Mechanical Properties Of Materials Research Articles

First-principles calculations to investigate Structural, Electronic, mechanical and Optical Properties of SrAlO3 Compound

In this study, density functional theory calculations were used to investigate the structural, electronic, mechanical, and optical properties of SrAlO3 perovskites. Calculations were performed using WEIN2K with the Generalized Gradient Approximation (GGA) and modified Becke-Johnson (MBJ) methods. The present compound shows large band gap around 5.67 eV for GGA method and 6.70 eV for MBJ method. The band structure (BS) and partial density of states (PDOS) reveal the predominant involvement of the oxygen-p orbital in the valence band, while the Al and Sr-s, p and d orbital contribute significantly to the conduction band, that play a significant role in determining the electronic and optical properties. Using the GGA and MBJ methods, the optical properties of SrAlO3 have been determined in terms of optical conductivity, dielectric constant, absorption coefficient, energy loss, optical reflectivity, and refractive index. It has been noted that the features present in the optical absorption spectra obtained experimentally match those of the simulated spectra featuring an oxygen vacancy. We use elastic constants to describe a material's mechanical properties. Under normal conditions, these materials' elastic constants demonstrate their mechanical stability. We meticulously determined the elastic constants by graphing the directional variations of compressibility, Young's modulus, and shear modulus. Our findings indicate that these chemicals have high elastic constants. Furthermore, we collect and interpret the phonon spectra. Complete phonon dispersion simulations validate the dynamic stability of the SrAlO3.

Assessment of hydrogen-induced material degradation using electromagnetic testing technology

The production, transport and use of green hydrogen are key issues for the efficient use of renewable energies. Hydrogen is able to compensate for both temporal and spatial fluctuations that naturally occur in the production and consumption of renewable energies, regardless of weather conditions, and thus can act as an efficient energy storage medium. The use of existing gas pipelines in a dynamically operated pipeline network offers particular potential for the transport of green hydrogen with regard to sustainability, resource conservation and economic efficiency. In this context, dynamic means that pressure fluctuations are permissible to a certain extent in the operation of gas pipelines. However, a hydrogen-induced degradation of the mechanical material properties can lead to brittle fracture and manifest itself in sudden material failure. Such failure must be excluded in safetyrelevant infrastructures. Hence, it would be beneficial to detect fatigued or degraded areas in the material at an early stage, especially in the context of possible increased crack growth rates associated with hydrogen embrittlement. In addition to fatigue data, which are crucial in the calculation and design of gas pipelines, non-destructive inspections are particularly important in subsequent operation to monitor the current condition of the pipelines. Non-destructive testing focuses primarily on defects such as cracks that have already developed or on visible corrosion attack. The fatigue condition, i.e., the probability of crack initiation and crack propagation is hard to evaluate. However, this can be addressed by an electromagnetic test method capable of evaluating the current state of the material. In the presented paper, an electromagnetic test method is presented, which is able to detect and evaluate hydrogen-induced material degradation. In subsequent stages, such a method can then be used as an electromagnetic monitoring system in fatigue tests, thus providing new potential for condition assessment.

Influence of fibril aspect ratio, chemical functionality, and volume fraction on the mechanical properties of cellulose nanofibril materials

AbstractNanocellulose has emerged as a widely utilized building block in nanostructured materials due to its availability, sustainability, large surface area, and high stiffness and aspect ratio. The wet or dry elastoplastic properties of these materials are determined by the fibrils' stiffness, chemical properties, hemicellulose content, and the number of fibril contacts. However, the specific contributions and relative importance of each factor remain unclear. Therefore, this work was devoted to systematically comparing the material properties of gels, aerogels, and wet and dry sheets prepared from CNFs with different aspect ratios, chemical functionality, and hemicellulose content. The fibrils were prepared by chemical and mechanical processing of different pulps. By preserving the native structure as much as possible, higher aspect ratio fibrils can be obtained, which allows for the development of more mechanically robust materials. The results demonstrate that higher aspect ratios lead to more interconnected networks at a lower solids concentration, resulting in a more evenly distributed stress and longer-range stress transfer, yielding stiffer and more ductile materials. The most important finding was that the aspect ratio influences the network formation, resulting in different network topologies. The results were also compared to earlier published data and integrated into a theoretical beam-bending model for a complete elastoplastic description of the network properties, including the influence of fibril aspect ratio and chemical functionality. This information improves our understanding and description of nanofibril networks for which general models have been missing. It can be used to optimize nanofibril preparation and, hence, the resulting eco-friendly materials.

Flexural performance of innovative thin-walled steel–timber composite floor slabs

A floor slab carries and distributes the floor load in a structure and is an important component that affects overall structural performance. Therefore, it is important to investigate the mechanical properties of such materials. In this study, flexural performance tests under static load are conducted for an innovative thin-walled steel–timber composite floor slab, and the failure mode, bearing capacity, stiffness, deflection, and strain development are investigated. The results show that the floor slab can be quickly assembled using self-tapping and wood screws and exhibits good flexural performance. Using ABAQUS finite-element software, the effects of the oriented-strand board (OSB) thickness, thin-walled–steel-plate height, steel strength, and boundary conditions on the flexural performance of composite floor slabs are investigated. Furthermore, based on the EN1995–1-1 code and equal-section conversion principle, the simplified beam-unit model is established for the theoretical calculation of the composite floor slab. The effective bending stiffness is calculated by considering the influence of the slip modulus of the connector, and the stress distribution law of the section is analysed. The results provide a reliable design basis and reference for the application of thin-walled steel–timber composite floor slabs in engineering practice.

A review of new lightweight materials for the automotive industry

The emissions of greenhouse gases caused by the car industry are a substantial contributor to the problem that is the escalation of global warming into a serious crisis. In order to find a solution to this issue, it is essential to enhance the efficiency with which automobiles burn fuel. This goal can be accomplished by replacing heavier components of cars with those made of lighter materials while preserving the same level of safety. This paper discusses some new materials that can be used in vehicles instead of traditional steel, such as high-strength steel, aluminum alloys, magnesium alloys, and carbon fibre. It also determines the most suitable new lightweight materials to be applied to car bodies by comparing the mechanical properties of the various new materials, specifically the strength-to-density ratios of the various new materials. Based on the findings of the study, which compared the ratios of the materials' strengths to their densities, carbon fibre was shown to have superior qualities to those of other materials.

Applications of Bioactive Strontium Compounds in Dentistry

Divalent cations have captured the interest of researchers in biomedical and dental fields due to their beneficial effects on bone formation. These metallic elements are similar to trace elements found in human bone. Strontium is a divalent cation commonly found in various biomaterials. Since strontium has a radius similar to calcium, it has been used to replace calcium in many calcium-containing biomaterials. Strontium has the ability to inhibit bone resorption and increase bone deposition, making it useful in the treatment of osteoporosis. Strontium has also been used as a radiopacifier in dentistry and has been incorporated into a variety of dental materials to improve their radiopacity. Furthermore, strontium has been shown to improve the antimicrobial and mechanical properties of dental materials, promote enamel remineralization, alleviate dentin hypersensitivity, and enhance dentin regeneration. The objective of this review is to provide a comprehensive review of the applications of strontium in dentistry.

Exploring the Effects of E-Multimedia Animation (E-MMA) on Materials Microstructural of Atomic Slip Plane on Materials Mechanical Properties: Conceptual Mastery and Problem-Solving Skills

This study aims to explore the effects of e- Multimedia Animation (E-MMA) on microstructure shift materials on atomic properties of engineering materials with a focus on conceptual mastery and Problem-solving skills. The research sample consisted of 32 JPTM FPTK UPI students who were prospective vocational teachers. The level of difficulty of the engineering materials course varies in each subject, with the majority of students experiencing difficulties in the subject of phase diagrams (68.8%), shifts or movements of atoms and crystal structures (25.0%), and other subjects (6.3%). This research uses research and development methods with qualitative and quantitative approaches. The research instruments used are tests, rubrics, and questionnaires that have been validated by experts. The data processing process is carried out through qualitative and quantitative descriptive analysis, including the percentage of N-gain to measure the improvement of learning outcomes. The results showed that the application of E-MMA to atomic shear plane material resulted in increased mastery of concepts and problem-solving skills. The experimental class using E-MMA achieved an increase in mastery of concepts with an average of 62.82%, while the control class using image media only achieved an increase of 15.52%. This shows that E-MMA is effective in increasing mastery of concepts. In addition, the use of E-MMA also improves problem-solving skills. The experimental class achieved an increase in problem-solving skills by an average of 79.72%, while the control class only achieved an improvement of 15.98%. These results show that E-MMA makes a significant contribution to improving problem-solving skills. Based on these findings, it can be concluded that E-MMA is an effective method for improving mastery of concepts and problem-solving skills in microstructural shift materials in atomic properties of engineering materials. The implementation of E-MMA can help students understand and overcome the difficulties associated with atomic shear planes.

Mechanical properties of rubble pile asteroids (Dimorphos, Itokawa, Ryugu, and Bennu) through surface boulder morphological analysis

Planetary defense efforts rely on estimates of the mechanical properties of asteroids, which are difficult to constrain accurately from Earth. The mechanical properties of asteroid material are also important in the interpretation of the Double Asteroid Redirection Test (DART) impact. Here we perform a detailed morphological analysis of the surface boulders on Dimorphos using images, the primary data set available from the DART mission. We estimate the bulk angle of internal friction of the boulders to be 32.7 ± 2. 5° from our measurements of the roundness of the 34 best-resolved boulders ranging in size from 1.67–6.64 m. The elongated nature of the boulders around the DART impact site implies that they were likely formed through impact processing. Finally, we find striking similarities in the morphology of the boulders on Dimorphos with those on other rubble pile asteroids (Itokawa, Ryugu and Bennu). This leads to very similar internal friction angles across the four bodies and suggests that a common formation mechanism has shaped the boulders. Our results provide key inputs for understanding the DART impact and for improving our knowledge about the physical properties, the formation and the evolution of both near-Earth rubble-pile and binary asteroids.

Perspectives on 2D Materials for Hybrid and Beyond-Si Image Sensor Applications

Abstract The complementary metal–oxide–semiconductor (CMOS) image sensor has become essential and ubiquitous in our daily lives as it is present in almost every pocket. As demand for compact, multifunction, and high-efficiency Internet of Things (IoT) applications continues to rise, novel configuration designs and manufacturing methods, such as neural network integration and 3D stacking have been implemented to enhance the CMOS image sensor’s performance. However, the progress of image sensors based on silicon CMOS technology would eventually be limited by the intrinsic optical, electrical, and mechanical properties of silicon material. This has led to the exploration of two-dimensional materials (2DMs) and the emergence of 2DMs as promising candidates for the next generation of optoelectronic devices. In this article, we discuss the current advancements and challenges associated with silicon CMOS image sensors and the potential benefits of incorporating 2DMs in the image sensor. We highlight three critical opportunities for 2DMs, including Si CMOS/2DMs hybrid structure and direct growth techniques of 2DMs on Si for back-end-of-line (BEOL) integration, 2DMs-based neuromorphic photodetectors and optical neural networks for in-image-sensor-processing, and curved image sensor based on 2DMs photodetectors for bionic detection. With the growing maturity of 2DM technologies, we anticipate that the device scaling and the increase of integration density of 2DM electronics in the image sensor will continue, leading to the development of highly efficient, compact, intelligent, and versatile 2DM image sensors in the near future.

Investigation on the compressive strength of desulfurization gypsum binary cementitious materials with low energy consumption: the utilization enhancement of industrial wastes

Geopolymer, a new low carbon green cementing binder, has widely been used as an alternative to Ordinary Portland cement (OPC), which effectively reduces carbon emissions and industrial solid waste stockpiles on land, also improving solid waste utilization. To raise the utilization of sulphate solid waste and decrease energy consumption, desulphurization gypsum (DG)-based binary cementitious materials were synthesized, and the effects of DG dosage and alkali exciter components on the compressive strength of binary cementitious materials were investigated. In addition, the improvement mechanism of the mechanical properties of binary cementitious materials was revealed by microstructure characterization tools. The results prove that the optimum compressive strength of 52.5 ± 0.5MPa is achieved with a DG dosage of 20%, SiO2/Na2O of 1, water glass dosage of 10% and water-cement ratio of 0.5. Due to the continuous reaction of sulphate in DG with Ca2+ and reactive silicates/aluminosilicates during the curing process, the crystals of ettringite (AFt) are generated and filled the pores of binary cementitious materials and thus furtherly enhancing its compressive strength. And the gel products wrap the AFt that has been filled in the inter-vacancy space on the surface of aluminosilicates already formed at an earlier stage. In summary, ground granulated blast-furnace slag (GGBS) and DG work synergistically to reduce the negative effects of delayed AFt and increase the compressive strength of the geopolymer.

The Quick Determination of a Fibrous Composite’s Axial Young’s Modulus via the FEM

Knowing the mechanical properties of fiber-reinforced composite materials, which are currently widely used in various industrial branches, represents a major objective for designers. This happens when new materials are used that are not yet in production or for which the manufacturer cannot give values. Given the practical importance of this problem, several methods of determining these properties have been proposed, but most of them are laborious and require a long calculation time. And, some of the proposed calculation methods are very approximate, providing only upper and lower limits for these values. Experimental measurements are obviously the optimal solution for solving this problem, but it must be taken into account that this type of method consumes time and material resources. This paper proposes a sufficiently accurate and fast estimation method for determining Young’s modulus for a homogenized fibrous material. Thus, the FEM is used to determine the natural frequencies of a standard bar, for which there are sufficiently precise classical methods to express the engineering constants according to the mechanical properties of the component phases of the homogenized material. In this paper, Young’s modulus is determined for such a material using the relationships that provide the eigenfrequencies for the longitudinal vibrations. With the adopted model, transverse and torsional vibrations are eliminated by blocking the nodes on the surfaces of the bars. In this way, more longitudinal eigenfrequencies can be obtained, so the precision in calculating Young’s modulus is increased.

Mechanics of microblister tests in 2D materials accounting for frictional slippage

The blister test, in which a thin film adhered on a substrate is subject to a uniform transverse pressure from an underlying cavity, is increasingly utilized for the characterization of two-dimensional (2D) materials. Conventional theoretical models of the blister test often assume idealized interfacial conditions such as zero slippage or zero friction. However, experiments indicate that 2D materials can glide over the substrate with a finite interfacial slip resistance. In this study, a theoretical model of blister accounting for frictional slippage at the interface is developed. Subsequent proper normalization makes the model scale independent and serves as a bridge between the actual experiment and molecular dynamics (MD) simulations. On this basis, the inherent differences are revealed between the different interface hypotheses. And especially, to the best of our knowledge, elasticity-adhesion interaction is discussed in detail for the first time under the condition of frictional slippage, enabling a successful amendment to the measurement of interfacial adhesion. Finally, a simplified model is proposed for extracting mechanical properties of 2D materials based on the microblister test.

Photoactivated rose bengal-doped TiO2 nanoparticles modified fifth-generation adhesive on the survival rate of Streptococcus mutants and mechanical properties of tooth-colored restorative material to carious dentin.

Assessment of the antimicrobial, micro tensile bond strength (μTBS), and degree of conversion (DC) of fifth-generation adhesive modified using photoactivated 0.5% rose bengal (RB) and photoactivated RB-doped titanium dioxide nanoparticles (TiO2NPs) in different concentrations (2% and 5%) as compared with the unmodified adhesive bonded to the carious affected dentin (CAD). Forty mandibular molars with caries progression up to the middle third of the dentin, as per the International Caries Detection and Assessment System (ICDAS) score of 4 and 5 were included. Specimens were divided into four groups based on etch and rinse adhesive (ERA) modification group 1: unmodified ERA, group 2: photoactivated 0.5% RB photosensitizer (PS) modified ERA, group 3: photoactivated RB-doped 2 wt% TiO2NPs adhesive, group 4: photoactivated RB-doped 5 wt% TiO2NPs adhesive. Followed by adhesive and composite restoration on the CAD surface. All the specimens were thermocycled and an assessment of μTBS and failure pattern analysis was performed. The antibacterial potency of RB and RB-doped TiO2NPs (2% and 5%) followed by their activation using visible light against Streptococcus mutans (S.mutans) were tested. The survival rate of S.mutans was assessed using the Kruskal-Wallis test. The analysis of μTBS involved the use of ANOVA, followed by a post-hoc Tukey honestly significant difference (HSD) multiple comparisons test. Group 1 (Unmodified ERA) (0.52 ± 0.31 CFU/mL) treated samples unveiled the highest means of bacterial survival and lowest μTBS (11.32 ± 0.63 MPa). Nevertheless, group 4: photoactivated RB-doped 5 wt% TiO2NPs adhesive displayed the lowest outcomes of S.mutans survival (0.11 ± 0.02 CFU/mL) and highest bond strength (18.76 ± 1.45 MPa). The photoactivated RB-doped 2 wt% TiO2NPs in adhesive demonstrated promising enhancements in both μTBS and antibacterial efficacy against S.mutans. However, it is noteworthy that this modification led to a decrease in the DC of the adhesive. RESEARCH HIGHLIGHTS: Unmodified ERA-treated samples unveiled the highest bacterial survival and the lowest μTBS. Photoactivated RB-doped 5 wt% TiO2NPs adhesive displayed the lowest S.mutans survival rate and highest bond strength. DC decreased with an increase in concentration of TiO2.

Maximizing Dental Composite Performance: Strength and Hardness Enhanced by Innovative Polymer-Coated MgO Nanoparticles

IntroductionZein-incorporated magnesium oxide nanoparticles (zMgO NPs) can influence the mechanical properties of dental materials. However, the effect of this addition on the mechanical properties of resin composite has yet to be investigated. The objective of this study was to add various concentrations of zMgO NPs to conventional, flowable, and bulk-fill composite and assess the effect on the compressive strength, flexural strength, and microhardness. Methodology150 samples each of conventional composite, flowable composite, and bulk-fill composite (n=450) were enhanced with concentrations of zMgO NPs at 0%, 0.3%, 0.5%, 1%, and 2% (n=30). 10 samples of each group were randomly allotted to the compressive strength, flexural strength, or hardness test. Characterization of the specimens was performed by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Two-way ANOVA test was used to compare between groups, and one-way ANOVA followed by Tukey's test was done at p=0.05 to determine significance. ResultsCharacterization yielded a uniform distribution of nanoparticles in the matrix and the formation of a new hybrid composite that maintained its properties. Composite of all types enhanced with 0.3% and 0.5% zMgO NPs demonstrated a statistically significant increase in compressive strength, flexural strength, and hardness when compared to the control (p<0.05). The bulk-fill composite with zMgO NPs concentrations of all groups demonstrated a statistically significant increase (p<0.05) in hardness when compared to the control. ConclusionThe modified composites’ compressive strength, flexural strength, and hardness improved or remained consistent. Clinical SignificanceAn improved dental resin composite will enhance the quality of care and patient experience. The augmented strength and hardness of resin composite is desirable in prolonging the durability of the restoration.

Size-dependent vibration analysis of porous 3D-FG microshells in complex thermal environments using a neural network enhanced finite element model

This work aims to investigate the vibration behavior of porous three-directional functionally graded (3D-FG) microshells in thermal environments, where both mechanical and thermal material properties vary along three spatial directions following a power-law distribution, based on the modified couple stress theory (MCST). An isoparametric thermal element is employed for uncoupled heat conduction analysis, followed by dynamic analysis using a penalty solid element with three translation degrees of freedom (DOFs) and three rotation DOFs per node. However, due to the strong nonlinearity of the temperature field in 3D-FG microshells, obtaining exact temperature values at integration points in dynamic analysis requires a pretty dense mesh of the solid element. To overcome this issue, a back propagation (BP) neural network is utilized to predict the temperature field for various gradient indexes, enhancing the efficiency and precision of temperature distribution calculation. Numerical results demonstrate the effectiveness of the neural network enhanced finite element model. Furthermore, the effects of the material length scale parameter (MLSP), temperature difference, and gradient indexes on the natural frequencies are investigated. It is shown that higher structural stiffness weakens the impact of temperature difference on the frequency.

Restoration of exceptional mechanical properties of Al–Cu–Li (AA 2198) alloy post-friction stir processing by recovery of T1 precipitates through controlled temper conditions

Friction stir processing (FSP) is considered to be an effective technique to improve the mechanical properties of metallic materials through grain refinement. However, the fine-grained Al–Cu–Li (AA2198) alloy exhibits a drastic reduction in strength post-FSP as compared to its peak aged temper condition due to the dissolution of its primary strengthening phase, T1 (Al2CuLi) during processing. The present study is aimed at recovering T1 precipitates, thereby restoring the alloy strength. The evolution of microstructure in both the base alloy and FSP alloy subjected to different temper conditions was examined by detailed electron microscopy and was analyzed through a differential scanning calorimetry study. The mechanical properties of the alloy were evaluated by Vickers hardness measurements and tensile testing at room temperature. Experimental findings reveal that the direct aging treatment is ineffective in recovering T1 in FSP alloy due to the delayed precipitation kinetics. However, prior cold working led to the recovery of substantial amounts of T1 during further aging of the FSP alloy. The variation in hardness and tensile properties were in alignment with the precipitation states, and the exceptional mechanical properties were restored in the FSP alloy with the recovery of T1 by cold work prior to aging. The strength modeling indicated that the experimental yield strength after T1 recovery is lower than the predicted value, and these are attributed to the incomplete recovery of the T1 due to trapping of the solute in Cu-rich Al based intermetallics. To dissolve the intermetallics solution treatment was performed after FSP, but it led to significant abnormal grain growth (AGG) and is analyzed using Humphrey’s framework.

Experimental analysis of the piezomagnetic behavior of double-shear bolted connections of wire and arc additively manufactured steel

ABSTRACT In this paper, the piezomagnetic behaviour of WAAM double-shear connection specimens were investigated. It aims to develop a damage monitoring method based on piezomagnetic effect for WAAM steel bolted connections. Eight WAAM steel coupons with two different print layer orientations were fabricated to measure the mechanical properties of WAAM materials. A total of 32 WAAM double-shear bolted connection specimens with two print layer orientations were designed to analyse the structural properties of WAAM members. A magnetic probe was used to monitor the variations of the piezomagnetic field. The evolutions of piezomagnetic field of transversal and longitudinal WAAM coupons were compared and analysed. Notably, it is found that piezomagnetic field manifests anisotropy consistent with the mechanical properties. The characteristics of five failure modes including net section tension, end-splitting, shear-out, bearing, block shear were discussed. The correlation between the magnetic field–displacement curve and the load-displacement curve was systematically examined. The characteristics of magnetic field of specimens failing by bearing were emphatically explored. The results show that bearing failure can be distinguished from other failure modes by monitoring the magnetic field. In addition, the evolution of magnetic field serves as a predictor of the ultimate capacity and failure of double-shear bolted connections.

Study of Various Mechanical Properties of Maize (Zea mays) as Influenced by Moisture Content

The mechanical properties of agricultural materials influence not only the loads occurring inside agricultural silos, but also the design of several types of post-harvest machinery. The loads generated by these materials inside silos can be predicted with silo calculation methodologies from their mechanical properties. It has been known for many years that these properties are highly dependent on the moisture content of the material. However, to date, there are not many studies focused on its determination. The goal of this research is the determination of the internal friction angle, apparent cohesion, angle of dilatancy and apparent specific weight of maize when different moisture contents are applied. The equipment used for this study consisted mainly of direct shear and oedometer assay apparatus. The maize samples used were moistened using a climatic chamber. Moisture contents applied to maize samples ranged from 9.3% to 17.4%. Results similar to those provided by other authors were obtained for the internal friction angle, apparent cohesion and apparent specific weight. On the other hand, the values obtained for the dilatancy angle of maize as a function of moisture content could not be compared because nothing has been published so far. The values obtained for this parameter overlap with those published for this material under ambient conditions. In addition, for the samples tested, these results did not allow confirming the existence of a direct relationship between the dilatancy angle and the moisture content. Finally, the increase in moisture content led to an increase in apparent specific weight, which differed from that published in the literature. The values provided here can be used for the optimization of storage and handling structures for granular agricultural materials.

Ensemble learning evaluation of mechanical property for mining waste cemented backfill

Processing the large amount of waste rock generated from mining into backfill materials enables the resource utilization of waste materials. Additionally, the mechanical properties of backfill materials influence the stability of overlying strata. Therefore, this study established a large-scale dataset of coal gangue-based and tailing-based backfill materials. Three novel ensemble learning models were developed to evaluate the nonlinear effects of 29 dimensional factors on the mechanical properties of backfill material. Additionally, factors like material type, preparation method, and measurement error can cause discrepancies in mechanical properties, affecting evaluation accuracy. Consequently, this paper constructed SVR fusion models using three ensemble learning methods to enhance robustness on differentiated data. It investigated the impacts of ensemble methods, ensemble levels, and perturbation levels on the model. The study found that the Bagging-ensembled SVR performed optimally, with R2, MAE, and RMSE of 0.951, 0.369, and 0.560, respectively, exhibiting better robustness on perturbed datasets. This study contributes to resource utilization in mining waste.

Circular Economy of Construction and Demolition Waste for Nanocomposite Cement: XRD, NMR, Vickers, Voltammetric and EIS Characterization

In this paper, we present the structural, mechanical and electrical properties of composite cement materials that can be widely used as substituent for cement. We start with the characterization of a composite cement sample using an analysis of X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectra. The measurements of the Vickers hardness, cyclic and sweep linear voltammetry and electrochemical impedance spectroscopy (EIS) of composite cement materials were also recorded. This study compared the effect of the different nanocomposites added to cement on the mitigation of the alkali–silica reaction, which is responsible for the swelling, cracking and deleterious behavior of the material. The enhancement in Vickers hardness was more pronounced for composite cement materials. In contrast, the values of Vickers hardness decreased for the composite cement containing mortar and the control sample, suggesting that the long-term performance of cement was compromised. In order to obtain information about the bulk resistance of the composite cement material, electrochemical impedance spectroscopy (EIS) data were employed. The results suggest that for composite cement materials, there is an improvement in bulk electrical resistance, which can be attributed to the lower amounts of cracks and swelling due to lower expansion. In the control sample, a reduction in the bulk resistance suggests the formation of microcracks, which cause the aging and degradation of the material. The intersection of arcs in the EIS spectrum of the mixed composite cement sample gradually increased by an alkaline exposure of up to 21 days and finally shifted towards a low value of high frequency with an increase in alkaline exposure of up to 28 days.