Polyanskikh, Irina S

Gordina A.F., Gumenyuk A.N., Polyanskikh I.S., Gafipov A.T.

Gordina A., Gumenyuk A., Polyanskikh I., Yakovlev G., Pudov I.

Destructive processes accompanying sulfate corrosion of concrete significantly affect the durability of products and structures based on Portland cement. In the presented study, the long-term effect of sulfate corrosion on the electrical properties of electrically conductive sand concrete was studied. In the course of the study, the following were tested: an electrically conductive composition and a control composition based on plain Portland cement. The analysis of changes in the mineral composition of the samples over the course of time in an aggressive solution was carried out. The results show that during the exposure period of the samples from 28 to 224 days, the absorption of sulfate ions slows down and averages 26% for the control composition and 29% for the electrically conductive composition, of the total volume of absorbed sulfates. At the same time, the course of sulfate corrosion was accompanied by a 6% increase in the density of samples of both compositions, as well as a cyclic change in mechanical strength within 15%. In its turn, the key indicator of the electrical characteristics of the compositions—electrical resistivity—tended to increase throughout the experiment. These results can be recommended for assessing the durability and the nature of the operating conditions of electrical concretes used in aggressive environments.

Gordina A.F., Gumenyuk A.N., Polyanskikh I.S., Zaripova R.I.

Saidova Z., Yakovlev G.I., Polyanskikh I.S., Begunova E.V., Buryanov А.F.

This article presents the results of a study on the effect of carbon nanosized additives on the structure and properties of cement-based materials. The use of a carbon black dispersion as an alternative to an expensive dispersion of carbon nanotubes is proposed. Based on the experimental data, it is proven that the introduction of carbon black particles into the composition of the cement matrix in an amount of 0.2% by the weight of cement leads to an increase in strength of the cement stone, in both compression and bending, by 21% and 8%, respectively. This increase is compatible with the results obtained when cement matrix was modified with a dispersion of carbon nanotubes.IR spectral and thermal analysis of the modified cement matrix, as well as the study of its microstructure, confirm the formation of a dense net of cement hydration products, including low-basic calcium silicate hydrates and secondary nanosized globular thaumasite formations that contribute to the compaction of the material structure and the following increase in strength.

Aleksandr Gumeniuk, Irina Polyanskikh, Anastasiya Gordina, Grigorij Yakovlev, Igor Averkiev, Filipp Shevchenko

The article represents the results of using industrial sulfur as an additive to a fluoroanhydrite based binder and the estimation of its influence on mechanical and physicochemical properties. Waste generated by human activities on an industrial scale, such as industrial sulfur and fluoroanhydrite, pose a serious environmental problem in terms of storage and disposal. Moreover, industrial sulfur and fluoroanhydrite have particular properties to form composite material with required properties. A number of studies have been carried out on using industrial waste as components of building materials, performance properties of the products obtained being improved and the functional use of the products being expanded. In order to study changes in the mechanical properties and physicochemical composition of material based on synthetic fluoroanhydrite, conventional testing methods accompanied by modern methods including scanning electron microscopy and X-ray analysis and infrared spectroscopy, were used. According to the obtained results compressive strength of composition modified with 10 % of thermoplastic additives was 35.77 MPa, water resistance was 0.68. This increase in mechanical properties is due to an interaction between chemically reactive polymorphic types of sulfur which are formed by transformation of α- type to β- and fluoroanhydrite binder. The results of the presented study prove the possibility of creating a building material, the composition of which is fully represented by industrial waste and the characteristics of which are not inferior to its analogues in terms of technical and economic properties.

YAKOVLEV G.I., CHERNY V., PUDOV I.A., POLYANSKIKH I.S., SAIDOVA Z.S., BEGUNOVA E.V., SEMYONOVA S.N.

GORDINA A.F., POLYANSKIKH I.S., GAFIPOV A.T., KUZMINA N.V., PUDOV I.A.

Gumenyuk A.N., Polyanskikh I.S., Pudov I.A., Shevchenko P.E., Kuzmina N.V., Yakovlev G.I.

Research results of modified composites which consist of isolated layers with different properties and their practical usages are represented in this article. A structure of the composite material is considered. The structure is combined of few layers; external layers are made of corrosive resistance material with dielectric behavior while the internal part of the composite is made of electrically conductive material with high conductive and mechanical properties. Conductive properties of each layer have been measured as well as their mechanical properties and structure. Also, the features of the joints between layers in terms of structure and properties were defined. More than that, varieties of mixtures and their possible usage are considered. Conductive properties of composite materials and ways of their adjustment have been described as well. For the first time, the measuring scheme of conductive properties for each layer was offered and heat shrinkable tubes and copper electrodes were used for it. Efficiency of modified composites and its behavior when electrical current applied can be measured by using the scheme.

Yakovlev G.I., Gordina A., Ruzina N., Polyanskikh I.S., Pudov I.A., Shaybadullina A., Khozin V., Černý V.

The main results of the study of the influence of man-made products of the metallurgical industry on the properties and structure of gypsum binder are presented. It has been proved that the introduction of man-made modifiers, metallurgical dust, and slag leads to an increase in the strength properties and electric conductivity of the material, but, over time, the waste efficiency decreases. The use of Portland cement as an activator leads to the formation of amorphous hydration products based on calcium hydrosilicates, which bind calcium sulfate crystals and provide an increase in the physicomechanical characteristics and electric behavior of the gypsum composite.

Yakovlev G.I., Drochytka R., Grakhov V., Saidova Z.S., Polyanskikh I.S., Pudov I.A.

The article describes the influence of chrysotile nanofibers dispersion introduction on the properties of the cement matrix. Comparison of the dispersion level of suspensions obtained using cavitation and ultrasonic processing methods is presented. The positive effect of chrysotile fibers application on the strength characteristics of the material has been confirmed. A 34% increase in the compressive strength of the samples was achieved on the 7th day of hardening, while on the 28th day it increased by 36% and with the steam treatment - by 38% compared to the reference sample. Laser particle size analysis confirmed the predominance of the nanosized component of chrysotile fibers in the suspension, which affected the structuring of the cement matrix. The results of the differential thermography, IR spectrometry, X-ray microanalysis and scanning electron microscopy of the samples are also presented. The analysis methods confirmed that introduction of chrysotile nanofibers suspension into the composition of a cement binder makes it possible to significantly vary the structure and morphology of new formations in fine-grained concrete. It also changes the quantitative and qualitative phase composition of the material with the formation of calcium silicate hydrates of lower basicity, leading to an increase in the strength of cement concrete.

Yakovlev G., Polyanskikh I., Gordina A., Pudov I., Černý V., Gumenyuk A., Smirnova O.

Monitoring the condition of building structures based on composite materials in aggressive environments shows that the deterioration of basic properties occurs under the influence of various factors such as temperature and humidity changes, in addition to changes in the chemical composition of air environment. In addition, the composite materials during the operation must retain not only the mechanical properties laid down at the design stage, but also the electro-physical characteristics, regardless of the type of destructive effects. In the current study, the quantitative assessment of the result of the interaction of an aggressive sulphate-containing medium with composites modified with conductive and dielectric additives was carried out. The effect of sulphate attack on the specific electrical conductivity of cement composites was studied. The nature of the interaction was evaluated by changing the properties of the samples of the developed compositions under the influence of a single-normal solution of sodium sulphate. The analysis was carried out by means of potentiometric titration using the exchange interaction method by fixing the degree of absorption of sulphate ions and determining the concentration of calcium ions in the solution. The measurement of the solution potential allowed determination of the quantitative indicators of the rate of calcium hydroxide leaching from the sample structure, which is necessary to assess the intensity of the destruction process and determine the nature of the change in strength properties. Measurements of the electrical resistivity of samples under the constant influence of sulphate aggression were taken during 28 days of observation. A method for quantifying the effect of a sulphate medium on a cement matrix was proposed that enables the material durability to be predicted. The features of changes in the morphology of structural components after exposure to aggressive solution were determined by physical and chemical methods.

Yakovlev G., Drochytka R., Skripkiūnas G., Urkhanova L., Polyanskikh I., Pudov I., Karpova E., Saidova Z., Elrefai A.E.

The present research is focused on the investigation of the influence of ultrafine additives on the structure formation of hardened cement paste and the establishment of the mechanisms of the morphological transformations, which determine the properties of hydrated products. In the course of the research, the modification of ordinary Portland cement was performed by the suspension of multi-walled carbon nanotubes (MWCNTs), carbon black (CB) paste, and silica fume (SF). Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD) analysis, thermal analysis, and Fourier-transform infrared (FTIR) spectroscopy were used to study cement hydration products. The morphology of hardened cement paste depends on the chemical reactivity of additives, their geometry, and their genesis. The action mechanism of the inert carbon-based additives and pozzolanic silica fume were considered. The cement hydration products formed in the process of modification by both types of ultrafine additives are described. In the case of the modification of cement paste by inert MWCNTs and CB paste, the formation of cement hydration products on their surface without strong adhesion was observed, whereas in the case of the addition of SF separately and together with MWCNTs, the strong adhesion of additives and cement hydration products was noted.

Gumeniuk A.N., Polyanskikh I.S., Petrunin S.M., Shevchenko F.E., Pervushin G.N.

Introduction. The adjustability of electrical properties of materials, that have hydraulic setting characteristics, has been studied over the last decades. It is emphasized that any change in electrical properties, triggered by various additives, causes negative side effects, including low corrosive resistance and modified physical and mechanical characteristics. The purpose of this research is to design a multifunctional layered material that features localized electrical conductivity. The objective is to track the influence of modifiers, capable of regulating electrical properties. Materials and methods. Samples were made of Portland cement I 42.5; the cement, having the fineness modulus of 0.7, was used as the aggregate; samples also contained ground Sulphur type 9998 (GOST 127.1-93), soot slurry, and calcium nitrate. The co-authors have identified the unit resistance values of each layer of this composite material, mechanical properties and features of each layer, and the structure of contact layers. Results. The co-authors have determined that the addition of pre-treated Sulphur in the amount of 7 % of the binder mass facilitates the formation of a nonconductive layer, whose unit resistance reaches 29.57 kiloohm cm on the 28th day. The conductive layer, generated by adding soot in the amount of 7 % of the binder mass, ensures the stable passage of electric current. The co-authors have identified that calcium nitrate influences the morphology of secondary crystalline hydrates and the non-crystalline phase of the mineral matrix, made of Portland cement, and it also ensures the required concrete strength. Conclusions. The layered method of formation of new compositions allows to make composite materials having adjustable electrical characteristics. New materials are made of Portland cement, and they contain no non-conductors. The co-authors have proven the efficiency of Sulphur, an integrated modifier made of soot and calcium nitrite, used as the modifiers of the mineral matrix, since they regulate the electrical properties of the artificial stone.

Yakovlev G., Polyanskikh I., Belykh V., Stepanov V., Smirnova O.

The need for research using modern methods of physical and chemical analysis in combination with methods for processing the graphical results arises with an increase of developments aimed at changing the structure and properties of hydration-hardening materials. Currently, the method of scanning electron microscopy is widely used for the qualitative and quantitative analysis of materials. Additional information, including fractal analysis of the image, determines the information-entropy levels and the state of the information system in the form of the microstructure based on the generalized structural entropy that increases the volume and quality of analytical information extracted from the obtained images. Images with a magnification of 20,000 times were used to analyze the microstructure of a control cement composite and a carbon black modified composite. The fractal analysis of the images revealed a change in the relative organization of the system, which justifiedthe nature of the change in the physical and technical properties of the modified cement composite relative to the additive-free cement composite from the perspective of self-organization.

Yakovlev G., Vít Č., Polyanskikh I., Gordina A., Pudov I., Gumenyuk A., Smirnova O.

The research results presented in this article were obtained by joint scientific research on creatingcement materials with reduced impedance. It is known that functional additives added to impart electrically conductive properties have a negative impact on physical and mechanical characteristics of the material. This study suggests using the multiwall carbon nanotubes in the amount of 7% from binder mass as a functional additive. The results obtained prove that the addition of this amount of the modifier does not lead to a significant decrease of strength characteristics. Calcium nitrate in the amount of 1–7% was added in order to level the strength loss and to ensure the effective stable electrical conductivity. The multifunctionality of using this salt has been proven, which is manifested in the anti-frost and anticorrosive effects as well in enhancement of electrical conductivity. The optimal composition of the additive with 7% of carbon nanotubes and 3% of calcium nitrate ensures a reduced electrical impedance of cement matrix. The electrical conductivity was 2440 Ohm, while the decrease of strength properties was within 10% in comparison tothe control sample. The nature of changes in the microstructure were studied to determine the influence of complex modifications that showed significant changes in the morphology of the hydration products. The optimum electrical characteristics of cementitious materials are provided due to the uniform distribution of carbon nanotubes and the formation of a network of interconnected micropores filled with the solution of calcium nitrate that provides additional and stable electrical conductivity over time.

Anjum N., Iqbal R.M., Zhang X., Karua P., Muntasir M., Islam M.S., Moinuddin K., Arifuzzaman M.

Jing Y., Lee J.C., Moon W.C., Ng J.L., Yew M.K., Jin Y.

The environmental issues in the construction industry have garnered considerable attention in numerous studies. Ecologically sustainable green concrete addresses environmental challenges in the construction industry. This study investigates the impact of multi-walled carbon nanotubes (0–0.20%) in rice husk ash (15%) concrete to replace Portland cement. The mechanical and durability properties of four concrete mixtures were analysed. Adding 0.1% multi-walled carbon nanotubes and 15% rice husk ash yielded satisfactory results, significantly improving durability compared to concrete without multi-walled carbon nanotubes. With the addition of 0.1–0.2% multi-walled carbon nanotubes, the density and elastic modulus increased, the 28-d sorptivity decreased by 4.64–28.76%. The resistance ability of 111-d mass loss and compressive strength loss increased by 50.93–61.71% and 25.28–48.47% under sulphate attack, respectively. The resistance ability of mass loss increased by 3.7–35.97% under acid attack. And 120-d drying shrinkage resistance improved by 3.08–9.23%. The predicted and experimental results were compared using the Sakata, GL 2000, B3, ACI 209, and CEB-FIP models. Sakata and B3 provided the most accurate early-stage and long-term drying shrinkages with variation coefficients of 0.13–0.33 and 0–0.05, respectively. Moreover, the sustainability of rice husk ash concrete containing multi-walled carbon nanotubes was evaluated, and its environmental friendliness was confirmed. Thus, the viability of multi-walled carbon nanotubes in rice husk ash sustainable concrete significantly contributes to sustainable construction.

Aaron G.H., Mydin M.A., Tobbala D.E., Jagadesh P., Özkılıç Y.O., Datta S.D., Al Bakri Abdullah M.M.

Sustainable dolomitic limestone (DL) and surkhi (SK) powders replace cement in lightweight foam concrete (LFC) for the first time. A total of fifteen LFC mixes were produced, which included reference mixtures. DL was used as a partial substitute for cement, with varying proportions ranging from 0 to 20% by weight. SK was employed as a partial replacement for cement, with weight fractions of 0, 15, and 30%. DL and SK were analyzed to determine how their integration affected slump flow, j-ring, oven-dry density, setting times, compressive strength (fc) and flexural strength (ff), modulus of elasticity (ME), ultrasonic pulse velocity (ν), water absorption (WA), apparent porosity (AP), air permeability (ko), microstructure, and pore distributions. In this investigation, Artificial Neural Network (ANN) is used to predict the compressive strength of LFC with help of K-fold cross validation. The assessment techniques are coefficient of correlation (R), coefficient of determination (R2), root mean square error (RMSE) and mean square error (MSE) metrics on training and testing datasets. All the LFC’s aspects were considerably improved by adding 10% DL and 15% SK. While replacing cement with them reduced the LFC’s density, it enhanced its workability, mechanical characteristics, and pore properties. Adding 10% DL and 15% SK at 28 days improved fc, ff, ME, ν, AP, WA, and ko. fc, ff, ME, and ko increased 2.5, 19, 6, and 4.3%, respectively. When LFC incorporated with 10% DL and 15% SK at 28 days, AP dropped 8.5%, WA reduced 8.6%, and ko rose 20%. The regression analysis utilizing the ANN method for K = 4 yielded the prediction accuracy (R2 = 0.94) of fc. The scanning electron microscopy revealed that the inclusion of a small quantity of DL and SK improved the microstructure of cement paste and accelerated the process of hydration. Overall, replacing 25% cement with DL and SK enhanced all evaluated qualities and reduced carbonation pollution, which will be contributing to the sustainability in the construction.

Rathour T.S., Khan F., Kodopi K., Sahu S., Sonkale S.

Concrete, a ubiquitous construction material globally, relies on natural resources such as lime, aggregates, and water. The surge in cement production has led to a significant rise in CO2 emissions, contributing to environmental pollution. In underdeveloped countries like India, enormous amounts of dolomite waste are generated annually. Owing to the large amount of area needed for disposal and the low amount of waste that is recovered or reused, dolomite waste disposal is a very serious issue. To mitigate these effects, researchers have explored alternative materials like Dolomite Powder to replace or supplement cement. This study delves into the potential of Dolomite Powder as a substitute for cement in concrete, presenting a cost-effective and strength-enhancing solution. Various replacement percentages (0, 5, 10, and 15% by weight of cement) were examined. The research evaluated compressive strength, flexural strength, split tensile strength, and workability revealing that incorporating dolomite powder improves these mechanical properties in concrete, suggesting a promising avenue for further exploration and application in the construction industry.

Zalpour N., Samsami R., Roushani M.

Carbon-based nanomaterials (CBNs), which encompass carbon nanotubes, porous carbons, carbon dots, graphenes, nanodiamonds, and fullerenes, possess distinct physical and chemical attributes that make them highly suitable for drug delivery purposes. These materials exhibit numerous advantages, including exceptional biocompatibility, a large surface area, and the ability to modify their surface chemistry as desired. The aforementioned attributes facilitate effective drug encapsulation, regulated release, and precise administration, rendering them highly suitable for drug delivery purposes. CBNs exhibit versatile properties and notable characteristics, including substantial drug-loading capability, improved stability, regulated release, and targeted delivery, thereby rendering them exceedingly appealing for drug carrier systems. Despite the considerable potential and promising characteristics of CBNs as drug carriers, there are several obstacles that must be addressed before their successful implementation in clinical settings. The issues encompass worries regarding their toxicity, acquiring regulatory endorsement, accomplishing mass production, and ensuring effective drug loading onto the nanomaterials. Overcoming these challenges will facilitate the advancement of innovative and efficient drug carrier systems, thereby revolutionizing the domain of healthcare. This chapter encompasses a comprehensive examination of several forms of CBNs, along with an exploration of the fundamental principles underlying their synthesis and their uses within the realm of drug carrier systems. This study showcases notable instances of remarkable materials and examines their diverse capabilities and potential applications as multifunctional drug carriers. Additionally, the problems associated with their utilization and the future prospects for their use are explored.

Zhenzhen Z., Yanfei G., Liting W., Binbin D., Tiekun J.

AbstractBeta‐hemihydrate desulfurization gypsum (β‐HDG) is considered one of the green and low‐carbon building materials, which is widely used in the fields of construction materials and decoration. Nevertheless, its inherent deficiency in water resistance and other drawbacks significantly limit its application scope. In this study, the gypsum‐based materials with surfaces that exhibit hydrophobic properties were prepared. The surface contact angle was analyzed to examine the surface hydrophobic characteristics. The compressive strength, flexural strength, ratio of compressive strength to flexural strength, water absorption rate, and softening coefficient of hardened specimens were measured to assess the mechanical properties. Furthermore, the pore structure and microstructure of hardened specimens were characterized to evaluate the impact of hydrophobically modified reduced graphene oxide (H@rGO). Furthermore, when the content of H@rGO was 0.15 wt%, the thermal conductivity of specimen was 0.55 W/m•K with optimal mechanical properties; the surface hydrophobicity of the hardened sample was significantly improved, with the surface contact angle, water drop penetration time, and softening coefficient reaching 113.898°, 567s, and 0.77, respectively. This enhancement was accompanied by a reduction in pore size and total porosity in the hardened samples, thereby contributing to the improved softening coefficient and mechanical properties of gypsum‐based composites. Because of lower energy consumption in H@rGO process and extensive utilization of industrial solid waste, the preparation process of incorporating H@rGO into β‐HDG exhibits superior cost‐effectiveness.

Liu Q., Lin W., Xi L.

AbstractThe dolomite dust-emulsified asphalt composite (DAC) with excellent mechanical properties was successfully prepared using alkali activation. The effects of different alkali concentrations and emulsified asphalt contents on the mechanical properties of the materials were studied. And the micro-mechanisms of its mechanical performance changes were analyzed through SEM and XRD characterization. The experimental results show that the specimens have excellent mechanical properties: the 7-day compressive strength can reach 76.67 MPa, and the bending and compressive strength ratio is about twice that of silicate-based geopolymer-emulsified asphalt composite (SAC). With an increase in emulsified asphalt content, the compressive strength of the samples decreases, while the bending strength increases first and then decreases. When the emulsified asphalt content is 1%, the bending strength of the sample is up to 28.81 MPa, which is 25% higher than that of the sample without emulsified asphalt. The in-situ formation of calcium carbonate crystal clusters within the DAC was suggested that may support this performance. This crystalline structuring contributes to an expanded interfacial contact area between the asphalt and skeleton particles, thereby enhancing the demulsification and bonding properties of the emulsified asphalt. This indicates that an appropriate emulsified asphalt content can play a toughening role in the system, providing a new idea for designing high-toughness alkali-activated materials.

Gumeniuk A., Gordina A., Petrynin S., Buryanov A.

The study focuses on the effect of electric current on the structure and properties of the fluorine-anhydrite sulfate-containing matrix modified with carbon fiber as well as assesses the possibility of using carbon fiber as microheating elements. The effect of the modifier on the performance characteristics and physicochemical properties of the mineral matrix was assessed using both traditional methods for determining electrical and thermal characteristics and modern ones, including scanning electron microscopy and differential thermal analysis. The results obtained confirm that the introduction of carbon fiber reduces the specific volume resistance of the product and provides uniform heating, which in turn allows the use of the proposed compositions for heating elements. Due to the achieved thermophysical characteristics, the products can be used as heating elements, provided that the pre-installed electrodes are protected from electrochemical corrosion found during the study using methods of physicochemical analysis.

Vilela L.S., Borges I.O., Arantes L.D., Satiro J.S., Miranda L.N., Lourenço Y.B., Guimarães Junior M., Mendes L.M., Guimarães Júnior J.B.

Abstract The present study aimed to replace plaster concentrations with cellulose micro/nanofibrils (CMF/CNF), evaluating the physical and mechanical properties of the nanocomposites. To make the nanocomposites, the plaster mass was replaced by levels of 0.5; 1; 1.5, and 2% (m/m) CMF/CNF. The nanocomposites were produced in dimensions of 40 x 40 x 160 mm. They were evaluated at 28 days through apparent density, water absorption, bending strength, compression strength, and microstructural analysis of the surface of the nanocomposites. The research results indicated an increase in apparent density and a decrease in water absorption for the nanocomposite with 0.5% CMF/CNF. The mechanical properties showed equivalent values for bending strength and increased compressive strength of the nanocomposites with 0.5% CMF/CNF compared to the control. The results found present an alternative trait to produce plaster, aiming to value CMF/CNF and to promote the sustainability of the civil construction sector.

Wang Q., Delplancke M., Snoeck D.

Sulfur mortar hardens quickly, shows a high chemical resistance, and can be recycled, making it ideal for construction and rehabilitation in extreme environments. Despite its potential for sustainability, current research lacks sufficient characterization of sulfur mortar’s performance during recycling, particularly regarding the physical and chemical changes when iron oxide is introduced. This study investigates the replacement of conventional siliceous sand with high-iron-content sand in sulfur mortar, through a series of five break–recast cycles. The results demonstrate an 11% increase in compressive strength and a 26% increase in flexural strength after five recasting cycles. Optical microscopy and scanning electron microscopy (SEM) revealed that recasting improved the distribution of the sulfur binder, while the formation of iron sulfates filled the gaps between aggregates and the binder. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) confirmed the presence of iron sulfates, and differential scanning calorimetry (DSC) showed that high-iron-content sulfur mortar narrowed the phase change temperature range, preventing uneven solidification within the samples. This study sheds light on the strengthening mechanisms that occur during the recycling process, enhancing the material’s durability and recyclability. This aligns with circular economy principles, contributes to resource efficiency, and supports sustainable construction practices.

Van Truong T., Perumal P., Kokko M., Pesonen J., Lassi U., Illikainen M.

Huang M., Bao S., Zhang Y., Zhou Z., Jiao X.

Liu F., Cao W., Yang T., Xu J., Lu D., Hooton R.D.

Kayutina S.V., Tonshin A.A., Karpukhina E.A., Krikunov O.V., Makarov A.F., Muravskaya M.P., Tkachuk Y.V., Blintsova N.V., Shishkov A.Y.

Introduction. The article tells about the widespread use of calcium nitrate (calcium nitrate, anhydrous calcium nitrate, calcium salt of nitric acid), about the use in the production of additives to concrete, deicing reagents, detergents, fertilizers and in other fields of human activity. There are data in the literature on the toxicity and danger of compounds similar in chemical structure, there is an approved maximum permissible concentration of calcium dinitrate in the atmospheric air of urban and rural settlements equal to 0.03 mg/m3 — the maximum single and 0.01 mg/m3 — the average daily in accordance with SanPiN 1.2.3685-21. However, the hygienic standard of calcium dinitrate in the air of the working area, which is necessary to ensure the preservation of the health of workers, has not yet been established. The study aims are the hygienic rationing of calcium dinitrate in the air of the working area based on the study of the toxic properties and nature of the biological action of the substance in various ways of entry into the body of experimental animals. Materials and methods. The authors had carried out experimental studies on non-harmless white rats of both sexes of the Wistar line, non-harmless white mice, white Agouti guinea pigs, rabbits of the Soviet Chinchilla breed in single and repeated experiments with oral, inhalation and percutaneous exposure. Experts have assessed the condition of experimental rats after a single inhalation exposure to calcium dinitrate at concentrations of 102.1±6.2 mg/m3 and 35.3±5.1 mg/m3 by changing physiological, hematological and biochemical parameters, taking into account literature data on compounds similar in chemical structure. Results. The DL50 value when the substance was injected into the stomach of male rats was 1633 (1407–18 894) mg/kg, for females — 1908±360 mg/kg, for mice — 1000±363 mg/kg (a moderately dangerous substance according to GOST 12.1.007-76). It has a weak accumulation, Kkum>8. Calcium dinitrate has a pronounced irritating effect on the skin of rabbits and guinea pigs, as well as on the mucous membrane of the eye of rabbits, does not penetrate through intact skin. The data obtained in the experiment indicate a weak sensitizing activity of calcium dinitrate. The Limac of the general toxic effect of an aerosol with calcium dinitrate was set at 102 mg/m3 for changes in the functional state of the nervous system and changes in kidney function and coincides with the threshold of irritant effect (Limac) on the respiratory system of experimental animals. Conclusion. Based on the conducted studies and by analogy with the parameters of toxicometry, similar in chemical structure, 5.0 mg/m3 (aerosol, hazard class 3) is proposed as the MPCm.r. of a calcium dihydrate aerosol in the air of the working area (aerosol, hazard class 3), where special protection is required, cleaning of the skin and eyes is required. Ethics. Extract No. 3 of the Meeting of the Local Ethics Committee of Izmerov Research Institute of Occupational Health, dated March 10, 2021.

Villela L.S., Borges I.O., Arantes L.D., Batista F.G., Medeiros D.T., Guimarães Junior M., Mendes L.M., Guimarães Júnior J.B.

Polyanskikh I.S., Gumenyuk A.N., Gordina A.F., Pudov I.A., Yakovlev G.I.

It was defined that structural elements of a building made from electrically conductive concrete may reduce their performance characteristics due to the corrosion environment. The main reasons for that process are supplement corrosion factors such as a wide range of temperature, humidity as well as chemical agents in the environment. In this article results of different properties (mechanical, electrical) of electrically conductive concrete are discussed including their alterations due to sulphate attack. Also, microstructure as well as physical and chemical properties of modified concrete have been considered after being exposed to sulphate attack (Na2SO4) for 112 days. That component has been used for modeling the sulphate attack environment. Compressive strength, rate of the corrosion process, the volume of absorbed SO42– ions from a water-based solution of Na2SO4 was defined in order to analyze the effect of sulphate attack. Scanning electron microscopic investigation, energy dispersive spectroscopy, differential thermal analyses were applied for observing morphology and properties changes of modified samples. To assess the influence of sulphate attack on mineral composite materials the approach was suggested and this method might be useful to foresee the durability of concrete while exposing it to the high corrosion environment. In addition to that, a possible method of protection for electrically conductive concrete from sulphate attack was also considered in the article.

Chaudhari B., Panda B., Šavija B., Chandra Paul S.

Microbiologically induced concrete corrosion (in wastewater pipes) occurs mainly because of the diffusion of aggressive solutions and in situ production of sulfuric acid by microorganisms. The prevention of concrete biocorrosion usually requires modification of the mix design or the application of corrosion-resistant coatings, which requires a fundamental understanding of the corrosion process. In this regard, a state-of-the-art review on the subject is presented in this paper, which firstly details the mechanism of microbial deterioration, followed by assessment methods to characterize biocorrosion and its effects on concrete properties. Different types of corrosion-resistant coatings are also reviewed to prevent biocorrosion in concrete sewer and waste-water pipes. At the end, concluding remarks, research gaps, and future needs are discussed, which will help to overcome the challenges and possible environmental risks associated with biocorrosion.

Fiala L., Pommer V., Böhm M., Scheinherrová L., Černý R.

• Self-heating alkali activated slag mortars (AASMs) with GP are studied. • Degree of formation of electrically conductive GP paths in AAM matrix is analyzed. • Electrical, thermal and mechanical properties are determined. • Links between microstructure and functional properties are assessed. • Model formulas for compressive strength – porosity relations are developed. Alkali activated materials can be considered as eco-friendly substitutes of Portland cement-based composites which leads to their recent increasing use in the construction industry. In this paper, electrical, thermal, and mechanical properties of alkali activated slag mortars containing graphite powder (GP) in various dosage are analyzed and linked with microstructural characteristics. The use of GP in the amount of 8.75 wt% is found to lead to a good self-heating performance of up to 9.9 W. The electrical conductivity of 4.62·10 −2 S/m, compressive strength of 22.7 MPa, flexural strength of 6.9 MPa, and thermal conductivity of 1.36 W/m·K present a satisfactory mix of properties for most self-heating applications.

Wang K., Guo J., Yang L., Zhang P., Xu H.

• The mineralogical phases, morphology, and pore structure of the paste, mortar, and concrete samples were characterized. • The transport properties and durability performance of concrete under ESA depend on its environmental exposure conditions. • The variation in saturation after drying and wetting correlates linearly with dry–wet interval. • The transport of the sulfate ions under the laboratory and field conditions shares similarity. Drying–wetting cycles (DWC) are suspected of influencing the performance of concrete under sulfate attack, but the nature and extent of this influence are still unclear. Therefore, this research concerns understanding the effects of drying–wetting regimes. To this end, pastes, mortars, and concretes were subjected to cyclic drying–wetting with an interval of 12, 24, or 48 h prior to various physical and microstructural analyses. Additionally, drastic drying–wetting conditions with forced drying at 60 °C to reduce relative humidity from 100% to 55% and field-like drying–wetting conditions with gentle stepwise drying in the natural environment were adopted to examine the relationship between the laboratory and field testing. The results indicate that the conditioning regime with a dry–wet ratio of 3:1 and a dry–wet interval of 48 h can be considered a means to accelerate external sulfate attack (ESA) in a short duration and take both reliability and reproducibility into account without overly sacrificing the anticipated filed conditions. The results confirm that the drying–wetting cycle length and the drying mode affect the transport and reaction mechanisms of sulfate ions and the degradation kinetics of sulfate attack. The implications of these findings inform the design of drying–wetting regime for aggressive aqueous environments.

Zaid O., Hashmi S.R., Aslam F., Abedin Z.U., Ullah A.

Graphene oxide can have a massive influence on industries related to concrete and construction in the coming years. Due to the oxygenated capabilities connected to the aromatic structure, it has an improved ability to disperse in mixes in comparison to the other graphene-based materials. Very few researchers have given their idea about the influence of graphene oxide plus fibers on the durability and mechanical behavior of cement-based composites. Five different mixes were developed with utilization of graphene oxide (0%, 0.03%, 0.06%, 0.09% and 0.12% by cement weight) and 2% of steel fibers was added by binder weight. Experimental tests were performed related to mechanical and water permeation characteristics. The concrete mix with 0.12% of graphene oxide has displayed a significant result in terms of mechanical properties and other durability testing in contrast to the other sample mixtures. The permeability and sorptivity of the fiber-strengthened concrete samples in the utilization of graphene oxide were noted to have decreased with increment of graphene oxide content in the mixes in comparison to the reference sample. The synthesized graphene oxide was structurally categorized with the help of FT-IR, EDX, and XRD tests. Microstructural behavior was assessed with the help of XRD spectra on sample cured at 90 days, and the concrete quality was assessed with an ultrasonic pulse velocity test. The study showed that M5 mix (0.12% GO and 2% steel fibers) enhanced compressive and split tensile strength up to 56% and 37%, M5 mix also showed highest average velocity for UPV test and lower values for sorptivity test which indicates improved mechanical properties, durability and reduced porosity. Thus, concrete with GO and steel fibers can be confidently used in building application as sustainable and economic construction material. • Graphene oxide plus steel fibers caused reduction in concrete workability. • Compressive and split tensile strength was improved up to 37% and 56% respectively. • Cost benefit analysis showed M5 mix has high strength per cost while M4 mix has optimum performance for commercial usage.

Rahman M.L., Malakooti A., Ceylan H., Kim S., Taylor P.C.

• Reviewed electrically conductive concrete (ECON) heated pavement system (HPS) technology. • Discussed the material-related factors influencing the performance of ECON HPS. • Analyzed all full-scale ECON HPS projects. • Identified the challenges that ECON HPS technology needs to overcome. Transportation agencies in cold regions often suffer each year economically due to a partial shutdown of their transportation networks during winter storms. Traditional passive ice and snow removal techniques using snowplows, snowblowers, snow shovels and de-icing chemicals are inefficient and hazardous to the environment and pavement. The addition of electrically-conductive fillers (ECFs) such as carbon fibers and steel fibers in a standard concrete mixture reduces electrical resistivity and enhances the resistive heating properties of electrically-conductive concrete (ECON). Under the application of electric voltage, the heat produced from ECON can melt ice and snow accumulated on the pavement. While ECON can be utilized in heated-pavement systems (HPS), field-scale implementation of ECON HPS technology is not yet ubiquitous. This study discusses the challenges that must be overcome to make ECON HPS technology economically attractive to transportation agencies.

Nalon G.H., Santos R.F., Lima G.E., Andrade I.K., Pedroti L.G., Ribeiro J.C., Franco de Carvalho J.M.

• First review focused on sustainable self-sensing composites (SSCs). • Thirteen residues from different sources were analyzed in SSCs production. • The combination of different wastes is a promising alternative to improve the performance of SSC. • Wastes with promising application for production of SSCs were identified. • SSC contribute to the mechanical performance, durability, and sustainability of structures. The construction industry is currently facing the great challenge of applying sustainable materials with suitable mechanical properties and durability performance. Among the different strategies used to meet technical and sustainable criteria, two interesting approaches can be highlighted: the reuse of materials to produce sustainable construction materials and the development of smart concretes for Structural Health Monitoring. The first strategy consists of using recycled materials, co-products, and by-products of industrial processes to replace primary raw materials used to produce blocks, ceramics, mortars, and concrete. The second strategy is associated with the development of multifunctional cementitious and alkali-activated concretes with strain and damage self-sensing properties in response to the growing concerns related to the increase in the durability of civil structures. This paper presents a critical review of previous studies that combine both strategies, i.e., research works investigating smart construction materials that incorporate recycled and waste materials and exhibit self-sensing properties. Sustainable self-sensing composites (SSCs) incorporating different types of recycled and waste materials were presented. These sustainable admixtures provided different benefits to self-sensing composites, such as improvements in the conductive path within the matrices and improvements in the dispersion of other conductive fillers. The effects of silica fume, fly ash, steel slag, red mud, and other recycled materials on the electrical resistivity, strain-sensing properties, and damage-detection properties of SSCs were discussed. Promising SSCs were identified based on comparisons between gauge factor, stress sensibility, linearity, strain amplitude, and stress amplitude of SSCs produced with one single type of waste or combination of various types of wastes. In this sense, SSCs were found to be a viable alternative for modernization and greater sustainability of the construction industry.

Sun X., Li T., Shi F., Liu X., Zong Y., Hou B., Tian H.

The lack of river sand is becoming increasingly serious. In this study, we consider how to use sea sand to prepare innovative construction and building materials with excellent mechanical and durability properties. Sulphate corrosion causes expansion, cracking and spalling of concrete, resulting in the reduction or even loss of concrete strength and cementation force. In this paper, artificial seawater, sea sand, industrial waste, steel fiber and polycarboxylate superplasticizer were used to prepare ultra-high-performance polymer cement mortar (SSUHPC), and the sulphate corrosion mechanism was investigated. The strength and cementation force of mortar on the SSUHPC surface decreased and flaked off with the development of sulphate erosion, and the steel fiber rusted and fell off. A 3D model was established based on X-ray computed tomography (X-CT), and the results showed that SSUHPC maintained excellent internal structural characteristics despite severe sulphate erosion on the surface. Mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were adopted to investigate the sulphate corrosion mechanism of SSUHPC. We found a transition zone within 1–5 mm of the surface of SSUHPC. The Vickers hardness of mortar in this area was increased by 5~15%, and the porosity was reduced to 3.8489%. Obvious structural damage did not occur in this area, but a high content of gypsum appeared. UHPC prepared with seawater sea sand was found to have better sulphate resistance than that prepared with freshwater river sand, which supports the development and utilization of sea sand in concrete.

Peng Y., Meng X., Song F., Xu G.

• Properties of concrete suffering from sulfate and aggressive CO 2 attack were studied. • The content distributions of corrosion products in concrete specimens were examined. • Corrosion process of the specimens undergoing the compound attacks was described. • The corroded specimen undergoing the compound attacks can be divided into 4 layers. The degradation of concrete constructions subjected to acid water containing aggressive carbon dioxide (CO 2 ) and sulfate is primarily attributed to the compound attacks of aggressive CO 2 and sulfate. The performance deterioration of concrete exposed to acid water containing aggressive CO 2 and sodium sulfate were investigated in this paper. The changes in mass, relative dynamic modulus of elasticity, splitting tensile strength, and longitudinal ultrasonic wave of specimens suffering from the coupled effect of aggressive CO 2 and sulfate attacks were used to evaluate the performance degradation of concrete. Moreover, the content and morphology of erosion products formed in the specimens during the process of the attacks were studied via thermogravimetry, X-ray diffraction, and scanning electron microscopy analysis. Then, the corrosion depths and the content distributions of corrosion products of these specimens were examined to explore the corrosion process of concrete. The results showed that the performance degradation of concrete subjected to the coupled attacks were more serious than that of concrete only suffering from one type of attack. According to the content distributions of corrosion products, the corrosion zone of the concrete subjected to the coupled attacks can be divided into 3 layers, namely, the corrosion layer, the dense layer, and the transition layer, where multi-decalcification of hydration products, carbonation and dissolution of carbonates and formation of ettringite, and dissolution of calcium hydroxide and diffusion of sulfate occurred gradually from the external to the internal.

Brown L., Stephens C.S., Allison P.G., Sanchez F.

The use of carbon nanofibers (CNFs) in cement systems has received significant interest over the last decade due to their nanoscale reinforcing potential. However, despite many reports on the formation of localized CNF clusters, their effect on the cement paste micromechanical properties and relation to the mechanical response at the macroscopic scale are still not fully understood. In this study, grid nanoindentation coupled with scanning electron microscopy and energy dispersive spectroscopy was used to determine the local elastic indentation modulus and hardness of a portland cement paste containing 0.2% CNFs with sub-micro and microscale CNF clusters. The presence of low stiffness and porous assemblage of phases (modulus of 15–25 GPa) was identified in the cement paste with CNFs and was attributed primarily to the interfacial zone surrounding the CNF clusters. The CNFs favored the formation of higher modulus C–S–H phases (>30 GPa) in the bulk paste at the expense of the lower stiffness C–S–H. Nanoindentation results combined with a microscale–macroscale upscaling homogenization method further revealed an elastic modulus of the CNF clusters in the range from 18 to 21 GPa, indicating that the CNF clusters acted as compliant inclusions relative to the cement paste.

Yang R., Zhang M., Li Z., He F.

Combined action of external sulfate attack (ESA) and cyclic wetting–drying (CWD) results in the severe durability issue of cement-based materials. A comprehensive microstructural investigation of deterioration mechanism of mortar exposed to ESA and CWD is scarce until now. By means of multiple techniques, the phase evolution, microstructural evolution, pore structure variation and thus the deterioration mechanism of mortars with different water-to-cement ratios (0.3 and 0.5) exposed to ESA and CWD, are investigated in this study. It is found that the amount of portlandite declines fast at the first two wetting–drying cycles and decrease gently in the following cycles, the loss of OH − into external sulfate solution plays a dominant role over uptake of Na + from external sulfate solution during combined action of ESA and CWD; the evolution of pore size distributions of mortars with different water-to-cement ratios exhibit distinct patterns; decalcification of C S H leads to the shrinkage of C S H and collapse of interlayer space and gel pore, responsible for the decreasing amount of interlayer/gel pore at the first 10 wetting–drying cycles and the increase of the amount of interlayer/gel pore at the following 8 cycles; only a few gypsum and thenardite/mirabilite are detected, ettringite is the principal cause of deterioration of mortar subject to ESA and CWD. • A microstructural study on the mortar subject to CWD and ESA is carried out in this study. • The amount of interlayer/gel pore space decreases with CWD at the initial 10 cycles. • AFt is the primary cause for the degradation of the mortar subject to ESA and CWD.

Song H., Yao J., Luo Y., Gui F.

• The strength of pervious concrete subjected to sulfate attack were tested. • A prediction model for the compression strength was promoted. • Compressive strength is related to filling of chemical products and expansion stress. Strength deterioration is one of the primary indicators to reduce the durability of pervious concrete under sulfate attack. This study aimed to establish a chemical–mechanical model to predict the strength evolution. The compressive strength and splitting tensile strength of pervious concrete in three different concentrations of sodium sulfate solution were obtained by experiments. A corrosion coefficient was adopted to evaluate the deterioration of compressive strength. The corrosion coefficient model was developed by considering the pore filling effect of expansion products and the corrosion damage induced by expansion stress. Compared with the experimental results, the developed model could better characterize the deterioration process of pervious concrete. Therefore, the model proposed in this paper provides a more reliable solution for the design and durability life assessment of pervious pavement engineering in sponge city construction projects.

Wang X., Wu Y., Zhu P., Ning T.

The use of conductive concrete is an effective way to address snow and ice accretion on roads in cold regions because of its energy saving and high efficiency without interruption of traffic. Composite conductive concrete was prepared using graphene, carbon fiber, and steel fiber, and the optimum dosage of graphene was explored with resistivity as the criterion. Subsequently, under the conditions of an initial temperature of −15 °C and a wind speed of 20 km/h, the extremely severe snow event environment in cold regions was simulated. The effects of electrode spacing and electric voltage on snow melting performance of conductive concrete slab were explored. Results showed that graphene can significantly improve the conductivity of conductive concrete; the optimal content of graphene was 0.4% of cement mass in terms of resistivity. The snow-melting power of conductive concrete slab decreased with increase in electrode spacing and increased with increase in on-voltage. For an optimal input voltage of 156 V and an optimal electrode spacing of 10 cm, the time required to melt a 24 h snow thickness (21 cm), accumulated during a simulated severe snow event, was only 2 h, which provides an empirical basis for the application of graphene composite conductive concrete to pavement snow melting in cold regions.

Hong S., Choi J., Yuan T., Yoon Y.

There is increased interest in applying electromagnetic (EM) shielding to prevent EM interference, which destroys electronic circuits. The EM shielding’s performance is closely related to the electrical conductivity and can be improved by incorporating conductive materials. The weight of a structure can be reduced by incorporating lightweight aggregates and replacing the steel rebars with CFRP rebars. In this study, the effects of lightweight coarse aggregate and CFRP rebars on the mechanical and electrical characteristics of concrete were investigated, considering the steel fibers’ incorporation. The lightweight coarse aggregates decreased the density and strength of concrete and increased the electrical conductivity of the concrete, owing to its metallic contents. The steel fibers further increased the electrical conductivity of the lightweight aggregate concrete. These components improved the EM shielding performance, and the steel fibers showed the best performance by increasing shielding effectiveness by at least 23 dB. The CFRP rebars behaved similarly to steel rebars because of their carbon fiber content. When no steel fiber was mixed, the shielding effectiveness increased by approximately 2.8 times with reduced spacing of CFRP rebars. This study demonstrates that lightweight aggregate concrete reinforced with steel fibers exhibits superior mechanical and electrical characteristics for concrete and construction industries.

Liu X., Qu M., Nguyen A.P., Dilley N.R., Yazawa K.

• A new thermoelectric cement composite enhanced by graphite and MnO 2. • Simultaneous measurement of thermoelectric properties for cement composites. • Impacts of dry mixing and wet mixing on samples’ TE performance. • Impacts of additives’ concentrations and electrical contact resistance. Thermoelectric cement, the mixture of cement and thermoelectric additives, can convert energy between thermal and electrical forms due to the thermoelectric additives. Potentially, they could be the material for building envelopes to harvest waste heat and/or provide space cooling or heating. When there is a significant difference between indoor and outdoor temperatures, the thermoelectric cement can generate electricity using the temperature gradient. And the same material can cool or heat building space via building envelopes with an electrical input. The research aimed to identify and characterize thermoelectric cement candidates for building envelope applications. The additives used in the studied thermoelectric cement candidates include graphite and MnO 2 . Except for the additives, the study also explored the impact of the two different fabrication methods: wet-mixing and dry-mixing on thermoelectric performance. The images of TE cement candidates taken by scanning electron microscopy and energy dispersive X-ray microscopy visualized the morphology and distribution of additives in the thermoelectric cement composites. The DynaCool Physical Properties Measurement System used in the study simultaneously measured the candidates' thermoelectric properties, including thermal conductivity, electrical conductivity, Seebeck coefficient, and Figure of merit ( ZT ). The test results showed that the thermoelectric cement with the additives of 10% (weight ratio) graphite and 5% MnO 2 has the highest ZT of 6.2 × 10 −6 at 350 K. ZT of the thermoelectric cement is even higher to 10 −5 orders of magnitude when applying a four-probe electrical resistivity method to account for the contact resistance.