Papers by Keyword: Aerated Concrete

Abstract: The possibility of using breakage of technical glass in conjunction with liquid glass to obtain aerated concrete by low-power technology is considered. The necessary strength is provided by finely ground unsorted breakage of technical glass with a specific surface area of 450, 500 and 550 m2/kg. The compressive strength of aerated concrete samples is 0.08; 0.25 and 1.8 MPa, and the bending strength is 0.04; 0.08 and 0.33 MPa, accordingly. The optimum is grinding to a specific surface area of 500-550 m2/kg, a finer grinding is irrational, because it does not lead to a significant increase in the surface of the particles. It is shown that the use of only finely ground cullet in the composition of aerated concrete is not effective, since the density of the samples increases with a significant decrease in strength due to the fragility of the interpore partitions. At the same time, thermal conductivity increases and the operating temperature range decreases to 400 °C, due to an increase in the fusibility of the material. It is necessary to reinforce the resulting partitions for the formation of a dense and durable structure. For this, it is proposed to use crushed cullet with particle size modulus 0.945. It has been experimentally established that the ratio between finely ground and crushed cullet should be in the range of 1.97 - 2.24. This ratio of components provides the necessary strength for aerated concrete based on liquid glass and unsorted broken technical glass. With an average density of aerated concrete in a dry state of 150 - 320 kg/m3, the compressive strength is might be up to 2.0 MPa and the bending strength is might be up to 0.38 MPa. The aerated concrete obtained in this work had a thermal conductivity coefficient of 0.05 – 0.09 W/(m°C), with an operating temperature range of-60 ... + 800 °C.

Abstract: This paper presents the results of developing a single-stage method to obtain effective structural and thermal insulation products based on cellular concrete with anisotropic structure and studies their properties. Methods to determine the start and end time of gas generation of the system, determine the emission value, determine the density change of anisotropic materials have been used in this study. The experiments show that ability to adjust the coefficient of variation for cellular concrete depends on the shape fill factor. The degree of variation increases from 2.22-2.86-3.33, increasing the load-carrying capacity of construction products with anisotropic structure than concrete with a one-dimensional cellular structure that consumes materials. In addition, products based on cellular concrete meet all the required criteria for strength, stiffness and frost resistance due to the high density of the surface layer.

Abstract: The experimental studies’results of the structure and properties of cellular concrete with one-stage preparation of foam concrete mixtures are presented. The effect of the filler on the foam concrete properties has been evaluated. The possibility of producing high-quality chalk foam concrete from soft crushed chalk with a fraction of 2.5 mm has been proven. The influence of the slip viscosity, the type and amount of the foaming agent, the type of cement on the properties of small foam concrete has been established.

Abstract: Today, the development of aluminium industry is highly dynamic. Aluminium production rightly takes top positions in the global metal market. Unique properties of aluminium mean that it is widely used in various industries. The construction industry is no exception – here, aluminium is actively used as a gassing agent for production of steam-cured aerated concrete, which is produced by mixing Portland cement, sand, water and aluminium fine powder or aluminium paste. The main disadvantage of aluminium fine powder is its high degree of dusting: at certain air concentration levels, this becomes fire-and explosion-prone. This is the reason the producers add complex organic additives into their aluminium fine powder: to ensure lower dusting levels and produce an aluminium paste, which is safer to use. This work focuses on obtaining an aluminium paste with sufficient share of organic additives to ensure the efficient performance of aluminium paste as a gassing agent in the production of steam-cured aerated concrete. A number of tests were carried out on mixing aluminium fine powder with various organic additives (fatty additive; wetting agent and gassing kinetics stabiliser; dedusting agent) in different ratios. The paper analyses the quality of distribution of organic additives inside the finished product and studies the relevant gassing kinetics.

Abstract: The efficiency of porous structure formation in aerated concrete can be improved by including the methods of thermal vacuum compaction or thermal vacuum compaction with vibration into the process as a means of creating high-quality composite cellular concrete. A graphic model of a phase composition change in the aerated concrete mix was developed allowing for an evaluation of the recipe and the mode of bubble porosity generation during hardening. This provides a control over the manufacturing processes and helps to produce aerated concrete with the specified porosity balance, which defines product properties.The effect of temperature and vacuum on molding sand during the initial stage of manufacture is proportional to the bubble porosity volume, which is important for a high-quality porous structure formation. In addition to the above, account must be taken of the combined effect of temperature, vacuum and volume ratio of phases in the base mix when using the proposed methods.Introduction of the developed processing methods into the manufacturing process improves the technology of aerated concrete production and allows for a fabrication of the finest advanced heat insulating and structural and heat insulating products.

Abstract: The possibility of using technical glasswork with liquid glass to produce aerated concrete using low-energy technology was considered in the paper. The unsorted technical glass cullet use as a part of aerated concrete will allow the non-decomposing industrial wastes disposal, which makes it possible to speak about the environmental technology development, while reducing the cost of producing effective heat-insulating materials considers its economic efficiency. The optimum liquid glass density was established upon aerated concrete mix receipt, which should be at least 1.23 and not more than 1.35 g / cm³. The technical characteristics of aerated concrete based on cullet and liquid glass obtained in this work are determined. Thermal conductivity of aerated concrete with its density of 150-400 kg / m³ is 0.06 W/m°C. The resulting aerated concrete is recommended for thermal insulation of pipelines both during construction and during their repair.

Abstract: The high water demand of finishing compositions obtained using expanded perlite and vermiculite sand reduces the crack resistance of the resulting thermal insulation coatings. The use of microspheres as fillers should make it possible to increase the crack resistance of the resulting coatings. The crack resistance of lime heat-insulating coatings for the finishing of aerated concrete obtained using ash microspheres of aluminosilicate and expanded vermiculite sand has been determined. It is established, that coatings obtained using aluminosilicate ash microspheres, are characterized by good crack resistance due to low shrinkage deformations, high ultimate tensile properties and uniform distribution of moisture content in the process of moistening.

Abstract: The aim of the research was verification of influence of aeration and influence of aluminum powder on microstructure and physical mechanical properties of calcium silicate composite material. At the same time, influence of various dosages of alternative raw materials on porous structure of the composite was examined. Tested raw materials are not the ones commonly used in the technology of manufacture of calcium silicate composites, for example chamotte blocks, Lining of silica and foundry sand. It was found that influence of aeration of calcium silicate composite causes reduction of compressive strength by roughly 85%. At the same time, volume weight drops by 50%. As a consequence of the expansion, intensity of diffraction lines of tobermorite detected by X-ray diffraction analysis is reduced because of reaction of aluminum powder with calcium hydroxide. It was found that there is dependency between the amount of replacement of silica sand with foundry sand and silica, and intensity of tobermorite diffraction lines, where the intensity of the diffraction lines was reduced with increased amount of replacement.

Abstract: Theoretical principles of the formation of highly organized porous structure of cellular concrete are developed, based on model concepts of the dynamics of the expanding gas cavity in the liquid phase as a single control cell. The peculiarities of controlling the formation of cellular structure of aerated concrete based on the balance of forces in a three-phase disperse system on the model "gas pore - molding mixture" are revealed and a coalescing-aggregate scheme for porosity formation of the aerated concrete mixture is proposed. It is shown that, in accordance with the refined Rayleigh-Plesset equation, the determining factor in the formation of the cellular structure of aerated concrete is the pressure over the mixture to be poroused, the effect of the porosity being achieved by reducing the external pressure to the vacuum level. The division of pores by size in anaerated concrete mixture is proposed. The maximum pore size is determined by the capillary Laplace constant. The prospects of aerated concrete technology are associated with a decrease in the maximum and average size of cellular pores, as well as methods for eliminating pores of air entrainment and segmented pores. Reducing of the size of the pores will be reflected in the decrease of the Bond quantity and in the increase of the importance of capillary forces in the formation of the porous structure of aerated concrete. The concepts of the types of cellular structures are developed, depending on the average density and their boundaries for cellular concrete are established.

Abstract: The main drawbacks of aerated concrete preparation traditional technology are considered. The method essence for the porous structure formation of aerated concrete products with variational properties is formulated. The main factors affecting aerated concrete products properties of varying density and strength along the cross-section are indicated. The mold cover closed surface with a circular opening area effect on aerated concrete products main properties is shown and its optimum value is revealed. The traditional and modern types gas generators influence on gas evolution kinetics, mixture swelling height, gas generators stability in time and variable density and strength on the cross-section aerated concrete products main properties are considered.