Cellular Concrete Products Research Articles

Influence of the W/S ratio on the cellular concrete properties on the basis of fly ash

The article considers the results of a study of fly ash from the Ekibastuz coal basin in the production of cellular concrete. Studies have shown that the composition of fly ash is very complex in terms of the variety of chemical elements and its use as a siliceous component instead of sand has a beneficial effect on the value of the W/S ratio. A study of the pore structure of cellular concrete showed that an increase in the W/S ratio leads to a sharp change in the nature of the porous structure, that is, the higher the W/S, the higher the quality of its porous structure. However, an excessive increase in W/S causes stratification of the solution. In order to establish the optimal value of the W/S ratio using fly ash, studies were carried out. The results of a study to determine the influence of the porous structure of cellular concrete on its properties clearly showed how, with increasing W/S ratio, the porosity deviation index decreases, and the lower the porosity deviation, the better the characteristics of the macropores of cellular concrete, and accordingly, the higher the strength of aerated concrete.

Алкилмен алмастырылған фенолдар негізіндегі түрлендіргіш қоспа

This article explores the utilization of mixtures in the production of cellular concrete, leveraging alkyl-substituting phenols to attenuate the wetting impact of cement. Incorporating alkyl-substituting phenols enables the preservation of cement with low alkali and aluminum content for extended durations compared to those with higher levels of tricalcium and alkali additives. Investigation into the heat release patterns during the wetting of various cements revealed additional alternative effects: high alkali content cements diminish calcium impurities in aqueous acid within the liquid phase, while high aluminum content cements exhibit reduced moistening of aluminates. Both of these alternative effects collectively demonstrate that tricalcium aluminates and tricalcium silicates mitigate the influence of humectant carbonate acid on the hydration process.

Влияние технологических факторов на плотность и прочность зологазобетона

One of the promising areas of fly ash utilization is the production of cellular concretes. The experience of using cellular concrete products in construction has shown that they can successfully compete with most traditional materials combining high thermal insulation and structural properties. The paper examines the influence of technological factors: grinding, composition, water temperature and water solid ratio on the density and strength of the gas and gold cement. Purpose of the study. Determination of the influence of technological factors of production on the density and strength of ash gas concrete. Materials and methods. Portland cement, fly ash from Ekibastuz GRES-2, bassanite, and aluminum powder were used as starting materials. The composition of ash gas concrete with an average density of 700, 800 and 900 kg/m3 was developed according to the technical requirements of CH 277-80 – Instructions for the manufacture of cellular concrete products. The physical and mechanical properties of cellular concrete were determined in accordance with the technical requirements of the current standards. The result s and discussion. On the basis of the basic composition, the influence of technological factors on the density and strength of ash gas concrete has been studied. As a result of the research, it was found that the strength of samples with an average density of 700 kg/m3 reaches 3.5 MPa, and with an average density of 800 and 900 kg/m3 – 5.1 and 7.6 MPa, respectively. These indicators confirm that the samples obtained from mechanically activated gold cement binder according to the technical requirements of GOST 25485-2019 correspond to the structural and thermal insulation properties of cellular concrete. Resume. The physical and technical properties of raw materials, concrete mixtures and cellular concretes were studied using Ekibastuz GRES-2 ash as a fine filler. The study showed that production technological factors such as the dispersion and composition of the mixture, the water-solid ratio and the temperature of the mixing water have a significant effect on the density and strength of the ash gas concrete. Optimization of these parameters makes it possible to achieve the specified values of density and strength in the resulting material. Proposals for practical application and direction of future research. The possibility and expediency of using the ash of Ekibastuz GRES-2 as an additive in the manufacture of ash gas concrete has been established.

Кремнийлі компоненттер мен олардың газдалған бетон түрлеріне әсерін зерттеу

The article discusses the results of a study on the utilization of fly ash from thermal power plants as a silica component and its impact on the properties of aerated concrete. The primary objectives of contemporary construction endeavors include energy conservation, enhancement of building material quality, and durability. This issue can potentially be addressed by advancing the production of cellular concrete through the utilization of fly ash sourced from thermal power plants.

Жылу электр станцияларында (ЖЭС) ұшқынкүлін ұялы бетонды өндірісінде пайдалану

This use of fly ash from thermal power plants (TPPs) as a silica component in the production of cellular concrete is considered. The use of fly ash from thermal power plants (TPPs), due to its fine-grained composition, reduces energy costs for grinding and solves important national economic problems, in particular, issues of improving the maximum environmental situation in the region through the disposal of large-tonnage waste and environmental protection. The most effective use of superplasticizers increases the physical and mechanical composition of cellular concrete. When using complex mixtures based on superplasticizers in the production of cellular concrete, it is possible to obtain autoclaved aerated concrete with high physical and mechanical properties. Nowadays, prices for chemical mixtures have increased, and they are becoming economically unprofitable for the production of cellular concrete, so the use of fly ash from thermal power plants as a substitute is more rational. In addition, using the autoclave hardening method, it is possible to increase the physical and mechanical properties of cellular concrete and reduce the weight of elements at a specific cost of materials.

Optimization of Cellular Concrete Formulation with Aluminum Waste and Mineral Additions

The paper aims to study cellular concrete with a new approach of formulation without an autoclave, with the use of aluminum waste and incorporation of mineral additions into the sand and evaluate its physical and mechanical properties. In this experimental study, two types of cellular concrete are prepared, based on crushed and dune sand with the incorporation of 15% of the slag and 10% of pozzolana, as sand replacement. An experimental program was performed to determine the compressive strength at 28 days, the density and thermal conductivity of the confected cellular concrete. The obtained results showed that concretes prepared with crushed sand developed better mechanical resistance compared to the dune sand. It is also noted that the concretes containing the mineral additions provide a substantial increase in compressive strength in particular slag. Furthermore, cellular concretes with sand dunes offer better thermal conductivity, compared to those with crushed sand. The use of the additions reduces the Water/Binder (W/B) ratio and leads to a lower thermal conductivity regardless of the used sand nature. The outcome of the present study here in could present a modest contribution for the production of cellular concrete with local materials in particular dune sand, active mineral addition and aluminum waste. The physical and mechanical properties obtained from this new composition are estimated acceptable compared to those of the industry-prepared cellular concrete product. Doi: 10.28991/cej-2021-03091721 Full Text: PDF

The effect of lime on the quality of cellular concrete products

The effect of lime on the quality of cellular concrete products

Energy-efficient double-row masonry of the exterior walls in the buildings made of cellular concrete blocks

Ensuring the increased requirements for heat saving, environmental safety and comfort of residential and public buildings is one of the main directions of scientific and technological progress in construction. In particular, the cellular concrete products’ use in building envelopes is aimed at solving these problems. Cellular concrete blocks perform the wall-forming material functions and insulation simultaneously due to their thermophysical and strength characteristics. However, the factor reducing the energy efficiency of aerated concrete masonry is the filling of masonry joints with adhesive or cement-sand mortar, which are the thermometer bridges, and the use of polyurethane adhesive, which has lower thermal conductivity compared to adhesive mixtures, as an aggregate of vertical and horizontal joints is unacceptable due to its high deformability and low shear stiffness. The authors examined the systems of building envelopes made of cellular concrete blocks used in civil engineering, and identified their shortcomings that affect the energy efficiency of the entire building. The authors have developed an energy-efficient two-row masonry of cellular concrete blocks, the device of which allows to reduce the masonry thickness and facilitate the installation of the enclosing structure with equal masonry thermal conductivity.

Foam fiber-reinforced concrete: technology and methodology of selection of the composition

Disperse reinforcement of the mineral matrix in concrete technology makes it possible to manufacture structures of complex configuration, to solve problems of frost-resistance of products, minimize shrinkage deformations. The technologies of application of dispersed reinforcement of a concrete matrix with the help of synthetic, mineral and metal fibers has been developed. Perspective is considered reinforcement with basalt fiber - material resistant in alkaline environments of cement stone and having high adhesion to the mineral matrix. Foam concrete in industrial conditions is produced either in a one-stage or two-stage scheme. The technology of foam concrete of two-stage manufacturing has been studied quite well and its formulations have passed a wide approbation. The novelty of the research is the integration of basalt fibers into the concrete mix as a dispersive reinforcing component. This aspect has been given special attention in research. It is established that the consumption of basalt fiber affects both strength and density of cellular concrete products. The length of basalt fiber affects only the strength of products. As a result of the system analysis of penofibrobeton technology using the methodology of mathematical planning of a multifactorial experiment, obtaining results based on statistical analysis and optimizing these results, a mathematical model has been built and a technique has been developed of selecting of the composition penofibrobeton in densities from 400 to 600 kg/m3.

One-part eco-cellular concrete for the precast industry: Functional features and life cycle assessment

This paper focuses on investigating greener alternatives of cellular concrete technology to fulfil current searches for a shift to circular economy. A novel one-part eco-cellular concrete (ECC-OP) was developed and studied. The one-part alkali activated materials (AAM-OP) and new alkali-activated cellular concrete (AACC) technologies were combined to develop greener alternative of cellular concrete production. The progressive steps from traditional cellular concrete (TCC) based on ordinary Portland cement (OPC) and commercial aluminium powder (A) to a 100% waste-based cellular concrete are presented. Blast furnace slag (BFS) was the precursor, RHA was employed as the silica source, olive stone biomass ash (OBA) was the alkali source and recycled aluminium foil (AR) was employed as an aerating agent. The functional features of the materials were studied and compared to those established by the European standard and the American Concrete Institute (ACI) Committee 523 guides. The new ECC-OP with a bulk density, compressive strength and thermal conductivity that respectively equal 660 kg/m3, 6.3 MPa and 0.20 W/mK was obtained. Finally, a cradle-to-gate life cycle assessment (LCA) was made, where the industrial process of a masonry unit manufacture was raised by using each studied material. A 96% reduction in the kgCO2eq per m3 of material was reached with the new proposed ECC-OP compared to TCC manufacturing.

Modeling the process of autoclaving treatment of cellular concrete products as control object

The authors consider the questions of modeling the process of autoclave treatment of cellular concrete products as a control object. The modeling method, performed in several stages, is suggested. At the first stage, a mathematical model of energy processes occurring in an autoclave, taking into account the internal heat generation during the formation of tobermorite in raw cellular concretes, is developed. The temperature dynamics of steam in an autoclave T n (t) has been determined. At the second stage, heat transfer in a cellular concrete is modeled for a given value of T n (t). As a result of computational experiments, the temperature dynamics T m (x, y, z, t) in the most characteristic parts of the cellular concrete was determined. The assessment of the adequacy of the developed model was made by comparing the results of modeling with the results of experimental studies obtained with the existing process equipment.

Low energy compositions based on inorganic binders

The results of scientific research in realization of energy-intensity cellular concrete production technology of normal condition hardening are shown. Physical-mechanical and thermophysical properties of cellular concretes, which are produced by this technology, are relevant to active normative documents. In this case the produced cellular concretes are characterized with strength increasing in time in compare to autoclave hardening cellular concretes and aerated concrete. The influence of the chemical activity of the fillers on the performance of the final product has been established.
 According to the results of the performed researches it is established that the activity of the filler determines the kinetics of change in the time of the strength of the composition, which solidifies under normal conditions. When used as ground coal ash filler, the level of strength of porous concrete at the age of 28 days is at the level of strength of the composition with the addition of ground granulated slag (3,22 and 3,38 MPa, respectively).
 It is also found that, unlike autoclaved aerated concretes, the strength of aerated concretes of normal cement based on Portland cement increases over time both on binder without mineral additives and in the presence of ash, milled slag and quartz sand. The intensity of the process of gaining strength over time is determined by the activity of the mineral additive. When used as a mineral admixture of non-ground quartz sand, which, under normal curing conditions, does not interact with the curing of Portland cement, the strength of the porous concrete decreases with increasing amount of this additive in the composition. The intensity of the strength of these compositions at the age of 90 days, depending on the amount of additive, is 10 - 18%.
 The proposed technology for the production of cellular concrete based on Portland cement, curing under normal conditions, was implemented in industrial production. D700 concrete was selected as the base for production.

ТЕХНОЛОГИИ ПОЛУЧЕНИЯ МНОГОСЛОЙНЫХ КОНСТРУКЦИЙ ВАРИАТРОПНОЙ СТРУКТУРЫ

The current state of the market for the production of aerated concrete in the Russian Federation and its prospects are considered. Every year, the production of cellular concrete is constantly increasing due to the construction of new plants that produce the most advanced technologies with the use of modernized equipment. However, there are technological and prescription raw materials issues. Therefore, the development of new technologies for the production of cellular concrete products due to the improvement, modernization and development of fundamentally new technological methods is highly important. The technologies for producing multilayer cellular concrete designs with a variational structure are considered. This allows to get products with high performance that meets modern requirements for energy efficiency and durability. The method of layered pouring of a cellular concrete mixture into a form with removable partitions is proposed for creating a single-layer construction of cellular concrete with variable density over the section. The integral principle is shown from small ones at the periphery, to large ones in the middle of the block, taking into account the rheological characteristics of cellular concrete mixtures and the foaming time. They provide the possibility of obtaining a design with a smooth transition of the structural heat-insulating layer to the layer without seams, air gaps and other possible defects arising during the molding of three-layer structures from non-uniform materials.

Теплотехнічні особливості будівництва та експлуатації газобетонних зовнішніх стін малоповерхових будівель

There have been investigated the state and structure of constructing the residential buildings. The research of the modern state and structure of residential buildings showed that in Ukraine, by analogy with the developed countries of the world, specific gravity of residential building grows. The dynamics of production of cellular concrete is presented, as a modern energy effective wall material. The basic tendencies of perfection of quality and improvement of operating descriptions of autoclave cellular concrete are exposed. Modern approaches of estimation of heat conductivity of cellular concrete wares are shown depending on its humidity. There has been presented the information on improving the regulatory framework of constructing. The estimation of heating engineering features of energy effective outward cellular concrete walls of residential buildings is carried out. Principal reasons for the negative consequences of the use of cellular concrete are exposed in the non-load-bearing constructions of buildings. There have been exposed basic technological features of storage of cellular concrete, building process and its exploitation in wall constructions, especially in the first years of exploitation of building. Classification and basic physical and mechanical parameters of cellular concrete are presented on kinds and terms of hardening. It is noticed that the self-weighted humidity of building wall is gained during 2—3 years of its exploitation. Modern approaches of prognostication and empirical regularities of heat conductivity of cellular concrete are analyzed depending on its humidity. There have been defined the basic approaches and recommendation on providing the efficiency of the use of cellular concrete in the non-load-bearing constructions of residential buildings.

The use of steel cylindrical nuggets for joints of combined foam concrete elements

In our time, cellular concrete products are becoming increasingly widespread in building practice. The most common types of such concrete are foam and aerated concrete. Foam concrete, as a constructive material, plays a significant role in saving money spent on the operation of buildings. Such savings can be achieved at the expense of a fairly low thermal conductivity of foam concrete. Due to the positive properties of foam concrete, it can be used effectively enough as a material for supporting structures, not only homogeneous, but also in combination with other materials. Therefore, in some cases, it is necessary to connect individual elements of the construction, which is made of different materials, one of which is foam concrete. The connection in this case should be simple to execute and reliable in operation. In the article the variant of connection of a foam concrete linear element with wooden by the simplest means for unification - steel cylindrical nuggets is considered. In the process of the experiment, three types of clogging of nails were adopted in the thickness of foam concrete. In addition, for each type of clamping, five variants of placement of metal cylindrical nuggets by the length of connection of the foam concrete element with wooden ones were used. The diameter of the nuggets was the same. The experiment allowed to trace the nature of the destruction of prototype samples for all variants. Since today there are no methods for calculating such compounds, for the theoretical determination of bearing capacity techniques have been adopted relating to the connection of wooden elements. Some assumptions are made and recommendations are given on the application of each proposed type of joints with cylindrical nuggets of foam concrete and wooden elements.

Complex Researches in the Field of Creation of Crack-Resistant Wall Panels from Cellular Concrete with Prestressed Reinforcement

The investigations carried out in the field of creation of large-size crack-resistant structures and cellular concrete products have shown that this problem is multifaceted and it must be solved in a complex manner, and one of the ways to increase the crack resistance and durability of such structures and products is prestressed reinforcement.

Technological Processes for Manufacturing Cellular Concrete Products for Construction

Cellular concrete occupies one of the leading places in world practice of a high-rise construction as the constructional heat-insulating material used in case of construction and reconstruction of buildings and constructions of different purpose. In this artificial stone construction material pores (air cells with diameter 0.1-3.0mm) are distributed rather regularly and occupy from 20 to 90% of amount of concrete, providing high heatphysical qualities (coefficient of heat conductivity of 0.07-0.2 W/ms) that allows cellular concrete houses to keep heat well. Excessive (reserve) porosity of cellular concrete provides its frost resistance (compensates expansion of water when freezing and the formed ice without material destruction). Vapor permeability of cellular concrete provides fast removal of technological moisture from material and maintenance of normal moisture conditions in rooms, and rather high air permeability promotes preserving in rooms of fresh air. Significant growth in production the cellular concrete of products is caused by use of rather simple technologies allowing (due to change of degree of porosity and properties of interstitial material) to receive cellular concrete for thermal insulation or sound insulation, to make wall constructional heat-insulating products with a density 250-1200 kg/ m3 and strength of a 1-25 MPa.

Ash Deposits CHP – as an Additional Source of Raw Material for Construction Production

Issues related to the rational processing of industrial waste and the protection of the environment are of particular importance. The prerequisite for writing this article was the ecological situation in Kazakhstan. Currently, many industrial enterprises have accumulated and continue to accumulate man-caused waste of production processes that not only pollute the atmosphere and, washed away by rain and snow, pollute the water basin of nearby areas. The work of CHP is one of the main polluters of the environment, mainly the air basin. CHP plants operating on traditional types of fuel contribute up to 30 % of the volume of harmful emissions of the atmosphere, pollute the land and water with combustion products and sewage. Technogenic wastes occupy hundreds of thousands of hectares of fertile land. In them, the content of non-ferrous metals reaches up to 5 %, iron up to 45 %, in addition, some of them contain noble metals. The bulk of this waste is siliceous materials, which are the main source of building materials. In Kazakhstan, as yet, they have not been engaged in the utilization of ash, these are technogenic waste from the thermal power station. Known methods of processing such raw materials do not fully comply with modern requirements of scientific and technological progress. Dumps of ash and slag materials occupy large areas, and their content requires significant operating costs, which affect the increase in the cost of production of energy. They are a source of environmental pollution, present a danger to public health and a threat to the plant and animal life of the surrounding areas. Especially dangerous are ash dumps located near water basins (rivers and lakes), because of the possible breakthrough of dams. Effective utilization of coal energy coal plants can help significantly reduce the negative impact on the environment and improve the economic performance of the enterprise. In general, ash is widely used in various industries and has good market prospects. There are available technologies for ash utilization, some of which are widely used commercially. At present, the main quantity of ash is used in the construction industry - this is the production of cement, bricks, cellular concrete products, slag blocks, lightweight aggregates, roofing material, expanded clay, construction of dams for ash dumps, construction and repair of roads. The use of ashes and slags of CHP as building materials is the most ambitious direction and can solve the problem of building materials shortage in the regions of Kazakhstan in the future. Due to the use of ash waste, we can save up to 30 % of cement and more than 50 % of natural aggregates, thereby reducing the thermal conductivity of concrete will reduce the mass of buildings and structures. To attract investments in order to increase the level of processing and use of ash waste, it is possible to use interest in the purchase of ash and slag from the thermal power stations of Kazakhstan in those Western European countries and the Middle East, where there are not enough sources of mineral raw materials in sufficient quantities. The solution of the above problems is necessary to increase the level of utilization of ash waste with a view to reducing their accumulation, improving the environmental situation in the vicinity of the CHP plant, as well as receiving income from the sale of products produced on the basis of ash waste.

Investigation of activated aluminum as a component of cellular concrete with complex porosation

In this paper indicators of the quality of activated aluminum, proposed for use as a poreforming agent in the production of cellular concrete with complex porisation are presented. The efficiency of ultrasonic homogenization of the poreforning agent in the presence of a mineral modifier of cellular concrete which provides high stability of the suspension in time is substantiated.

Manufacturing processes of cellular concrete products for the construction

Cellular concrete takes the lead in the world of construction as a structural insulation material used in the construction and reconstruction of buildings and constructions of various purposes. In this artificial stone building material, pores are distributed relatively evenly and occupy from 20 to 90% of the concrete volume, ensuring good thermal qualities, which allows cellular concrete houses to keep warmth well. For production of cellular concrete, Portland cement, “burnt lime”, and fine-pulverized blast furnace slags, with a hardening activator are used as binders. As silica components, quartz sand or “fly ash” obtained by combustion of pulverized fuel in power plants as well as secondary products of different ore dressing treatments are used. The low density and high thermal insulation properties of cellular concrete enables 3 times lighter wall weight than the weight of brick walls and 1.7 times lighter than the walls of ceramsite concrete. Thermal insulation and mechanical properties of cellular concrete make possible to construct of it single-layer protecting structures with the desired thermal resistance. Cellular concrete is divided into aerated concretes and foam concretes, whose physical/mechanical and operational performance is, ceteris paribus, almost identical. By the method of hydrothermal treatment cellular concretes are divided into two groups: concrete of autoclave and non-autoclave curing.