Recyclable Materials for Ecofriendly Technology.

This Special Issue (SI), "Recyclable Materials for Ecofriendly Technology", has been proposed and organized as a means to present recent developments in the field of environmentally friendly designed construction and building materials. For this purpose, dozens of articles were included or considered for inclusion in this SI, covering various aspects of the topic. A comparison of these articles with other modern articles on this topic is carried out, which proves the prospects and relevance of this SI. Furthermore, per the editorial board's journal suggestion, the second volume of this successful SI is being organized, in which authors from various countries and organizations are invited to publish their new and unpublished research work.

Hardening of Bimetallic Wires from Secondary Materials Used in the Construction of Power Lines.

Copper-sheathed steel wires combine the conductivity of copper and the traction resistance of steel, which makes a bimetallic wire an ideal material for the construction of power lines. Currently, there is a small number of studies devoted to the change in the microstructure of steel-copper wire during its strain. Since steel and copper have different mechanical properties, these metals at the interface can be deformed in different ways. Therefore, the present research is devoted to the study of ECAP-drawing process impacts on the properties of bimetallic steel-copper wire. During the conducted studies, the possibility and efficiency of using the combined strain technology for the formation of ultrafine grained structure and increased strength properties of steel-copper wire have been proved.

Development of a Thermomechanical Treatment Mode for Stainless-Steel Rings.

This article describes a technology for the thermomechanical treatment of stainless-steel piston rings. This technology makes it possible to obtain rings with an optimal combination of plastic and strength properties that is essential for piston rings. The following thermomechanical treatment is suggested for piston rings manufacturing: quenching at 1050 °C, holding for 30 min and cooling in water, then straining by the HPT method for eight cycles at cryogenic temperature and annealing at a temperature up to 600 °C. The resulting microstructure consisted of fine austenite grains sized 0.3 µm and evenly distributed carbide particles. Annealing above this temperature led to the formation of ferrite in the structure; however, preserving the maximum fraction of austenitic component is very important, since the reduction of austenite in the structure will cause a deterioration of corrosion resistance. The strength properties of steel after such treatment increased by almost two times compared with the initial ones: microhardness increased from 980 MPa to 2425 MPa, relative elongation increased by 20%. The proposed technology will improve the strength and performance characteristics of piston rings, as well as increase their service life, which will lead to significant savings in the cost of repair, replacement and downtime.

Porous Fly Ash/Aluminosilicate Microspheres-Based Composites Containing Lightweight Granules Using Liquid Glass as Binder.

The modern energy-saving vector of development in building materials science is being implemented in a complex way through the development of new heat-insulating materials with the simultaneous exclusion of low-ecological cement from them. This article presents the results of the development of resource-saving technology for a heat-insulating composite material. The research is devoted to the development of scientific ideas about the technology and properties of effective cementless lightweight concretes. The aim of the work is to create a heat-insulating composite material based on porous granules and a matrix from mixtures of liquid glass and thermal energy waste. The novelty of the work lies in establishing the patterns of formation of a stable structure of a porous material during thermal curing of liquid glass with technogenic fillers. Studies of liquid glass mixtures with different contents of fly ash and aluminosilicate microspheres revealed the possibility of controlling the properties of molding masses in a wide range. To obtain a granular material, liquid glass mixtures of plastic consistency with a predominance of aluminosilicate microspheres are proposed. The matrix of composite materials is formed by a mobile mixture of liquid glass and a combined filler, in which fly ash predominates. The parameters of heat treatment of granular and composite materials are established to ensure the formation of a strong porous waterproof structure. The possibility of regulating the structure of composite materials due to different degrees of filling the liquid glass matrix with porous granules is shown. A heat-insulating concrete based on porous aggregate has been developed, characterized by the genetic commonality of the matrix and the granular component, density of 380-650 kg/m3, thermal conductivity of 0.095-0.100 W/(m °C) and strength of 3.5-9.0 MPa, resistance under conditions of variable values of humidity and temperature. A basic technological scheme for the joint production of granular and composite materials from liquid glass mixtures is proposed.

Influence of Impurities on the Process of Obtaining Calcium Carbonate during the Processing of Phosphogypsum.

The article is devoted to the study of the influence of residual sulfuric and phosphoric acids on the process of processing large-tonnage phosphogypsum (PG) waste into calcium carbonate. In the Russian Federation, about 10 percent of existing phosphogypsum waste is processed into construction materials. Acidic impurities (phosphoric and sulfuric acids) in their composition are an obstacle to the use of phosphogypsum for the production of binders. This study finds that impurities also reduce the chemical activity of phosphogypsum. At the same time, the paper focuses on the potential of phosphogypsum for the production of calcium carbonate. This article investigated the amount of impurities in phosphogypsum. The results show that during automatic washing of phosphogypsum, losses are approximately 30-35 wt. %. It was also found that phosphogypsum by 22% consists of impurities of phosphoric and sulfuric acid. These acids are characteristic waste products of extraction phosphoric acid (EPA) production. By ASTM C471M-20ae1, the content of calcium sulfate dehydrate and hemihydrate before and after washing was determined. A thermodynamic calculation of the proposed interaction of phosphogypsum with carbonates showed that the characteristic reaction is possible. The conversion process of phosphogypsum to get the corresponding calcium carbonate was carried out at 70 °C. Data on the chemical composition of the reaction products, obtained by X-ray fluorescence analysis on a Shimadzu EDX-7000 spectrometer, showed that some reactions proceed incompletely and need the selection of optimal conditions. The potential commercial benefits of processing phosphogypsum by carbonization were defined for products such as calcium carbonate or its derivatives.

Drop Weight Impact Test on Prepacked Aggregate Fibrous Concrete-An Experimental Study.

In recent years, prepacked aggregate fibrous concrete (PAFC) is a new composite that has earned immense popularity and attracted researchers globally. The preparation procedure consists of two steps: the coarse aggregate is initially piled into a mold to create a natural skeleton and then filled with flowable grout. In this instance, the skeleton was completely filled with grout and bonded into an integrated body due to cement hydration, yielding a solid concrete material. In this research, experimental tests were performed to introduce five simple alterations to the ACI 544 drop weight impact test setup, intending to decrease result dispersion. The first alteration was replacing the steel ball with a steel bar to apply a line impact instead of a single point impact. The second and third introduced line and cross notched specimens at the specimen's top surface and the load applied through a steel plate of cross knife-like or line load types. These modifications distributed impact load over a broader area and decrease dispersion of results. The fourth and fifth were bedding with sand and coarse aggregate as an alternate to the solid base plate. One-hundred-and-eight cylindrical specimens were prepared and tested in 12 groups to evaluate the suggested alteration methods. Steel and polypropylene fibers were utilized with a dosage of 2.4% to produce PAFC. The findings indicated that the line notched specimens and sand bedding significantly decreased the coefficient of variation (COV) of the test results suggesting some alterations. Using a cross-line notched specimen and line of impact with coarse bedding also effectively reduced COV for all mixtures.

Improving the Durability of Lime Finishing Mortars by Modifying Them with Silicic Acid Sol.

Lime materials are in great demand for the restoration of the walls of historical buildings. However, lime coatings have insufficient resistance during operation. The purpose of this work was the modification of lime mortars with silicic acid sol in order to obtain more durable crystalline materials for construction purposes. A technology has been developed for obtaining a silica-containing additive, which consists in passing a liquid glass solution with a density of 1.053 kg/m3 through a cationic column and obtaining a silicic acid sol with a pH of 3-4 and a charge of (-) 0.053 V. The regeneration time and the amount of sol have been determined. Regularities of change in the radius of particles of silicic acid sol depending on age are determined. It is established that at an early age (up to 5 days), the radius of sol particles can be determined in accordance with the Rayleigh equation, and at a later age, in accordance with the Heller equation. The results of the calculation show that at the age of 1-5 days, the radius of the sol particles is 17.1-17.9 nm, and then the particles become coarser and the particle radius is 131.2-143 nm at the age of 19 days. The work of adhesion of silicic acid sol to lime and the heat of wetting are estimated. It is shown that the work of adhesion of water to lime is 28.9 erg/cm2, and that of the sol is 32.8 erg/cm2. The amount of heat Q released when lime is wetted with SiO2 sol is 15.0 kJ/kg, and when lime is wetted with water, it is 10.6 kJ/kg.

Reliability Analysis of Reinforced Concrete Structure with Shock Absorber Damper under Pseudo-Dynamic Loads.

Past historical earthquake events from neighbouring countries have been proven to be disastrous. Building in the aftermath of an earthquake may reduce structural reliability, posing risk upon re-occupation of the building. Shock absorber viscous dampers were installed on a specific structure storey that could reduce the spectral acceleration and storey-drift caused by an earthquake. The research object is a low-rise, three-storey, reinforced concrete (RC) structure. This study aims to identify the dynamic response of the scaled RC structure with and without attached dampers and performs structural reliability of the tested model under the excitation of Peak Ground Acceleration (PGA) of 0.1 g to 1.0 g with a unidirectional shaking table. APIDO viscous dampers were installed parallel to the movement direction of the dynamic load test. The findings show the scaled model with attached viscous dampers reduces spectral acceleration and storey drift by 9.66% and 4.85%, respectively. Findings also show the change of the structural behaviour from single curvature to double curvature due to the increase in seismic structural resistance by viscous dampers. The breakthrough of this research shows that structural reliability analysis performed by the Weibull distribution function has a base shear capacity increment of 1.29% and 6.90% in seismic performance level Life Safety (LS) and Collapse Prevention (CP), respectively. The novelty of this case study building with dampers managed to increase the building's base shear and roof shear capacity by 6.90% and 16% compared to the building without dampers under dynamic load excitation.

Structural Formation of Soil Concretes Based on Loam and Fly Ash, Modified with a Stabilizing Polymer Additive.

Finding new ways of recycling production waste to improve the characteristics of various building materials is an urgent scientific task. This article substantiates the possibility of the disposal of fly ash in the composition of soil concrete, which is used in the construction of the structural layers of road pavements, foundations of buildings and structures, as well as sites for various purposes. The scientific novelty lies in the fact that the structure formation of soil concretes based on loam and fly ash and modified with a stabilizing additive is being studied for the first time. It was found that the investigated fly ash, according to its hydraulic properties, is classified as latent active and can be introduced into the compositions of road soil concrete modified with additives of various resources. The effectiveness of the complex method of stabilization, due to changes in soil properties as a result of the use of the binding and stabilizing additives of polymer nature "Kriogelit", is shown. It was found that the optimal content of binder and fly ash in the samples was 8 and 10 wt.%, respectively. It was established that the use of the stabilizing additive "Kriogelit" makes it possible to obtain soil concrete with the highest strength (compressive strength 2.5 MPa, flexural strength 0.5 MPa) and frost resistance of at least F15. The microstructure, the degree of dehydration and carbonization, and the phase composition of the initial raw mixtures and soil concretes stabilized with the addition of "Kriogelit" were studied by methods of scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. It was shown that organo-mineral complexes, with the participation of polymer and montmorillonite, are formed in stabilized soil concrete. It was revealed that structure formation is accompanied by the physical adsorption of the polymer on active centers of silicate minerals, carbonization, and hydration-dehydration processes. It was found that the reason for the increase in the strength of stabilized soil concretes is the hydrophobization of the porous structure of minerals, as well as the formation of calcium oxide silicate and dicalcium hydrated silicate. By the method of performing biotests with the test objects Daphnia magna Straus and Chlorella vulgaris Beijer, it was proven that the developed road concretes modified with the stabilizing additive "Kriogelit" do not have an acute toxic effect on the test objects and are safe for the environment and human health.

The Effect of POFA-Gypsum Binary Mixture Replacement on the Performance of Mechanical and Microstructural Properties Enhancements of Clays.

Soft clay is categorized as problematic due to its weak and dispersive properties which requires stabilization. In Malaysia, there is another challenge, the increment of palm oil waste productions to meet the global demand for food oil. These two concerns motivate engineers to develop novel strategies for exploiting palm oil waste in soil stabilization. Utilizing POFA as a soil stabilizing agent is an economical and sustainable option due to that POFA contains high pozzolanic characteristics which make it more suitable and reliable to treat soft soil. This study uses the replacement portion of the soil with stabilizing agents -POFA and Gypsum; aiming to achieve Malaysia green technology goals by the balance of the economic expansion and environmental privilege. However, the aim of this study is to determine the effect of POFA-gypsum binary mixture replacement on the performance of mechanical and microstructural properties en-hancements of clays. Kaolin S300 is the control sample whereas POFA and gypsum are the used binders. The mechanical properties and shear strength with the curing period were tested. Results showed that treated clay marked increment of optimum water contents and reduction of maximum dry densities, a clear 200% of enhancement of treated clay's compressive and shear strength with curing period as well as the amount of stabilizing agent to less than 15% of POFA and 6% of POFA. It is also found that as gypsum contains a high amount of lime (CaO), the results illustrate that strength raises significantly even with less curing time due to its high reactivity compared to silica and alu-mina. Overall, the results show an enhancement of mechanical and shear strength properties of treated kaolin supported by microstructural SEM imaging.

Processing of Waste from Enrichment with the Production of Cement Clinker and the Extraction of Zinc.

This paper presents studies on the processing of enrichment tailings as a component of a raw mixture in order to obtain cement clinker, with simultaneous distillation of zinc. Thermodynamic studies were carried out in the temperature range of 600-1600 °C using the software application "HSC Chemistry 6" developed by the metallurgical company Outokumpu (Finland). As a result of the conducted studies, we found that zinc contributes to the intensification of mineral formation of cement clinker. In particular, it was found that the formation of belite is possible in the temperature range from 990.7 to 1500 °C with Gibbs energy values of -0.01 and -323.8 kJ (which is better than the standard process by -11.4 kJ), respectively; the formation of alite is possible in the temperature range from 982.9 to 1500 °C with Gibbs energy values of -0.05 and -402.1 kJ (better than the standard process by -11.4 kJ), respectively; the formation of tricalcium aluminate is thermodynamically possible in the temperature range from 600 °C at ΔGTo = -893.8 kJ to 1500 °C at ΔGTo = -1899.3 kJ (better than the standard process by -1570.1 kJ), respectively; and the formation of four calcium aluminoferrite is possible in the temperature range from 600 °C at ΔGTo = -898.9 kJ to 1500 °C at ΔGTo = -1959.3 kJ (better than the standard process by -1570.2 kJ), respectively, with simultaneous distillation of zinc into a gaseous state for its further capture.

Structural Formation of Alkali-Activated Materials Based on Thermally Treated Marl and Na2SiO3.

Modern materials science is aimed towards abandoning Portland cement in the production of building materials. The scientific novelty of this study lies in its being the first time a comprehensive study of the structure formation of alkali-activated materials (AAM) based on thermally treated marl and Na2SiO3 is carried out. The tasks for achieving this goal were to characterize the thermally treated marl as a new binder, and to comprehensively research the microstructure, fresh, physical, and mechanical properties of the AAM based on the binder. Received active particles of marl with a smaller size than Portland cement have a specific surface area of 580-590 m2/kg. The mineral composition of heat-treated marl is characterized by calcium silicates, which guarantee good binding properties. The results of X-ray diffraction analysis of the samples based on the clinker-free binder of alkaline activation using opoka-like marl confirmed the presence of calcite, quartz, and feldspar close to albite, micas, and zeolites. The obtained products of the chemical interaction of the components of the binder confirm the effectiveness of the newly developed AAM. As a result of comparing several binders, it was found that the binder "thermally treated marl-Na2SiO3" is the most effective, since for specimens based on it, a maximum compressive strength of 42.6 MPa, a flexural strength of 4.6 MPa, and minimum setting time were obtained (start 26 min, end 32 min) as well as a water absorption of 10.2 wt.%. The research results will be of interest to specialists in the construction industry, since the proposed recipes for clinker-free cements are an alternative to expensive and energy-intensive Portland cement and provide the creation of strong and durable concrete and reinforced concrete composites.

Coal Ash Enrichment with Its Full Use in Various Areas.

Increasing the percentage of recycling of various industrial waste is an important step towards caring for the environment. Coal ash is one of the most large-tonnage wastes, which is formed as a result of the operation of thermal power plants. The aim of this work is to develop a technology for the complex processing of coal ash. The tasks to achieve this aim are to develop a technology for the complex enrichment and separation of coal ash into components, with the possibility of their use in various applications, in particular: processing the aluminosilicate part as a pozzolanic additive to cement; carbon underburning for fuel briquettes; the iron-containing part for metallurgy and fertilizers. Complex enrichment and separation into components of coal ash were carried out according to the author's technology, which includes six stages: disintegration, flotation, two-stage magnetic separation, grinding, and drying. The aluminosilicate component has a fairly constant granulometric composition with a mode of 13.56 µm, a specific surface area of 1597.2 m2/kg, and a bulk density of 900 kg/m3. The compressive strength for seven and twenty-eight daily samples when Portland cement is replaced by 15% with an aluminosilicate additive, increases to 30-35%. According to the developed technology, high-calorie fuel briquettes are obtained from underburnt with a density of 1000-1200 kg/m3, a calorific value of 19.5-20 MJ/kg, and an ash content of 0.5-1.5%. The iron-containing component, recovered by two-stage magnetic separation, has the potential to be used in metallurgy as a coking additive, in particular for the production of iron and steel. In addition, an effective micro-fertilizer was obtained from the iron-containing component, which: is an excellent source of minerals; improves the quality of acidic soil; helps soil microorganisms decompose organic matter faster, turning it into elements available to plants; promotes rooting of seedlings; helps to more effectively deal with many pests and diseases. As a result, the complete utilization of coal ash in various applications has been achieved.

Recycling of Cement Industry Waste for Alkali-Activated Materials Production.

The cement industry is recognized as an environmental nuisance, and so there is a need to not only minimizes the consumption of cement, but also to completely recycle the waste of the cement industry. This paper's originality lies in the fact that, for the first time, a comprehensive study of the structure formation of alkali-activated materials (AAM) based on aspiration dust and clinker dust has been carried out. The tasks for achieving this goal were to characterize cement production waste as a new binder and comprehensively research the microstructure, fresh, physical, and mechanical properties of alkali-activated material based on a cement-free binder. Grains of cement production waste are represented by coarse volumetric particles with pronounced cleavage, and a clear presence of minerals is observed. The mineral composition of cement production waste is characterized by calcium silicates, which guarantee good binding properties. The results of the X-ray diffraction analysis of the samples (based on the alkaline-activated cement-free binder using clinker dust and aspiration dust) confirmed the presence of calcite, quartz, feldspar close to albite, micas, and zeolites. The obtained products of the chemical interaction of the binder components confirm the effectiveness of the newly developed AAM. As a result of comparing several binders, it was found that the binder based on aspiration dust with Na2SiO3 and Na2SiF6 was the most effective, since, for specimens based on it, a density of 1.8 g/cm3, maximum compressive strength of 50.7 MPa, flexural strength of 5.6 MPa, minimum setting time (starting at 24 min and ending at 36 min), and water absorption of 12.8 wt. % were obtained. The research results will be of interest to specialists in the construction industry since the proposed recipes for eco-friendly, alkali-activated materials are an alternative to expensive and energy-intensive Portland cement, and they provide for the creation of strong and durable concrete and reinforced concrete composites.

Mixed Finite Element Formulation for Navier-Stokes Equations for Magnetic Effects on Biomagnetic Fluid in a Rectangular Channel.

The article presents the mixed finite element formulation for examining the biomagnetic fluid dynamics as governed by the Navier-Stokes equation, coupled with energy and magnetic expressions. Both ferrohydrodynamics and magnetohydrodynamics describe the additional magnetic effects. For model discretization, the Galerkin weighted residual method was performed. Departing from a good agreement with existing findings, a biomagnetic flow (blood) in a straight rectangular conduit was then simulated in the presence of a spatially changing magnetic distribution. By virtue of negligible spatial variation influence from the magnetic field, the effects of Lorentz force were not presently considered. It was further found that the model accurately exhibits the formation and distribution of vortices, temperature, and skin friction located adjacent to and remotely from the source of magnetic load following a rise in the magnetic intensity.

Effects of Admixtures on Energy Consumption in the Process of Ready-Mixed Concrete Mixing.

The production and utilization of concrete and concrete-based products have drastically increased with the surge of construction activities over the last decade, especially in countries such as China and India. Consequently, this has resulted in a corresponding increase in the energy used for the production of ready-mixed concrete. One approach to reduce the cost of concrete manufacturing is to reduce the energy required for the manufacturing process. The main hypothesis of this study is that the power required for mixing the concrete can be reduced through the use of mineral admixtures in the mix design. Optimization of energy consumption during mixing using admixtures in concrete manufacturing is the predominant focus of this article. To achieve this objective, power consumption data were measured and analyzed throughout the concrete mixing process. The power consumption curve is the only source to distinguish the behavior of the different materials used in the concrete in a closed chamber. In the current research, fly ash and ground granulated blast-furnace slag (GGBS) were used as mineral admixtures to produce ready-mixed concrete. The experimental study focused on the influence of GGBS and fly ash on power consumption during concrete mixing. The results indicated that the use of a higher content of GGBS is more beneficial in comparison to the use of fly ash in the mix due to the lower mixing time required to achieve homogeneity in the mixing process. It was found that the amount of energy required for mixing is directly related to the mixing time for the mix to achieve homogeneity.

Effect of Steel Fiber on the Strength and Flexural Characteristics of Coconut Shell Concrete Partially Blended with Fly Ash.

The construction industry relies heavily on concrete as a building material. The coarse aggregate makes up a substantial portion of the volume of concrete. However, the continued exploitation of granite rock for coarse aggregate results in an increase in the future generations' demand for natural resources. In this investigation, coconut shell was used in the place of conventional aggregate to produce coconut shell lightweight concrete. Class F fly ash was used as a partial substitute for cement to reduce the high cement content of lightweight concrete. The impact of steel fiber addition on the compressive strength and flexural features of sustainable concrete was investigated. A 10% weight replacement of class F fly ash was used in the place of cement. Steel fiber was added at 0.25, 0.5, 0.75, and 1.0% of the concrete volume. The results revealed that the addition of steel fibers enhanced the compressive strength by up to 39%. The addition of steel fiber to reinforced coconut shell concrete beams increased the ultimate moment capacity by 5-14%. Flexural toughness was increased by up to 45%. The span/deflection ratio of all fiber-reinforced coconut shell concrete beams met the IS456 and BS 8110 requirements. Branson's and the finite element models developed in this study agreed well with the experimental results. As a result, coconut shell concrete with steel fiber could be considered as a viable and environmentally-friendly construction material.

Cyclically Loaded Copper Slag Admixed Reinforced Concrete Beams with Cement Partially Replaced with Fly Ash.

Generally, the concrete with higher strength appears to produce brittle failure more easily. However, the use of mineral admixture can help in enhancing the ductility, energy dissipation, and seismic energy in the designed concrete. This paper presents energy absorption capacity, stiffness degradation, and ductility of the copper slag (CS) admixed reinforced concrete with fly ash (FA) beams subjected to forward cyclic load. The forward cyclic load was applied with the help of servo-hydraulic universal testing machines with 250 kN capacity. Twenty-four beams with a size of 100 mm × 150 mm × 1700 mm made with CS replaced for natural sand from 0% to 100% at an increment of 20%, and FA was replaced for cement from 0% to 30% with an increment of 10% were cast. Beams are designed for the grade of M30 concrete. Based on the preliminary investigation results, compressive strength of the concrete greatly increased when adding these two materials in the concrete. Normally, Grade of concrete can change the behaviour of the beam from a brittle manner to be more ductile manner. So, in this work, flexural behaviour of RC beams are studied with varying compressive strength of concrete. Experimental results showed that the RC beam made with 20% FA and 80% CS (FA20CS80) possesses higher ultimate load-carrying capacity than the control concrete beam. It withstands up to 18 cycles of loading with an ultimate deflection of 60 mm. The CS and FA admixed reinforced concrete composite beams have excellent ultimate load carrying capacity, stiffness, energy absorption capacity, and ductility indices compared to the control concrete beam.

Self-Healing Concrete as a Prospective Construction Material: A Review.

Concrete is a material that is widely used in the construction market due to its availability and cost, although it is prone to fracture formation. Therefore, there has been a surge in interest in self-healing materials, particularly self-healing capabilities in green and sustainable concrete materials, with a focus on different techniques offered by dozens of researchers worldwide in the last two decades. However, it is difficult to choose the most effective approach because each research institute employs its own test techniques to assess healing efficiency. Self-healing concrete (SHC) has the capacity to heal and lowers the requirement to locate and repair internal damage (e.g., cracks) without the need for external intervention. This limits reinforcement corrosion and concrete deterioration, as well as lowering costs and increasing durability. Given the merits of SHCs, this article presents a thorough review on the subject, considering the strategies, influential factors, mechanisms, and efficiency of self-healing. This literature review also provides critical synopses on the properties, performance, and evaluation of the self-healing efficiency of SHC composites. In addition, we review trends of development in research toward a broad understanding of the potential application of SHC as a superior concrete candidate and a turning point for developing sustainable and durable concrete composites for modern construction today. Further, it can be imagined that SHC will enable builders to construct buildings without fear of damage or extensive maintenance. Based on this comprehensive review, it is evident that SHC is a truly interdisciplinary hotspot research topic integrating chemistry, microbiology, civil engineering, material science, etc. Furthermore, limitations and future prospects of SHC, as well as the hotspot research topics for future investigations, are also successfully highlighted.

Modeling of Non-Ferrous Metallurgy Waste Disposal with the Production of Iron Silicides and Zinc Distillation.

This paper presents studies on the possibility of utilization of technogenic waste from the metallurgical industry by the method of complex processing in order to reduce the anthropogenic load on the environment of the region with the example of the zinc silicate-magnetite-carbon system. The selected sample of clinker dump from welting was subjected to chemical and scanning electron microscopic analyses and thermodynamic modeling. Thermodynamic studies were carried out in the temperature range 1600-2200 K and pressure p = 0.1 MPa, modeling the process of electric melting of clinker from welting in an arc furnace using the software application Astra 4 developed at the Bauman Moscow State Technical University (Moscow, Russian Federation). As a result of the thermodynamic modeling, the optimal temperature range was established, which was 1800-1900 K. Thermodynamic studies established that it is possible to drive away zinc from the system under study by 99-100% in the entire temperature range under study. The maximum degree of silicon extraction (αSi) in the alloy is up to 69.44% at T = 1900 K, and the degree of iron extraction (αFe) in the alloy is up to 99.996%. In particular, it was determined and proved that clinker waste from welting can act as a secondary technogenic raw material when it is processed as a mono mixture to produce iron silicides with a silicon content of 18 to 28%.