIALS IN RECONSTRUCTION OF FLOORS OF INDUSTRIAL BUILDINGS

https://doi.org/10.34031/2618-7183-2019-2-3-58-64
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 58-64 p.
Abstract
The article discusses the relevance of the use of composite materials in the reconstruction of exposed to heavy loads of concrete and reinforced concrete floors of industrial buildings. It is noted that at the present stage of development of the construction industry special attention is paid to the use of steel fibreconcrete, as this material allows with minimal material and labor costs to carry out work on the reconstruction of industrial floors. The novelty of this study is the use as an adhesive between the existing floor, which is to be restored and strengthened, and the newly laid steel-fiber concrete layer of polymer-bitumen composite material with the addition of cement and graphite powder, previously obtained by the authors experimentally. This material with the required thickness is also a structural layer for leveling the surface of the lower layer, reducing friction under the sole of the upper steel-fiber concrete layer and the existing floor. The paper presents the technology of work in the reconstruction. The composition of the steel-fiber concrete layer is adopted on the basis of studies by other authors. Despite the fact that the experiments proved the solidity and strength of the reconstruction of the floor by the developed technology, the article notes that the final characteristics of the proposed floor design and technology can be identified only during operation, which can be the basis for further research on optimizing the thickness of the layers proposed for use of composite materials. For the evaluation of economic efficiency of application of these composite materials in the reconstruction of the concrete floors in the course of the experiment, there are revealed some figures for labor and material costs.
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DIRECTED REGULATION OF PROPERTIES OF ASPHALT CONCRETE BY NANOCARBON OBJECTS

https://doi.org/10.34031/2618-7183-2019-2-3-65-71
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 65-71 p.
Abstract
Directed regulation of asphalt concrete properties is an important condition for obtaining a durable material that minimizes operating costs. One of such perspective directions is modification of building compositions by nanoscale objects. The method of modification of mineral powder from dolomite by carbon nanotubes is considered in the work, and results of tests of asphalt concrete on its basis are given. It is shown that the use of nanomodified dispersed dolomite in the technology of preparation of asphalt concrete mixture on the surface of the grains of mineral material forms a strong, high-temperature resistant layer of structured bitumen. The increase in the dynamic viscosity of bitumen and the complex shear modulus under the influence of CNT contributes to the change in the yield strength of asphalt concrete above the maximum shear stresses, which leads to a slight accumulation of residual plastic deformations in the plate in the study of the resistance to ruts. Thus, modification of bitumen and asphalt concrete with nanoscale additives can be an effective tool in the fight against plastic deformations such as shifts, surges and rutting in hot climates, for example, in Jordan.
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THE CONCENTRATION OF THERMAL STRESSES IN METAL MATERIALS AND CONSTRUCTION UNDER LOCAL HEATING

https://doi.org/10.34031/2618-7183-2019-2-3-72-77
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 72-77 p.
Abstract
Significant thermal stresses arising in thin-walled metal materials and structures loaded with tensile stresses can lead either to their complete destruction or to the appearance of discontinuity zones in them. The equa-tions for calculation of temperature stresses in flat thin-walled structures at their localized thermal heating caused by the action of concentrated energy flows are analyzed. As an example, a thin-walled stretched plate subjected to strong local heating in a circular spot is considered. The developed model takes into account the change of elastic characteristics under strong local heating and the change in the thickness of the material in the heating spot. As an example, the diagram of the distribution of tangential stresses for a stretched plate in the area of a circular heating spot is given. Thus, the results of the study show that there is a rupture and concentration of stresses along the contour of the heating spot from the cold zone.
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ENVIRONMENTAL MONITORING OF ECOLOGICAL SAFETY IN AREAS OF CONSTRUCTION, RECONSTRUCTION AND OPERATION OF OBJECTS

https://doi.org/10.34031/2618-7183-2019-2-3-78-84
 78-84 p.
Abstract
Environmental monitoring of construction production should use modern scientific and technical method of physical, chemical and biological control for periodic or continuous monitoring and measurement of factors associated with chemical pollutants and physical and biological pollution on the spot, and for the correct assessment of environmental quality.
For a construction project, all stages of construction production need environmental monitoring due to different monitoring purposes.
During the entire construction period, environmental monitoring can accurately, timely, comprehensively reflect the impact of construction work on the site and the environment and provide a scientific basis for environmental management. Continuous monitoring provides real-time, up-to-date results to help environmental management professionals understand environmental quality in a site and be able to respond in a timely manner.
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