Raw Mixture Research Articles

Aluminum waste in alumina cement production (Mikhailovka)

Alumina cement is a rapidly hardening hydraulic binder containing low-basic calcium aluminates in the final product. The alumina cement production by melting is widespread. Melting of the mixture consisting of bauxite and limestone is carried out in the temperature range of 1500 to 1600 °C, which entails enormous energy consumption and, accordingly, the higher cost of resulting products. The paper studies the possibility of reducing the melting point as well as the cost of the main mixture component bauxite via its replacement by aluminum-containing waste.Purpose: Suggest the dependence between the mixture composition and the Al2O3 content in the initial aluminum waste; determine the best annealing temperature for alumina clinker; study strength properties of the resulting alumina cement and the effect of introduced limestone on the main quality index.Methodology: The chemical composition of the aluminum waste (sludge and powder), raw mixtures, and resulting clinker are detected in laboratory conditions using spectrophotometry and flame photometry methods in accordance with the state standard. X-ray phase analysis of waste and clinker is based on the powder diffraction method and conducted on the Thermo Scientific ARL X'TRA Powder Diffractometer. Physical and mechanical tests are carried out in accordance with the state standard poly-fraction sand.Research findings: Laboratory studies show that aluminum waste (sludge and powder), consisting of gibbsite and boehmite in combination with limestone, is suitable for the production of alumina clinker. Depending on the initial Al2O3 content, their content in the raw mixture ranges from 60 to 75 %.Value: Depending on the composition, the fest annealing temperature for alumina clinker, is 1350 to 1400 ℃; the mineralogical composition of clinkers consists of 85–90 % calcium aluminates. Alumina cement strength determined in small test samples having normal density and the ratio 1:0, is high after 2 days and ranges from 33.7 to 40.6 MPa. The addition of 5 % crystalline limestone into cement accelerates the initial rate of hardening and improves the strength from 33.7 to 53.2 MPa after 2 days due to the additional formation of 3CaO·Al2O3·CaCO3·11H2O.

Formation of Cellular Concrete Structures Based on Waste Glass and Liquid Glass

The use of waste in the production of building materials is one of the possible ways to solve problems related to the sustainable management of non-degradable waste and difficult-to-recycle secondary resources. In this paper, a method is proposed for the non-autoclave production of an ultra-lightweight cellular concrete based on Portland cement, glass waste and liquid glass. A mixture of sodium hexafluorosilicate and hydroxide is used as a hardening activator, an aluminum powder serves as a gas-forming agent. The setting and hardening of raw mixtures occurs under the action of exothermal heat release due to a complex of chemical reactions occurring in the system, and the resulting material does not require additional heat treatment. It is optimal to use two fractions of glass waste to achieve acceptable material strength: coarse crushed (fineness modulus Fm = 0.945) and finely ground (specific surface Ssp = 450–550 m2/kg) glass. Glass particles of the fine fraction of glass, along with Portland cement, participate in hydrolytic and structure-forming processes, while glass particles of the coarse fraction play the role of reinforcing filler. The influence of the dispersion of glass and the density of liquid glass on the density, porosity, strength, water absorption and water resistance of the resulting cellular material was determined. At an average density of cellular concrete in the dry state of 150–320 kg/m3, the following characteristics can be achieved: a compressive strength up to 2.0 MPa, bending strength up to 0.38 MPa, thermal conductivity coefficient of the material in the range 0.05–0.09 W/(K·m), and a maximum operating temperature of 800 °C. The proposed ultra-lightweight cellular concrete can be used as a non-combustible heat and sound insulation material, as well as a repairing composition; the cellular concrete blocks can be used as filling masonry and for the construction of non-bearing internal walls.

Microwave-assisted hydrothermal synthesis of autoclaved bricks from municipal solid waste incineration fly ash and coal fly ash (MSWIFA) and its carbon emission

In this study, the feasibility of manufacturing low-carbon autoclaved municipal solid waste incineration fly ash and coal fly ash (MSWI-FA) bricks from MSWI fly ash and coal FA with microwave-assisted hydrothermal synthesis was investigated. To facilitate the experiment, block samples were prepared. The effects of microwave pre-treating parameters on the performance of block samples were investigated. Mechanisms of microwave pre-treating were studied. The effects of microwave pre-treating were further investigated by micro-analyses of synthesized block samples. Environmental impacts were discussed from heavy metal solidification/stabilization and CO2 emission. The results showed that the optimal microwave parameters were 30 min and 385 W. With microwave pre-treating, Al-substituted tobermorite crystallites were generated in raw material mixtures. For block samples, more Al-substituted tobermorite crystals were observed, and lower total pore volume and pore diameter were found. The solidification/stabilization rates of Cu, Pb, and Zn increased by 163.20%, 24.89%, and 78.77%, respectively, and CO2 emission could be reduced up to 53.40%.

Making high-performance Al2O3-3YSZ ceramics with eutectic/polycrystalline structure by hot-pressing eutectic powders

In this communication, the Al2O3-3YSZ ceramic (AYC) was prepared by hot-pressing the eutectic powders. A continuous transition from raw powders mixture to synthesized eutectic powders to sintered eutectic bulk was traced and investigated. The AYC well preserves the structure and phase composition of the original Al2O3-3YSZ eutectic powders (AYEP), which possess a eutectic/polycrystalline composite structure. The average interphase spacing of eutectic region in AYC reaches 106 nm. The strength, toughness, and hardness of AYC specimen are as high as 768 ± 23 MPa, 8.17 ± 0.30 MPa m1/2, and 19.04 ± 0.45 GPa, which far surpasses other solidified and sintered Al2O3-based eutectic ceramics. The excellent mechanical properties can be attributed to the synergistic toughening mechanisms of intergranular/transgranular fracture, t-m phase transformation and residual stress. These results clearly demonstrate the feasibility of sintering eutectic powders method to fabricate Al2O3-based eutectic ceramics concurrent with fine structure and large dimension.

Fused Filament Fabrication for Metallic Materials: A Brief Review.

Fused filament fabrication (FFF) is an extrusion-based additive manufacturing (AM) technology mostly used to produce thermoplastic parts. However, producing metallic or ceramic parts by FFF is also a sintered-based AM process. FFF for metallic parts can be divided into five steps: (1) raw material selection and feedstock mixture (including palletization), (2) filament production (extrusion), (3) production of AM components using the filament extrusion process, (4) debinding, and (5) sintering. These steps are interrelated, where the parameters interact with the others and have a key role in the integrity and quality of the final metallic parts. FFF can produce high-accuracy and complex metallic parts, potentially revolutionizing the manufacturing industry and taking AM components to a new level. In the FFF technology for metallic materials, material compatibility, production quality, and cost-effectiveness are the challenges to overcome to make it more competitive compared to other AM technologies, like the laser processes. This review provides a comprehensive overview of the recent developments in FFF for metallic materials, including the metals and binders used, the challenges faced, potential applications, and the impact of FFF on the manufacturing (prototyping and end parts), design freedom, customization, sustainability, supply chain, among others.

First Proteome Analysis of Poplar-Type Propolis.

Propolis is a natural mixture of honeybee-released and plant-derived compounds produced by honeybees. Poplar propolis is rich in bioactive polyphenolic compounds, and due to its many health benefits, it is commonly used as a food supplement or functional food ingredient. However, it is the only honeybee product whose proteome hasn't been analyzed. Here, we report a first proteome analysis of poplar-type propolis, a challenging glue-type resinous sample for protein characterization. Raw propolis mixture was precipitated with cold acetone to obtain the protein fraction. Proteins were digested with trypsin, and generated peptides were analyzed on nano-ESI-qTOF SYNAPT G2-Si mass spectrometer (MS) by data-independent acquisition (DIA) and data-dependent acquisition (DDA). Identified peptides and inferred proteins suggest the presence of new bioactive molecules as components of propolis. The poplar-type propolis proteome is composed of a mixture of proteins from the Apis and Populus genera. This is the first-ever report of the proteome of any type of propolis.

Phase formation and hydration of alumina cements on the basis of cobalt‐molybdenum‐containing waste

AbstractThe subject of the research is features of synthesis of alumina cements on the basis of compositions of system CaO – CoO – Al2O3 – MoO3 with use of cobalt‐molybdenum‐containing waste for reception of refractory materials with a complex of the set properties. The processes of phase formation in raw mixtures have been investigated. X‐ray phase studies of clinkers fired at different temperatures and holding times proved that as a result of the interaction of the raw materials of the mixture in the material synthesizes a mixture of hydraulically active calcium mono‐ and di‐aluminate and refractory cobalt spinel, which provides the resulting complex high strength, accelerated curing time, fire resistance. The absence of phases corresponding to molybdenum compounds is explained by the fact that they are part of hydraulically active aluminates as limited solid solutions, deforming the crystal lattice and increasing hydraulic activity. Thus, it was found that the high strength of cement is due to the presence of calcium hydroaluminates such as C2AH8, aluminum hydroxide, as well as unhydrated grains of calcium aluminates, which will contribute to further long‐term strength. It is this coexistence of phases in both the crystalline and colloidal states provide high strength cement stone.

Quality of paving blocks soaking water made from medical waste incineration ash

Given the ash level of medical waste incineration utilized as a raw material mixture that contains metal compounds, dumping the paving block immersion water into rivers could result in a drop in water quality. The purpose of this study is to evaluate water quality during immersion of paving blocks made from medical waste incineration ash. Water quality was measured by five measurements in water before immersion, soaking for 7 days, 14 days, 21 days, and 28 days. The test method used is in accordance with SNI 6989-84:2019. The metal compounds examined in this study were Pb (lead), Copper (Cu), Nickel (Ni), and cadmium (Cd). Laboratory tests were conducted at the Jasa Tirta I Environmental Laboratory and the Sukoharjo Environmental Service. It can be concluded that there is no pollution due to heavy metals contained in paving blocks. The results show that the soaking water for 7 to 28 days is still below the specified quality, so paving block-making activities using a mixture of medical waste incineration ashes can be carried out. The need for other studies measuring the levels of other metals such as Cr, Hg, Sn, Ti, and Zn.

Characteristics of marine organic waste compost using Brunauer-Emmet-Teller, Fourier Transform Infrared, and Scanning Electron Microscope-Energy Dispersive X-Ray

On the basis of their composition, organic waste and inorganic waste may be differentiated from marine debris. Microorganisms have the ability to break down organic waste, hence marine organic waste can be bio-converted into compost. The goal of analyzing the properties of compost from marine organic waste was to characterize the organic components with FTIR, identify the surface area, pore diameter, and total pore volume of the compost, and evaluate the microstructure with SEM. The result with BET that marine organic waste compost has a surface area of 22.690 m2/g that has the potential for greater adsorption capacity. FTIR test show that chemical content in marine organic waste compost included 15 types of vibration with different wavenumber and %transmittance. The results of the SEM-EDX test for organic waste compost have that the main components of marine organic waste compost are Carbon, Oxygen, Magnesium, Aluminium, Silicate, Potassium, Calcium and Iron. The morphological structure of the SEM compost 1000x includes the structure of a very dense raw material mixture and herds, with 2500x; 5000x and 10000x cover a granular, porous, and fragmented structure which means that there is more space pore in the compost which is good as an adsorbent.

Hydration mechanism of special‐purpose cements

AbstractDuring baking of the raw mixture, a weak crystallization of hydraulically inert compounds is observed for these materials, providing a substrate for the growth of hydraulic compound crystals with limited solid solutions. As a result of grinding, cleavage of crystals will occur along the growth steps and intercrystalline boundaries, creating additional mechanical stress concentrators, which provides an increase in hydraulic activity. It appears that the full destruction of solid solutions does not occur, which results in strength enhancement of resulting hardened cement stone. The electron defects can also occur, having the form of deviations from distribution of electric charge corresponding to the regular structure of crystals. Upon hydration of the cements obtained from clinkers, highly basic hydrated newgrowths and active hydroxides are formed. At the same time, some leaching occurs on the surface of hydraulically inert compound resulting in a gelatinous hydroxide. With the lapse of time, gelatinous hydrate newgrowths transform to a crystalline state with decrease of basicity and lattice rearrangement into a more closely packed one. Amorphous hydroxides undergo crystalline aging and form a compactive crystallization frame around the grains of alkaline‐earth hydroaluminates.

Use of natural material (flask) of the Taskalinsky deposit of the West Kazakhstan region to obtain thermal insulation material

Modern construction market is experiencing a shortage of highly efficient thermal insulation materials. Alkali-silicate raw mixtures in combination with high-performance fillers currently make it possible to create porous heat-insulating materials with unique properties: rigid cellular structure, specified geometric dimensions and shape, low thermal conductivity, incombustibility, high processability, environmental friendliness, etc. at a relatively low cost. The use of such heat-insulating materials in construction allows solving the problems of energy saving, accessibility and cost-effectiveness. The article considers possibility of obtaining heat-insulating material based on sodium silicate (silicate glue "Polipax") and natural material - flasks from Taskalinsky deposit of West Kazakhstan region. Technical characteristics of Polypax glue are given. Using a scanning electron microscope, elemental, chemical, and oxide compositions of the flask were studied. A recipe for a heat-insulating composite material (HCM) has been compiled.To assess the quality of the obtained HCM, its physical and mechanical characteristics were determined: density, water resistance, thermal conductivity, strength. Samples I-II in terms of density and strength showed the best results, and samples III-IV differ slightly from the technical conditions in terms of the studied indicators. It has been determined that the obtained HCM using flask as filler has a positive effect on the performance properties of the heat-insulating material, and is also economically viable, because local raw materials are used. Thus, it is possible to use flask from Taskalinsky deposit of West Kazakhstan region as filler for heat-insulating material.

Technology and Peculiarities of Production of Large-format Ceramic Stones Based on Opoka-like Rocks

Introduction. One of the urgent tasks of the wall ceramics industry at present is the production of large-format ceramic stones with compressive strength of 10–15 MPa and thermal conductivity less than 0.12 W/(m·оС), while the market cost per 1 m3 should be competitive with gas-concrete blocks and be in the range of 5–6 thousand rubles per 1 m3. This problem can be solved by developing modern energy-efficient production technology and using opoko-like rocks and coal processing wastes as the main raw material as fuel and burnout additive.Materials and Methods. The opoka-like rocks — opokas from the deposits of southern Russia — Nagolnovskoye, Bakanskoye, Shakhtinskoye, Avilo-Fyodorovskoye, and coal cake produced by Pyramida LLC were used for research. The study of chemical and mineral composition was carried out by standard methods on prepared samples. The study of ceramic and technological properties (plasticity, molding moisture, degree of crushing, air and fire shrinkage, compressive strength, water absorption) of raw materials was carried out according to generally accepted methods on samples precrushed to a certain grain composition, since opokas, depending on the type, do not soak or slowly soak in water.Results. Pre-firing technological properties of opokas and their differences from traditional clay raw materials soaked in water were confirmed: increased molding moisture, small air shrinkage, low sensitivity to drying. The dependence of density and strength of samples on the degree of pulverization of opoka, firing temperature and the amount of carbon cake in the raw material mixture has been established. The influence of coal preparation wastes and their optimal amount on physical and mechanical properties of fired samples has been determined. The introduction of carbon cake allows to exclude the use of gas for firing or minimize its introduction. On the basis of the obtained results a simplified technological scheme for the production of large-format stones with minimum production cost has been developed.Discussion and Conclusion. The proposed technological scheme consists of two units of the main mass preparation equipment, molding of products is carried out by semi-rigid extrusion, drying of products is carried out directly on kiln cars, and for firing coal cake is used, which is introduced into the raw mix. These factors and technological methods allow to obtain products with low thermal conductivity, but with strength 3–5 times higher than that of aerated concrete blocks of similar density. The prime cost of ceramic stones will amount to 3–3.5 thousand rubles per 1 m3 of products. Rostov region, possessing opoka-like rocks and unclaimed reserves of technogenic coal raw materials, can become a center of production of large-format ceramic stones with low cost and provide the south and central part of the country with highquality wall materials.

Preparation of Spinel-Type Black Pigments Using Microwave-Assisted Calcination of Stainless Steel Dust: The Effect of Manganese Molar Content

Stainless steel dust is rich in valuable metal elements including Fe, Cr, Ni and Mn, which can be utilized to prepare Fe–Cr–Ni–Mn series black pigments. Meanwhile, manganese can absorb the majority of the visible light wavelength range, which improves the color rendering performance of Fe–Cr–Ni–Mn series black pigments. However, the coloring mechanism of manganese in the above black pigments is not clear. Therefore, the effect of manganese oxide content on the preparation of spinel-type black pigments from microwave-assisted calcination of stainless steel dust was studied in this work. The results show that with the increase in MnO content in the raw mixture, the crystal plane spacing of black pigments increases from 0.2525 nm to 0.2535 nm, the grain size grows from 61.4619 nm to 79.7171 nm, and the lattice constant grows from 0.8377 to 0.8406 nm. Moreover, the band gap is decreased from 1.483 eV to 1.244 eV, the absorbance increases significantly and has a consistent absorbance in the visible range, and the L*, a* and b* values reduce from 41.8, 0.6, 1.6 to 32.0, 1.0, 0.8, respectively. MnO can react with the spinel in stainless steel dust, forming Mn3O4, MnCr2O4 and Ni (Fe,Cr)O4 in the system, with a regular polyhedral structure. The prepared pigments have excellent thermal stability at 1100 °C and good compatibility with transparent glazes, which can be adhered to the surface of ceramic tiles after calcination to demonstrate better compatibility as the content of MnO increases.

Life Cycle Carbon Emissions and an Uncertainty Analysis of Recycled Asphalt Mixtures

The efficient recycling of road materials is an effective way to reduce carbon emissions. Approximately 400 million tons of waste asphalt pavement materials is generated annually in China, but the utilization rate is less than 50%. In this paper, a whole life cycle CO2 emission calculation model for recycled asphalt mixtures is established, and an uncertainty analysis is carried out on the basis of this model. The steps in the recycled asphalt mixture stage with the greatest impact on emissions are identified. The life cycle of asphalt mixtures is divided into raw material production, mixture preparation, material transportation and construction phases based on the carbon emission trends in the four phases. First, recycled asphalt mixtures are considered, and the carbon emissions along a two-way four-lane highway are analyzed based on the relevant carbon emission factor and other known data. The carbon dioxide emissions of each stage are also compared to identify the key links among stages. Then, the carbon emissions of hot-recycled asphalt mixtures are compared with those of ordinary asphalt mixtures and cold-recycled asphalt mixtures in each stage. Finally, an analytical uncertainty study of recycled asphalt mixtures is conducted using uncertainty modeling in different scenarios. Based on the quantitative results of the carbon emission calculations through life cycle assessment (LCA), future measures for reducing carbon emissions from recycled asphalt mixtures are proposed.

Development of lab-scale gasification systems for different possible applications

The goal of gasification is the conversion of solid fuels or carbonaceous wastes to gas that can be further used energetically or for chemically utilisation. Due to cost-effectiveness and gaining experience, the industrial application of new systems and raw materials or mixtures must be preceded by laboratory-scale experiments. The manuscript presents the laboratory scale gasification systems we designed and used, as well as the difficulties experienced during the implementation (e.g. water introduction, sealing, etc.). In addition to these, the results of one-, two- and three-stage experiments are presented as examples, where different materials such as a mixture of wood and canteen waste, brown coal and refuse derived fuel (RDF) were used for testing the system.

Effect of ethanol additive on bio-mix biodiesels from a raw mixture of various feedstocks

Effect of ethanol additive on bio-mix biodiesels from a raw mixture of various feedstocks

Effect of l-cysteine on functional properties and fibrous structure formation of 3D-printed meat analogs from plant-based proteins

The development of three-dimensional (3D) printed meat analogs with fiber, texture, and sensory resembling meat remains challenging. This study investigated the effect of l-cysteine on functionality enhancement and fibrous structure formation in mixtures of mung bean protein isolate (MBPI) and wheat gluten (WG) for meat analog production. 3D printing was used to construct fibrous filaments. Raw MBPI-WG mixtures decreased rheological properties when increasing l-cysteine contents (0.0%–0.6%), promoting ink extrudability. The cys-0.4% ink exhibited the highest printing resolution and structural stability, correlated with its higher mechanical strength and increased disulfide cross-links. After cooking, the cys-0.4% sample showed a pronounced fibrousness in agreement with its microstructure image. This meat analog displayed a muscle-meat-like structure, improved texture, and reduced beany odor and bitter taste. Excessive cysteine contents (0.5%–0.6%) negatively affected the functionality of meat analogs. This study provides guidance for optimizing the amount of l-cysteine in meat analogs to improve product quality.

A review of self-sensing ultra-high performance concrete: Towards next-generation smart structural materials

Today, the desired intelligent civil engineering structures urge the development of high-performance smart structural materials. Self-sensing ultra-high performance concrete (UHPC) emerged in 2014 based on the observation that the concrete structures rendered with randomly distributed conductive additives exhibit electromechanical effects under external loading, and the demand of UHPC from high-strength to sustainable, intelligent, and multifunctional. This smart structural material has since grown greatly and has been considered as one of the potential alternatives to ordinary self-sensing concrete. This paper presents a state-of-the-art review of self-sensing UHPC in terms of its raw materials, mixture design, manufacturing approaches, microstructural characteristics, mechanical properties, electrical resistivity, electromechanical properties, and applications, with a particular focus on stress-deformation/damage behaviour and changes in electrical conduction under external compression, tension, and bending. The novel uncertainties regarding electromechanical effects are thoroughly discussed from the perspective of the continuity of conductive network. Compared with ordinary self-sensing concrete, self-sensing UHPC exhibits significantly reduced porosity, exceptional strength, marginally lower stress/strain sensitivity, heightened damage sensitivity, insensitivity to humidity, and delayed cracking behaviour. In the end, this paper identifies research gaps, challenges, and recommendations in three aspects: (1) scale fabrication and cost control, (2) satisfactory and reliable properties, and (3) from smart structural materials to integrated components to civil engineering structures.

Նեֆելինային սիենիտներից կավահողաբելիտային ցեմենտի բաղադրության մշակում

The paper studies the nepheline syenites of the Hrazdan Tezh Mountain deposit as a raw material for the production of alumina-belite cement. Based on the research results, a two-component raw material mixture was calculated using limestone travertines from the Ararat deposit, with the addition of gypsum and a mineral-forming additive to the composition of the charge from limestone and syenite. Belite and low-basic calcium aluminates were identified as the main phases in the clinkers fired from these components.

Effect of microwave radiation temperature and content of different solid waste on the microstructure and physicomechanical properties of lightweight aggregates

Microwave radiation in the production of lightweight aggregates, it has not yet been thoroughly explored. Therefore, the main goal of the research is to analyze the possibility of using various types of waste, such as waste rock (0–30 %) and glass cullet (10 %), fly ash (50–80 %) and waste solution using different microwave temperature (1000, 1050, 1100 °C) in order to obtain lightweight aggregates. Above factors and, chemical and mineral composition of the waste materials, affect the microstructure and physico-mechanical parameters of the aggregates.). The thermophysical behavior (DTG/TG), grain composition, chemical composition (XRF), phase composition (XRD) and microstructure (SEM, μ-CT) were analyzed. The microstructure, as well as the related characteristics of aggregates, i.e. water absorption, density, and compressive strength, depend on the sintering temperature, chemical composition and mineral waste raw material. The best properties were obtained for a raw material mixture containing 80 % coal fly ash, 10 % glass cullet, 10 % clay and 48 g of the waste solution (per 100 g of raw mixture), sintered in the microwave at 1100 °C. The aggregates were characterized by water absorption of 6.96 %, bulk of 1.70 g/cm3, loose bulk density 0.60 g/cm3, and compressive strength 5.95 MPa. Closed porosity determined by micro-CT was 8.41 %, open - 0.24 %, sphericity 0.62. The total porosity depends on the loose bulk density and particle density of lightweight aggregates.Furthermore, washout tests meet environmental requirements. The proposed technology, moreover, enables a short time of thermal processing of raw materials, and thus energy savings and a sustainable approach to the production of green pellets. Thanks to the high strength, the obtained aggregates can replace commercial aggregates.