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Keywords: strength

AN EFFECTIVE WAY TO RECYCLE 3D PRINTING CONCRETE SCRAP

https://doi.org/10.34031/2618-7183-2021-4-2-12-18
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 12-18 p.
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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EFFECT OF WOLLASTONITE ON THE MECHANICAL CHARACTERISTICS OF CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-5-34-42
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 34-42 p.
Abstract
Improvement of the physical and mechanical properties of cement composites should be accompanied by the disposal of industrial waste of various generation. Therefore, the paper proposes the principles of con-trolling the strength properties of concrete, which consist in the complex effect of wollastonite obtained from boron production waste on the processes of structure formation of the cement matrix. When this introduced in an amount of 2-8 wt. % wollastonite has a dual function as a mineral filler and a reinforcing fiber. It has been proven that in the presence of wollastonite, the concrete mix becomes lighter without reducing its physical and mechanical properties. It was revealed that the early strength for all the developed compositions with the addition of wollastonite increases due to the acceleration of hydration processes. Calcium silicate, which is wollastonite CaSiO3, has a close chemical composition with cement clinker, especially with Ca2SiO4 belite and Ca3SiO5 alite. This leads to the formation of a chemically homogeneous and, as a result, hardened microstructure. Elongated wollastonite fibers with good adhesion to the cement stone provide effective micro-reinforcement of the concrete composite. Using the results will lead to the possibility of designing high-strength concretes, including for special structures.
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EFFECT OF POROUS STRUCTURE ON SOUND ABSORPTION OF CELLULAR CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-2-5-18
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 5-18 p.
Abstract
The compositions of gas and foam concrete with improved acoustic characteristics were developed. The optimal form of porosity, which contributes to the absorption of sound waves, both in the range of audible frequencies and at infrasonic and ultrasonic frequencies, is revealed. The mathematical model for designing sound-absorbing concrete was improved, taking into account both the porosity of the composite and the influence of the porous aggregate. The laws of synthesis of aerated concrete and foam concrete are established, which consist in optimizing the processes of structure formation due to the use of a polymineral cement-ash binder and blowing agent. The composition of the composite intensifies the process of hydration of the system, which leads to the synthesis of a polymineral heterodisperse matrix with an open porosity of more than 60%. Peculiarities of the influence of the “Portland cement – aluminosilicate – complex of modifiers” system on the rheology of the concrete mixture was identified, which can significantly reduce shear stress and create easily formed cellular concrete mixtures. The increased activity and granulometry of aluminosilicates predetermine an increase in the number of contacts and mechanical adhesion between particles during compaction, strengthening the frame of inter-pore septa. The mechanism of the influence of the composition of the concrete mixture on the microstructure of the composite is estab-lished. The presence of refined aluminosilicates and a complex of additives in the system along with cement contribute to the synthesis of the matrix with open porosity, thereby increasing the sound absorption coefficient.
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USE OF IRAQ CONCRETE SCRAP AS FILLER AND AGGREGATE OF HEAVYWEIGHT AND LIGHTWEIGHT CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-3-28-39
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 28-39 p.
Abstract
The relevance of the paper is due to the search for alternative sources of raw materials for the construction industry, associated with the disposal of man-made waste. The novelty of the article is to identify the sci-entific laws of the influence of demolition waste on buildings and structures on the formation of the microstructure of lightweight and heavyweight concrete. Concrete waste was prepared as both fillers of cement materials and fine aggregates, based on which concrete with high mechanical properties was created. The mix design was carried out from the point of view of geomimetics, in particular, taking into account the law of affinity of structures. The strength characteristics of concrete mixtures were investigated in accordance with EN 12390-3. In addition, the microstructural, morphological and thermal properties of the raw materials and concrete were determined during 28-day curing. For the first time, the dense microstructure of the composite was ensured, both with Portland cement products and with hydration, and, in part, with hydration products of previously unreacted clinker, whose minerals are present in concrete waste and are activated when they are crushed. The use of demolition waste of buildings and structures as a filler of cementing material when replacing Portland cement up to 20% allows to obtain better compressive strength of both heavyweight and lightweight concrete.
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EFFICIENCY OF STABILIZERS OF VARIOUS COMPOSITION FOR STRENGTHENING THE SOIL WITH A MINERAL BINDER

https://doi.org/10.34031/2618-7183-2020-3-1-30-38
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 30-38 p.
Abstract
The depletion of natural deposits of traditional inert mineral raw materials (sand, gravel) used to create effective layers of the foundations of roads leads to the development and application of new technologies and alternative materials. One way to solve this problem is to use local raw materials. For the construction of the lower layer of the road basement local soils are often used. However, their use is associated with the development of a set of measures to increase their efficiency, such as stabilization (by the use of chemical additives) and/or strengthening (by the introduction of various types of binders). In this regard, the paper analyzes the physicomechanical characteristics of reinforced clay soils obtained by introduction of various types of stabilizing additives in the presence of an inorganic mineral binder of hydration hardening type - cement - taking into account the recommendations for the used additives. The object of research was the most common representative of clay soils of the Belgorod region – heavy dusty clay loam. As a result of the studies, the authors established the reasonability of the use of the additives in the presence of cement, the most effective compositions of the reinforced soil were identified, contributing to the improvement of its controlled physical and mechanical characteristics. In addition, the need for additional studies to adjust the recommended composition of reinforced soil was established.
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EFFECT OF MICROFILLERS BASED ON NATURAL WOLLASTONITE ON PROPERTIES OF FINE-GRAINED CONCRETE

https://doi.org/10.34031/2618-7183-2019-2-6-20-28
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 20-28 p.
Abstract
The possibility of obtaining effective highly dispersed additives from natural wollastonite is substantiated and their influence on the properties of fine-grained concrete is investigated. On the basis of wollastonite, a complex micro-filler with particle sizes up to 100 microns was developed, obtained by joint grinding with quartz sand in a 3:1 ratio in a ball mill in the presence of an anionic surfactant naphthalene-formaldehyde type C-3 and a calcium stearate hydrophobizer technical C-17. A suspension of wollastonite with a modal particle diameter of 405 nm was obtained by pre-grinding wollastonite and anionic surfactant in a ball mill, with their further ultrasonic treatment in a bath-type activator. Mathematical models of the dependence of compression and bending strength on the content of the initial components are developed. It is established that the complex microfill leads to an increase in the strength of fine-grained concrete in bending by 2 times, in compression by 1.7 times with its content in the composition of fine-grained concrete in the amount of 10% by weight of cement. Wollastonite suspension increases the bending strength of fine-grained concrete to 3.1 MPa, compression to 57.8 MPa. The results of qualitative x-ray phase analysis showed that the total intensity of diffraction maxima of not fully hydrated alite C3S, belite C2S grains and their aggregates in cement stone with wollastonite decreases by 1.5-2 times compared to the control composition. This is most likely due to the amorphous nature of the wollastonite surface after grinding in a ball mill and ultrasonic dispersion in a bath-type activator. In addition, such particles are the centers of crystallization. Their needle-like shape contributes to the reinforcement of the structure by crystallizing new formations of cement stone.
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VITREOUS PROTECTIVE AND DECORATIVE COVERINGS ON WOOD PARTICLE BOARD

https://doi.org/10.34031/2618-7183-2018-1-4-4-12
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 4-12 p.
Abstract
Scientific and technological bases of receiving vitreous coverings on wood with use of a torch of low-temperature plasma are developed. Before plasma dusting of glass powders by grain structure 60-120mkm, the special protective coating protecting chipboard from destruction at high-temperature influence of a plasma stream on a front surface of the wood particle board (WPB) was applied. The structure of an intermediate protective coating including mix of a fine-grained glass powder and liquid glass is developed. Preliminary drawing an intermediate protective layer provides several consecutive technological operations.
For receiving vitreous coverings fight of colored and colourless glass are used which was previously ground in spherical porcelain mills. Optimum process parameters of plasma dusting of glass powder on the front surface of chipboard are developed. Optimum parameters of plasma melting is: current - 800A; operating voltage – 30B, a consumption of plasma-forming gas of argon 2m3/h.
Operational and aesthetic-consumer properties of vitreous protective and decorative coverings are investigated. It is established that vitreous protective and decorative coverings have the high durability of coupling with an intermediate protective layer. The received vitreous protective and decorative coverings on the basis of colored and colourless glass have the high water resistance, acid resistance, alkali resistance, as well as microhardness and high aesthetic performance.
The technology is recommended for widespread industrial introduction.
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ADDITIVE TECHNOLOGY IN CONSTRUCTION

https://doi.org/10.34031/2618-7183-2018-1-3-33-42
 33-42 p.
Abstract
The main innovative technologies of construction 3-D printing in modern construction are considered. This direction of research confirms the relevance of the selected issue. Development of compositions for building 3D printing allows for construction of not only individual constructions, but also buildings and constructions in general. Experimental compositions with effective for building print supplements will receive enough dense structure of concrete are developed. To assess the use of quartz sand for use in 3-d printers studies were conducted of their basic properties. The role of additive technologies in modern construction in the construction of buildings and structures that will lead to future changes in the construction market.
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INCREASING THE STRENGTH AND FROST RESISTANCE OF CERAMIC PRODUCTS AT USING MELASSES BARDS AS PLASTICIZER

https://doi.org/10.34031/2618-7183-2018-1-2-19-29
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 19-29 p.
Abstract
Ways of production of ceramic materials with use as the plasticizing additive of the sulphitic and alcohol bards (SAB), the calcium citrate filtrate (CCF) which is liquid withdrawal of production of citric acid in the microbiological way are known. However introduction to raw mix of CoB reduces forming humidity and fall of the formed products insufficiently, and an essential lack of FTsK is the low durability of products on compression with a big volume mass of samples.
In work the possibility of use as the plasticizing additive to a clay lot of withdrawal of the spirit industry – melasses bards is investigated. As a part of molasses the remains of amino acids and other organic substances which have the plasticizing effect on clay materials contain. On the example of natural clays of three various fields the plasticizing action melasses bards is proved, and the number of plasticity of the studied clays increases in direct ratio to increase in additive melassny bards in clay raw mix. It is shown that introduction to raw mix melasses bards leads to improvement of appearance of pottery, decrease in jointing, increase in durability for Veselovsky clay for 7%, for the Oryol clay for 67%, for Bessonovskaya – for 23%.
Research of the received ceramic samples on frost resistance according to requirements of GOST bards unlike the products which aren’t containing additive bards showed high frost resistance of products with additive melass. Also lowered decrease in durability and loss of mass of the samples containing additive melassny bards is noted.
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