Materials

15 pages, 3415 KB

Open AccessArticle

The Influence of Particle Shape and Surface Roughness of Fine Aggregates on the Technological Properties of Glass-Fiber-Reinforced Thin-Layer Concrete

by Ramune Zurauskiene, Asta Kičaitė and Rimvydas Moceikis

Materials 2026, 19(1), 214; https://doi.org/10.3390/ma19010214 - 5 Jan 2026

Viewed by 267

Abstract

Various methods for classifying and evaluating the shape, size, and surface texture of sand particles are examined, highlighting their impact on concrete mixture properties. This study emphasizes the role of particle morphology in determining concrete workability and segregation, particularly in glass-fiber-reinforced (GRC) thin-layer [...] Read more.

Various methods for classifying and evaluating the shape, size, and surface texture of sand particles are examined, highlighting their impact on concrete mixture properties. This study emphasizes the role of particle morphology in determining concrete workability and segregation, particularly in glass-fiber-reinforced (GRC) thin-layer concrete for building facade panels. The effects of different aggregate types on concrete workability and segregation are analyzed, showing that aggregates with spherical particles and a lower elongation index improve mixture consistency and reduce segregation. Three types of fine aggregates were used (instead of quartz sand in the mixtures, natural sand and granite screenings were chosen, which would be a sustainable alternative to quartz sand), and thin-layer glass-fiber-reinforced concrete using aggregates of different shapes was characterized by layering the mixture. The workability and segregation of fine-grained fiberglass-reinforced concrete mixtures depend on the aggregate particles’ shape. Up to 50% of quartz sand can be replaced with granite siftings or natural sand, as measured by the segregation index, as calculated according to the method proposed in this paper. Increasing the amount of natural sand from 10% to 50% also increases the segregation index from 1.9 to 2.6, and when using granite sifting aggregates, it rises from 2.6 to 3.5. Aggregates with spherical particles are more suitable for this thin-layer GRC concrete, if we examine the consistency parameters of fresh concrete and the possibilities of working with it in real production conditions. Full article

(This article belongs to the Section Construction and Building Materials)

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23 pages, 7506 KB

Open AccessArticle

Enhancing Tensile Performance of Lithium Slag Geopolymers Using Hybrid Fibers and Modified Multi-Walled Carbon Nanotubes

by Qing Li, Chong Deng, Yali Hu, Mingxing Luo, Daopei Zhu and Cai Wu

Materials 2026, 19(1), 213; https://doi.org/10.3390/ma19010213 - 5 Jan 2026

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Abstract

This study investigates the synergistic effects of hybrid fibers and functionalized multi-walled carbon nanotubes (MWCNTs) on the mechanical and microstructural properties of lithium slag–based geopolymers (FL-EGC). Unlike conventional studies that focus on single reinforcement strategies, this work combines nanoscale modification with macroscale fiber [...] Read more.

This study investigates the synergistic effects of hybrid fibers and functionalized multi-walled carbon nanotubes (MWCNTs) on the mechanical and microstructural properties of lithium slag–based geopolymers (FL-EGC). Unlike conventional studies that focus on single reinforcement strategies, this work combines nanoscale modification with macroscale fiber reinforcement to overcome the inherent brittleness of geopolymers. Results show that while hybrid fibers and MWCNTs reduce flowability, the incorporation of 2.5% PVA, 1.0% steel fibers, and 0.15% MWCNTs yielded the best balance of performance, improving ultimate tensile stress by 12.7%, strain by 69.2%, and specific fracture energy by 78.2%. Microstructural analysis confirmed that MWCNTs enhanced crack-bridging and matrix densification, while hybrid fibers improved strength and ductility. These findings demonstrate a novel reinforcement pathway for developing sustainable, high-performance geopolymers from industrial by-products, providing both theoretical insights and practical guidance for green construction materials. Full article

(This article belongs to the Special Issue Geopolymers and Fiber-Reinforced Concrete Composites (Second Edition))

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18 pages, 6545 KB

Open AccessArticle

The Impact of 3D Printing on Mortar Strength and Flexibility: A Comparative Analysis of Conventional and Additive Manufacturing Techniques

by Tomas Gil-Lopez, Alireza Amirfiroozkoohi, Mercedes Valiente-Lopez and Amparo Verdu-Vazquez

Materials 2026, 19(1), 212; https://doi.org/10.3390/ma19010212 - 5 Jan 2026

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Abstract

With the rise in additive manufacturing in construction, particularly 3D printing using extrusion-based mortars, there is an increasing need to optimize material properties. This study compares the mechanical performance of mortar specimens produced by traditional casting and 3D printing, with a focus on [...] Read more.

With the rise in additive manufacturing in construction, particularly 3D printing using extrusion-based mortars, there is an increasing need to optimize material properties. This study compares the mechanical performance of mortar specimens produced by traditional casting and 3D printing, with a focus on flexural behavior. A high-durability mortar with very low chloride and sulfate content, which produces less CO₂ than standard Portland cement, was used. This study also explores the impact of varying water–cement (w/c) ratios to obtain a valid mix for both fabrication methods. The results show that the samples obtained by traditional processes and those produced through 3D printing exhibit distinctly different behaviors under bending stresses. In the case of the molded samples, the maximum stress ranged from 1.23 to 1.78 MPa, indicating good strength and uniformity within these materials. In contrast, the 3D-printed samples showed higher values but with greater variation, ranging between 2.77 and 3.76 MPa. This variation highlights the influence of the fabrication technique in 3D printing, which may contribute to either the superiority or limitations of these samples. In terms of deformation, molded specimens exhibited brittle failure with limited post-peak energy dissipation (0.11–0.22 kN.mm), whereas 3D-printed samples displayed a mixed brittle–ductile response and enhanced energy absorption (1.70–2.82 kN.mm). These findings suggest that traditionally obtained specimens are suitable for applications requiring predictable stiffness, while 3D-printed mortars are advantageous for applications demanding greater flexibility and energy absorption. Full article

(This article belongs to the Special Issue Preparation and Properties of New Cementitious Materials (2nd Edition))

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21 pages, 7512 KB

Open AccessArticle

Controlled Synthesis and Formation Mechanism of Uniformly Sized Spherical CeO₂ Nanoparticles

by Jiayue Xie, Kai Feng, Rui Ye, Maokui Wang, Yunci Wang, Xing Fan and Renlong Liu

Materials 2026, 19(1), 211; https://doi.org/10.3390/ma19010211 - 5 Jan 2026

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Abstract

As the core abrasive in chemical mechanical polishing (CMP) processes, the morphology, size uniformity, and chemical reactivity of CeO₂ nanoparticles (NPs) are crucial factors determining the surface precision and yield of devices. In this work, a KNO₃–LiNO₃ eutectic molten [...] Read more.

As the core abrasive in chemical mechanical polishing (CMP) processes, the morphology, size uniformity, and chemical reactivity of CeO₂ nanoparticles (NPs) are crucial factors determining the surface precision and yield of devices. In this work, a KNO₃–LiNO₃ eutectic molten salt was used as the reaction medium. By systematically adjusting key processing parameters (such as the type of cerium source, the species and dosage of surfactants, and calcination conditions), the regulatory effects of these factors on particle growth mechanisms were clarified. This adjustment enabled the controlled synthesis of spherical CeO₂ NPs with customized morphology, particle size, and surface defect states. The multi-stage reaction process of the precursor during calcination was identified by applying thermal analysis techniques, including TG-DSC and TG-FTIR. This process includes dehydration, ion exchange, and thermal decomposition. Microstructural analysis shows that the type and dosage of the cerium source and template agent significantly affect the uniformity of particle size and spherical morphology. Moreover, by using an optimized process with a heating rate of 6 °C/min and maintaining at 400 °C for 3 h, spherical CeO₂ NPs with an average particle size of 60 nm, uniform size distribution, and high sphericity were successfully synthesized via a single-step calcination process. Based on these findings, a further proposal was put forward regarding a crystal growth mechanism mediated by micelle-directed assembly and oriented attachment. This method only requires a single calcination step, has mild reaction conditions, and involves a simple process without the need for specialized equipment—features that show great potential for scalable production. It provides both a theoretical basis and experimental support for the controlled preparation of high-performance CeO₂ abrasives. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

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28 pages, 6311 KB

Open AccessArticle

Machine Learning-Assisted Optimisation of the Laser Beam Powder Bed Fusion (PBF-LB) Process Parameters of H13 Tool Steel Fabricated on a Preheated to 350 ^∘C Building Platform

by Katsiaryna Kosarava, Paweł Widomski, Michał Ziętala, Daniel Dobras, Marek Muzyk and Bartłomiej Adam Wysocki

Materials 2026, 19(1), 210; https://doi.org/10.3390/ma19010210 - 5 Jan 2026

Viewed by 622

Abstract

This study presents the first application of Machine Learning (ML) models to optimise Powder Bed Fusion using Laser Beam (PBF-LB) process parameters for H13 steel fabricated on a 350 °C preheated building platform. A total of 189 cylindrical specimens were produced for training [...] Read more.

This study presents the first application of Machine Learning (ML) models to optimise Powder Bed Fusion using Laser Beam (PBF-LB) process parameters for H13 steel fabricated on a 350 °C preheated building platform. A total of 189 cylindrical specimens were produced for training and testing machine learning (ML) models using variable process parameters: laser power (250–350 W), scanning speed (1050–1300 mm/s), and hatch spacing (65–90

μ

m). Eight ML models were investigated: 1. Support Vector Regression (SVR), 2. Kernel Ridge Regression (KRR), 3. Stochastic Gradient Descent Regressor, 4. Random Forest Regressor (RFR), 5. Extreme Gradient Boosting (XGBoost), 6. Extreme Gradient Boosting with limited depth (XGBoost LD), 7. Extra Trees Regressor (ETR) and 8. Light Gradient Boosting Machine (LightGBM). All models were trained using the Fast Library for Automated Machine Learning & Tuning (FLAML) framework to predict the relative density of the fabricated samples. Among these, the XGBoost model achieved the highest predictive accuracy, with a coefficient of determination

R^{2} = 0.977

, mean absolute percentage error MAPE = 0.002, and mean absolute error MAE = 0.017. Experimental validation was conducted on 27 newly fabricated samples using ML predicted process parameters. Relative densities exceeding 99.6% of the theoretical value (7.76 g/cm³) for all models except XGBoost LD and KRR. The lowest MAE = 0.004 and the smallest difference between the ML-predicted and PBF-LB validated density were obtained for samples made with LightGBM-predicted parameters. Those samples exhibited a hardness of 604 ± 13 HV0.5, which increased to approximately 630 HV0.5 after tempering at 550 °C. The LightGBM optimised parameters were further applied to fabricate a part of a forging die incorporating internal through-cooling channels, demonstrating the efficacy of machine learning-guided optimisation in achieving dense, defect-free H13 components suitable for industrial applications. Full article

(This article belongs to the Special Issue Multiscale Design and Optimisation for Metal Additive Manufacturing)

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27 pages, 7522 KB

Open AccessArticle

Prediction of the Unconfined Compressive Strength of One-Part Geopolymer-Stabilized Soil Under Acidic Erosion: Comparison of Multiple Machine Learning Models

by Jidong Zhang, Guo Hu, Junyi Zhang and Jun Wu

Materials 2026, 19(1), 209; https://doi.org/10.3390/ma19010209 - 5 Jan 2026

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Abstract

This study employed machine learning to investigate the mechanical behavior of one-part geopolymer (OPG)-stabilized soil subjected to acid erosion. Based on the unconfined compressive strength (UCS) data of acid-eroded OPG-stabilized soil, eight machine learning models, namely, Adaptive Boosting (AdaBoost), Decision Tree (DT), Extra [...] Read more.

This study employed machine learning to investigate the mechanical behavior of one-part geopolymer (OPG)-stabilized soil subjected to acid erosion. Based on the unconfined compressive strength (UCS) data of acid-eroded OPG-stabilized soil, eight machine learning models, namely, Adaptive Boosting (AdaBoost), Decision Tree (DT), Extra Trees (ET), Gradient Boosting (GB), Light Gradient Boosting Machine (LightGBM), Random Forest (RF), Support Vector Machine (SVM), and eXtreme Gradient Boosting (XGBoost), along with hyper-parameter optimization by Genetic Algorithm (GA), were used to predict the degradation of the UCS of OPG-stabilized soils under different durations of acid erosion. The results showed that GA-SVM (R² = 0.9960, MAE = 0.0289) and GA-XGBoost (R² = 0.9961, MAE = 0.0282) achieved the highest prediction accuracy. SHAP analysis further revealed that solution pH was the dominant factor influencing UCS, followed by the FA/GGBFS ratio, acid-erosion duration, and finally, acid type. The 2D PDP combined with SEM images showed that the microstructure of samples eroded by HNO₃ was marginally denser than that of samples eroded by H₂SO₄, yielding a slightly higher UCS. At an FA/GGBFS ratio of 0.25, abundant silica and hydration products formed a dense matrix and markedly improved acid resistance. Further increases in FA content reduced hydration products and caused a sharp drop in UCS. Extending the erosion period from 0 to 120 days and decreasing the pH from 4 to 2 enlarged the pore network and diminished hydration products, resulting in the greatest UCS reduction. The results of the study provide a new idea for applying the ML model in geoengineering to predict the UCS performance of geopolymer-stabilized soils under acidic erosion. Full article

(This article belongs to the Section Construction and Building Materials)

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15 pages, 6959 KB

Open AccessArticle

Densification Behavior and Microstructure of Nickel Aluminum Bronze Alloy Fabricated by Laser Powder Bed Fusion

by Yizhe Huang, Guanjun Fu, An Wang, Zhongxu Xiao, Jinfeng Sun, Jun Wang and Xiaojia Nie

Materials 2026, 19(1), 208; https://doi.org/10.3390/ma19010208 - 5 Jan 2026

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Abstract

Nickel–Aluminum–Bronze (NAB) has gained significant attention in marine applications due to its excellent corrosion resistance and has shown growing potential for laser powder bed fusion (L-PBF) additive manufacturing. However, research on the fabrication of NAB alloys using L-PBF remains relatively limited. In this [...] Read more.

Nickel–Aluminum–Bronze (NAB) has gained significant attention in marine applications due to its excellent corrosion resistance and has shown growing potential for laser powder bed fusion (L-PBF) additive manufacturing. However, research on the fabrication of NAB alloys using L-PBF remains relatively limited. In this study, fully dense NAB samples were successfully fabricated through L-PBF process parameter optimization. The microstructural evolution and mechanical properties of both as-built and annealed L-PBF samples were systematically investigated and compared with those of traditionally cast NAB. The results reveal that the as-built L-PBF specimens primarily consist of columnar β′ grains, with the α phase distributed along the grain boundaries and a small amount of κ phase precipitated within the β′ matrix, distinctly different from the cast microstructure characterized by a columnar α-phase matrix with precipitated β′ and κ phases. After annealing at 675 °C for 6 h, the β′ phase in both methods decomposed into α + κ phases, and the original columnar structure in the L-PBF specimens transformed into a dendritic morphology. Compared to the cast samples, the L-PBF-produced NAB alloy exhibited significantly enhanced yield strength, tensile strength, and microhardness, attributable to rapid solidification during the L-PBF process. Following annealing, the yield strength and elongation increased by 12.8% and 184.4%, respectively, compared to the as-built condition, resulting from the decomposition of the martensitic phase into α + κ phases and further grain refinement. Full article

(This article belongs to the Section Metals and Alloys)

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17 pages, 2843 KB

Open AccessArticle

Synthesis and Characterization of Water-Soluble EDTA-Crosslinked Poly-β-Cyclodextrins Serving as Ion-Complexing Drug Carriers

by Zuzanna Podgórniak, Witold Musiał, Michał J. Kulus, Dominika Łacny, Aleksandra Budnik and Tomasz Urbaniak

Materials 2026, 19(1), 207; https://doi.org/10.3390/ma19010207 - 5 Jan 2026

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Abstract

Water-soluble poly-β-cyclodextrins (PCDs), crosslinked with ethylenediaminetetraacetic acid dianhydride (EDTADA), were synthesized at varying β-CD:EDTADA molar ratios (1:6, 1:9, 1:12, 1:15) to develop multifunctional nanocarriers with the ability to complex drugs, polymers, and ions. All PCDs exhibited nanometric particle sizes (14 to 28 nm), [...] Read more.

Water-soluble poly-β-cyclodextrins (PCDs), crosslinked with ethylenediaminetetraacetic acid dianhydride (EDTADA), were synthesized at varying β-CD:EDTADA molar ratios (1:6, 1:9, 1:12, 1:15) to develop multifunctional nanocarriers with the ability to complex drugs, polymers, and ions. All PCDs exhibited nanometric particle sizes (14 to 28 nm), negative zeta potential (−18 to −27 mV), and adjustable content of free carboxyl groups controlled by crosslinker ratio. Functional evaluations demonstrated effective Ca²⁺ chelation and a linear inclusion complexation profile with acyclovir, but not with naproxen, highlighting pH-dependent solubility effects. Additionally, PCDs successfully formed polyelectrolyte complexes with poly-L-lysine, indicating their potential as components of advanced drug delivery systems. Among the analyzed variants, PCD 1:6 showed reduced yields, fewer reactive groups, and diminished ion-binding capacity compared to formulations with higher crosslinker content. These findings underscore the importance of crosslinking density in modulating physicochemical and functional properties and support the potential of EDTA-crosslinked PCDs as versatile platforms for advanced, ion-sensitive biomedical applications. Full article

(This article belongs to the Special Issue Design and Development of Polymer-Based Drug Carriers for Biomedical Applications)

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35 pages, 6397 KB

Open AccessReview

A Review of Femtosecond Laser Processing for Sapphire

by Chengxian Liang, Jiecai Feng, Hongfei Liu, Yanning Sun, Yilian Zhang and Yingzhong Tian

Materials 2026, 19(1), 206; https://doi.org/10.3390/ma19010206 - 5 Jan 2026

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Abstract

Sapphire (α-Al₂O₃) has been widely used in high-power lasers, optical windows, semiconductor substrates, radomes, and other applications due to its exceptional optical properties, high hardness, excellent chemical stability, and thermal resistance. However, machining sapphire poses significant challenges because of [...] Read more.

Sapphire (α-Al₂O₃) has been widely used in high-power lasers, optical windows, semiconductor substrates, radomes, and other applications due to its exceptional optical properties, high hardness, excellent chemical stability, and thermal resistance. However, machining sapphire poses significant challenges because of the material’s high hardness and brittleness. Traditional mechanical and chemical–mechanical machine methods often fail to meet the processing requirements for micro and nanoscale structures. Recently, the use of femtosecond lasers—with ultra-short pulses and extremely high peak power—has allowed for the precise machining of sapphire with minimal thermal damage, a method akin to cold processing. Femtosecond laser processing offers significant advantages in fabricating three-dimensional micro- and nanoscale structures, surface and internal modification, optical waveguide writing, grating fabrication and dissimilar materials welding. Thus, this paper systematically reviewed the research progress in femtosecond laser processing of sapphire, covering technical approaches such as ablation, hybrid processing and direct writing micro- and nanoscale fabrication. The capability of femtosecond laser processing to modulate sapphire’s optical properties, wettability and mechanical and chemical characteristics were discussed in detail. The current challenges related to efficiency, cost, process standardization and outlines future development directions, including high-power lasers, parallel processing, AI optimization and multifunctional integration were also analyzed. Full article

(This article belongs to the Special Issue Advances in Materials Processing (4th Edition))

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16 pages, 2638 KB

Open AccessArticle

Application of Machine Learning Models in Predicting Vibration Frequencies of Thin Variable Thickness Plates

by Łukasz Domagalski and Izabela Kowalczyk

Materials 2026, 19(1), 205; https://doi.org/10.3390/ma19010205 - 5 Jan 2026

Viewed by 290

Abstract

This study investigates the application of machine learning (ML) techniques for predicting vibration frequencies of thin rectangular plates with variable thickness. Traditional optimization methods, such as genetic algorithms, require repeated solutions of the plate vibration eigenproblem using finite element (FE) analysis, which is [...] Read more.

This study investigates the application of machine learning (ML) techniques for predicting vibration frequencies of thin rectangular plates with variable thickness. Traditional optimization methods, such as genetic algorithms, require repeated solutions of the plate vibration eigenproblem using finite element (FE) analysis, which is computationally expensive. To reduce this cost, a surrogate model based on artificial neural networks (ANNs) is proposed as an efficient alternative. The dataset includes variations in plate geometry, boundary conditions, and thickness distribution, encoded numerically for model training. ANN architecture and hyperparameters—such as the number of hidden layers, neurons per layer, and activation functions—were systematically tuned to achieve high prediction accuracy while avoiding overfitting. Data preprocessing steps, including standardization and scaling, were applied to improve model stability. Performance was evaluated using metrics such as RMSE and R². The results demonstrate that ANNs can accurately predict eigenvalues with significantly reduced computational effort compared to FE analysis. This approach offers a practical solution for integrating machine learning into structural optimization workflows. Full article

(This article belongs to the Special Issue Advances in Machine Learning for the Prediction of Construction Materials Properties)

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20 pages, 2067 KB

Open AccessArticle

Modeling the Dynamics of Electric Field-Assisted Local Functionalization in Two-Dimensional Materials

by Fernando Borrás, Julio Ramiro-Bargueño, Óscar Casanova-Carvajal, Alicia de Andrés, Sergio J. Quesada and Ángel Luis Álvarez

Materials 2026, 19(1), 204; https://doi.org/10.3390/ma19010204 - 5 Jan 2026

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Abstract

Electric field-assisted local functionalization of materials is a resist-free technique generally applied at the nanoscale, which has been understood within the paradigm of the water meniscus. Using a home-made prototype the authors applied this technique at scales compatible with the biosensor industry (tens [...] Read more.

Electric field-assisted local functionalization of materials is a resist-free technique generally applied at the nanoscale, which has been understood within the paradigm of the water meniscus. Using a home-made prototype the authors applied this technique at scales compatible with the biosensor industry (tens of microns). However, interpreting these results requires a different paradigm. The expansion of the oxidized region over time in two-dimensional materials under a localized electric field is modeled from first physical principles. Boltzmann statistics is applied to the oxyanion incorporation at the perimeter of the oxidized zone, and a new general relation between oxide radius and time is formulated. It includes the reduction in the energy barrier due to the field effect and its dependence on the oxide radius. To gain insight into this dependence whatever the layers structure, 2D material involved, or electrical operating conditions, simple structures based on multilayer stacks representing the main constituents are proposed, where the Poisson equation is solved using finite element calculations. This enables to derive energy barriers for oxyanion incorporation at varying spot radii which are consistent with those resulting from fitting experimental data. The reasonable agreement obtained provides researchers with a new tool to predict the evolution of local functionalization of 2D layers as a function of the following fabrication parameters: time, applied voltage, and relative humidity, solely based on materials properties. Full article

(This article belongs to the Section Materials Simulation and Design)

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22 pages, 6583 KB

Open AccessArticle

Flexural Fracture Behavior and Mechanical Properties of SAP-PVA Fiber-Reinforced Concrete

by Xiaozhu Hu, Yanjun Wang, Faxiang Xie and Wenhao Cao

Materials 2026, 19(1), 203; https://doi.org/10.3390/ma19010203 - 5 Jan 2026

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Abstract

To investigate the fracture behavior of super-absorbent polymer (SAP) internally cured polyvinyl alcohol (PVA) fiber-reinforced concrete (SAP-PVAC), three-point bending tests were carried out. This study systematically examined the effects of (1) PVA fiber content and (2) initial crack-depth-to-beam-height ratios (a₀/ [...] Read more.

To investigate the fracture behavior of super-absorbent polymer (SAP) internally cured polyvinyl alcohol (PVA) fiber-reinforced concrete (SAP-PVAC), three-point bending tests were carried out. This study systematically examined the effects of (1) PVA fiber content and (2) initial crack-depth-to-beam-height ratios (a₀/D) on the failure modes, fracture toughness (K_IC), and residual flexural tensile strength (f_R,1) of SAP-PVAC beams. The test results demonstrate that SAP particles have a weakening effect on concrete strength (reduce about 6%). Still, the addition of PVA fibers can effectively improve the crack-resistance performance of SAP-PVAC and significantly increase the residual flexural tensile strength by 4.5–42%. The softening performance of the concrete is affected by the initial crack-height ratio. An increase in a₀/D leads to an obvious increase in the crack opening displacement but has little impact on the fracture toughness, while the fracture energy shows a downward trend. SEM microscopic analysis reveals that the synergistic effect of SAP and PVA fibers exhibits a positive promoting effect on the toughening and crack resistance of SAP-PVAC specimens. These results establish a theoretical framework for SAP-PVAC fracture assessment and provide actionable guidelines for its shrinkage-crack mitigation structure engineering applications. Full article

(This article belongs to the Special Issue Reinforced Concrete: Mechanical Properties and Materials Design)

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20 pages, 14945 KB

Open AccessArticle

Study on the Transport Law and Corrosion Behavior of Sulfate Ions of a Solution Soaking FA-PMPC Paste

by Yuying Hou, Qiang Xu, Tao Li, Sha Sa, Yante Mao, Caiqiang Xiong, Xiamin Hu, Kan Xu and Jianming Yang

Materials 2026, 19(1), 202; https://doi.org/10.3390/ma19010202 - 5 Jan 2026

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Abstract

To study the sulfate corrosion behavior of potassium magnesium phosphate cement (PMPC) paste, the sulfate content, strength, and length of PMPC specimens were measured at different corrosion ages under 5% Na₂SO₄ solution soaking conditions, and the phase composition and microstructure [...] Read more.

To study the sulfate corrosion behavior of potassium magnesium phosphate cement (PMPC) paste, the sulfate content, strength, and length of PMPC specimens were measured at different corrosion ages under 5% Na₂SO₄ solution soaking conditions, and the phase composition and microstructure were analyzed. The conclusion is as follows: In PMPC specimens subjected to one-dimensional SO₄²⁻ corrosion, the relation between the diffusion depth of SO₄²⁻ (h) and the SO₄²⁻ concentration (c (h, t)) can be referred by a polynomial very well. The sulfate diffusion coefficient (D) of PMPC specimens was one order of magnitude lower than Portland cement concrete (on the order of 10⁻⁷ mm²/s). The surface SO₄²⁻ concentration c (0, t), the SO₄²⁻ computed corrosion depth h₀₀, and D of FM2 specimen containing 20% fly ash (FA) were all less than those of the FM0 specimen (reference). At 360-day immersion ages, the c (0, 360 d) and h₀₀ in FM2 were obviously smaller than those in FM0, and the D of FM2 was 64.2% of FM0. The strengths of FM2 specimens soaked for 2 days (the benchmark strength) were greater than those of FM0 specimens. At 360-day immersion ages, the residual flexural/compressive strength ratios (360-day strength/benchmark strength) of FM0 and FM2 specimens were all larger than 95%. The volume linear expansion rates (S_n) of PMPC specimens continued to increase with the immersion age, and S_n of FM2 specimen was only 49.5% of that of the FM0 specimen at 360-day immersion ages. The results provide an experimental basis for the application of PMPC-based materials. Full article

(This article belongs to the Topic Advanced Composite Materials)

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18 pages, 5716 KB

Open AccessArticle

Influence of Coupled Activated Recycled Fine Powder on the Performance of Ultra-High-Performance Concrete

by Chun Lu, Ming Zhang, Nirmal Shrestha, Dongdong Yang and Chengxiao Yu

Materials 2026, 19(1), 201; https://doi.org/10.3390/ma19010201 - 5 Jan 2026

Viewed by 251

Abstract

Ultra-High-Performance Concrete (UHPC) is being increasingly utilized in major engineering projects due to its excellent mechanical properties, strong durability, and superior overall performance. Nevertheless, the widespread use of premium cementitious materials leads to high expenses and a substantial environmental impact. In this work, [...] Read more.

Ultra-High-Performance Concrete (UHPC) is being increasingly utilized in major engineering projects due to its excellent mechanical properties, strong durability, and superior overall performance. Nevertheless, the widespread use of premium cementitious materials leads to high expenses and a substantial environmental impact. In this work, crushed recycled paste was calcined at 600 °C for two hours to produce calcined recycled fine powder (RFP) with varying hydration reactivity. UHPC was produced using the RFP in place of some of the cement. Chemical activation was accomplished by adding a composite activator system made up of Ca(OH)₂, Na₂SO₄, Na₂SiO₃·9H₂O, and K₂SO₄ in order to further improve the performance of UHPC. Particle size, viscosity, fluidity, mechanical properties, and hydration products were analyzed to establish the best activator type and dosage, as well as the ideal activation procedure for recycled fine powder. By mass replacement of cementitious materials, when 15.0% of the calcined recycled fine powder was added, the compressive strength of UHPC reached 149.1 MPa, a 23.2% increase over reference UHPC without calcined recycled fine powder. The results show that the calcined recycled fine powder ground for 60 min exhibits the highest activity. More hydrated products were formed in UHPC as a result of the addition of Ca(OH)₂. The compressive strength peaked at 162.2 MPa at an incorporation rate of 1.5%, which is 8.8% higher than UHPC without an activator. Full article

(This article belongs to the Special Issue Innovative Construction Materials for Sustainable and Greener Applications)

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21 pages, 5970 KB

Open AccessArticle

Evaluation of Multiple Influences on the Unconfined Compressive Strength of Fibre-Reinforced Backfill Using a GWO–LGBM Model

by Xin Chen, Yunmin Wang, Shengjun Miao, Shian Zhang, Zhi Yu and Linfeng Du

Materials 2026, 19(1), 200; https://doi.org/10.3390/ma19010200 - 5 Jan 2026

Viewed by 264

Abstract

Fibres can markedly enhance the uniaxial compressive strength (UCS) of cemented paste backfill (CPB). However, previous studies have mainly verified the effectiveness of polypropylene and straw fibres in improving the UCS of CPB experimentally, while systematic multi-factor evaluation remains limited. In this study, [...] Read more.

Fibres can markedly enhance the uniaxial compressive strength (UCS) of cemented paste backfill (CPB). However, previous studies have mainly verified the effectiveness of polypropylene and straw fibres in improving the UCS of CPB experimentally, while systematic multi-factor evaluation remains limited. In this study, laboratory experiments were conducted on polypropylene- and straw fibre-reinforced CPB to construct a reliable dataset. The factors influencing the intensity of uniaxial compressive strength were divided into four aspects (mixture proportions, physical properties of the cement–tailings mixture, chemical characteristics of tailings, and fibre properties), and four intelligent models were developed for effectiveness analysis and UCS prediction. SHapley Additive exPlanations (SHAP) were employed to quantify the contributions of individual features, and the findings were experimentally validated. The GWO–LGBM model outperformed the SVR, ANN, and LGBM models, achieving R² = 0.907, RMSE = 0.78, MAE = 0.515, and MAPE = 0.157 for the training set, and R² = 0.949, RMSE = 0.627, MAE = 0.38, and MAPE = 0.115 for the testing set, respectively. Feature analysis reveals that mixture proportions contribute the most to UCS, followed by the tailings’ physical properties, the fibre properties, and the tailings’ chemical characteristics. This study found that cement content and tailings gradation control CPB structural compactness and fibres enhance bonding between hydration products and tailings aggregates, while the chemical composition of the tailings plays an inert role, functioning mainly as an aggregate. Full article

(This article belongs to the Section Construction and Building Materials)

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23 pages, 11387 KB

Open AccessArticle

Immobilization of Lead and Zinc in Tailings Sand Using a Stabilizer Synthesized from Granite Sawdust for Mine Remediation

by Yanping Shi, Mengjia Liang, Man Xue, Zhi Li, Xianyu Yang, Chuyuan Ma, Longchen Duan and Jihua Cai

Materials 2026, 19(1), 199; https://doi.org/10.3390/ma19010199 - 5 Jan 2026

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Abstract

Improper disposal of granite sawdust from stone processing and heavy metal-containing tailings sand can pose severe threats to the environment and human health. Based on their physicochemical properties, granite sawdust was used to synthesize a zeolite-based stabilizer (GFAS) for immobilizing lead (Pb) and [...] Read more.

Improper disposal of granite sawdust from stone processing and heavy metal-containing tailings sand can pose severe threats to the environment and human health. Based on their physicochemical properties, granite sawdust was used to synthesize a zeolite-based stabilizer (GFAS) for immobilizing lead (Pb) and zinc (Zn) in tailings waste. The stabilizer was prepared through an alkali fusion–hydrothermal method, followed by phosphoric acid modification. Characterization by XRD, SEM-EDS, and BET revealed that GFAS possesses a Na-P1 zeolite structure (Na₆Al₆Si₁₀O₃₂) with a micro-mesoporous texture and a specific surface area of 35.00 m²/g, representing a 10-fold increase over raw sawdust. The cation exchange capacity (CEC) of GFAS reached 57.08 cmol⁺/kg, a 116-fold enhancement. The stabilization mechanism involved synergistic physical adsorption, chemical precipitation (e.g., Pb₃(PO₄)₂, Zn(OH)₂), and ion exchange. This study presents a sustainable “waste-treats-waste” strategy for effectively reducing the mobility of heavy metals in tailings waste, thereby contributing to the remediation of seepage from tailings pond foundations. Full article

(This article belongs to the Special Issue Development and Modification of New or Recycled Materials and Technological Processes Toward Sustainable Development (Second Edition))

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15 pages, 3013 KB

Open AccessArticle

Numerical Simulation and Process Optimization of Sn-0.3Ag-0.7Cu Alloy Casting

by Hao Zhou, Yingwu Wang, Jianghua He, Chengchen Jin, Ayiqujin, Desheng Lei, Hui Fang and Kai Xiong

Materials 2026, 19(1), 198; https://doi.org/10.3390/ma19010198 - 5 Jan 2026

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Abstract

Porosity formation due to solidification shrinkage and inadequate liquid metal feeding during the casting of Sn-0.3Ag-0.7Cu (SAC0307) is a critical issue that impairs quality and subsequent processing. However, the opacity of the casting process often obscures the quantitative relationships between process parameters and [...] Read more.

Porosity formation due to solidification shrinkage and inadequate liquid metal feeding during the casting of Sn-0.3Ag-0.7Cu (SAC0307) is a critical issue that impairs quality and subsequent processing. However, the opacity of the casting process often obscures the quantitative relationships between process parameters and defect formation, creating a significant barrier to science-based optimization. To address this, the present study utilizes finite element method (FEM) analysis to systematically investigate the influence of pouring temperature (PCT, 290–390 °C) and interfacial heat transfer coefficient (HTC, 900–5000 W/(m²·K)) on this phenomenon. The results reveal that PCT exerts a non-monotonic effect on porosity by modulating the solidification mode, which governs the accumulation of dispersed microporosity. In contrast, HTC plays a critical role in determining porosity morphology by controlling both the solidification rate and mode. Consequently, an optimal processing window was identified at 350 °C PCT and 3000 W/(m²·K) HTC, which significantly enhances interdendritic feeding and improves the ingot’s internal soundness. The efficacy of these optimized parameters was experimentally validated through macro- and microstructural characterization. This work not only elucidates the governing mechanisms of solidification quality but also demonstrates the value of numerical simulation for process optimization, offering a reliable scientific basis for the industrial production of high-quality SAC0307 alloys. Full article

(This article belongs to the Topic Numerical Modelling on Metallic Materials, 2nd Edition)

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12 pages, 4985 KB

Open AccessArticle

Characterization of Ti/Cu Dissimilar Metal Butt-Welded by the Cold Welding Process

by Yunyi Xiao, Fei Liu and Nuo Chen

Materials 2026, 19(1), 197; https://doi.org/10.3390/ma19010197 - 5 Jan 2026

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Abstract

Titanium alloys and copper have broad applications in aerospace, defense, and industry, but their dissimilar welding faces challenges from significant physicochemical differences and easy formation of brittle Ti-Cu intermetallic compounds, while existing methods like laser welding or friction stir welding have limitations, such [...] Read more.

Titanium alloys and copper have broad applications in aerospace, defense, and industry, but their dissimilar welding faces challenges from significant physicochemical differences and easy formation of brittle Ti-Cu intermetallic compounds, while existing methods like laser welding or friction stir welding have limitations, such as low strength or inability to weld ultra-thin plates. This study adopted cold welding to join Ti-6.5Al-1Mo-1V-2Zr alloy and 99.90% pure copper. The mechanical properties of the joint were tested, the microstructure and fracture of the weld were observed, and the phase composition of the weld was analyzed. The results show that the weld fusion zone mainly consists of Cu-based solid solution and Cu₃Ti. Low cold welding heat input reduces the Cu₃Ti content, so the joint mechanical properties do not decrease significantly. The tensile strength of the joint reaches 284 MPa, which is 83% of that of copper-based metals, and the elongation rate reaches 6.25%. Diffusion kinetics and solidification thermodynamics analyses confirm that Cu₃Ti intermetallic compounds are preferentially generated in the weld seam. Full article

(This article belongs to the Section Mechanics of Materials)

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14 pages, 1620 KB

Open AccessArticle

Accelerating High-Entropy Alloy Design via Machine Learning: Predicting Yield Strength from Composition

by Seungtae Lee, Seok Su Sohn, Hae-Seok Lee, Donghwan Kim and Yoonmook Kang

Materials 2026, 19(1), 196; https://doi.org/10.3390/ma19010196 - 5 Jan 2026

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Abstract

High-entropy alloys (HEAs) have attracted significant attention due to their exceptional physical, chemical, and mechanical properties. The current development of HEAs primarily depends on time-consuming and costly trial-and-error approaches, which not only hinder the efficient exploration of new compositions but also result in [...] Read more.

High-entropy alloys (HEAs) have attracted significant attention due to their exceptional physical, chemical, and mechanical properties. The current development of HEAs primarily depends on time-consuming and costly trial-and-error approaches, which not only hinder the efficient exploration of new compositions but also result in unnecessary resource and energy consumption, thereby negatively affecting sustainable development and production. To address this challenge, this study introduces a machine learning-based methodology for predicting the yield strengths of various HEA compositions. The model was trained using 181 data points and achieved an R² performance score of 0.85. To further assess its reliability and generalization capability, the model was validated using external data not included in the collected dataset. The validation was performed across four categories: modified Cantor alloys, refractory HEAs, eutectic HEAs, and other HEAs. The predicted yield strength trends were found to align with the actual experimental trends, demonstrating the model’s robust performance across various categories of HEAs. The proposed machine learning approach is expected to facilitate the combinatorial design of HEAs, thereby enabling efficient optimization of compositions and accelerating the development of novel alloys. Moreover, it has the potential to serve as a guideline for sustainable alloy design and environmentally conscious production in future HEA development. Full article

(This article belongs to the Topic AI and Computational Methods for Modelling, Simulations and Optimizing of Advanced Systems: Innovations in Complexity, 2nd Edition)

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18 pages, 6057 KB

Open AccessArticle

Fundamentals of Cubic Phase Synthesis in PbF₂–EuF₃ System

by Sofia Zykova, Kristina Runina, Mariya Mayakova, Maria Berezina, Olga Petrova, Roman Avetisov and Igor Avetissov

Materials 2026, 19(1), 195; https://doi.org/10.3390/ma19010195 - 5 Jan 2026

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Abstract

Fluoride solid solutions exhibit exceptional optical and thermodynamic properties that make them valuable for advanced technological applications, and the PbF₂-EuF₃ system represents a particularly promising quasi-binary system for developing high-performance materials. However, the comprehensive understanding of the thermodynamic conditions governing [...] Read more.

Fluoride solid solutions exhibit exceptional optical and thermodynamic properties that make them valuable for advanced technological applications, and the PbF₂-EuF₃ system represents a particularly promising quasi-binary system for developing high-performance materials. However, the comprehensive understanding of the thermodynamic conditions governing phase equilibria and the precise boundaries of homogeneity regions in this system remains incomplete, limiting the rational design of single-phase materials with desired properties. Therefore, we conducted a comprehensive investigation of the thermodynamic conditions (temperature and composition) controlling the existence of cubic and rhombohedral phases within the homogeneity regions of the PbF₂-EuF₃ system. Solid solution samples were synthesized using both solid-phase synthesis and co-precipitation techniques from aqueous nitrate solutions. Phase equilibria were systematically investigated in two critical regions: the solvus line spanning 0–10 mol% EuF₃ and the ordered rhombohedral R-phase region spanning 35–45 mol% EuF₃. Structural characterization was performed at temperatures below the phase transition temperature in lead fluoride (365 °C) using X-ray phase analysis, optical probing, and Raman scattering. Our investigation successfully demonstrated the possibility of obtaining cubic preparations of high purity across the 0–37 mol% EuF₃ composition range. Additionally, we precisely defined the region of existence of the ordered rhombohedral R-phase within the concentration range of 37–39 to 43–44 mol% EuF₃. These findings provide essential thermodynamic data for the rational design of PbF₂-EuF₃ solid solutions and establish clear compositional boundaries for obtaining desired phase structures in this technologically important fluoride system. Full article

(This article belongs to the Section Optical and Photonic Materials)

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18 pages, 4980 KB

Open AccessArticle

Boosted NH₃ Selective Catalytic Oxidation Activity over V-Pt-Ti Catalysts: Insight into Preparation Method Effects

by Yu Gao, Lipeng Wang, Kun Li and Yongbo Ji

Materials 2026, 19(1), 194; https://doi.org/10.3390/ma19010194 - 5 Jan 2026

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Abstract

In this work, V-Pt-Ti catalysts were synthesized employing impregnation (IP), precipitation (PC), sol-gel (SG), thermal decomposition (TD), and hydrothermal (HD) methods. A systematic study has been carried out to investigate impacts of various preparation methods on the performance of NH₃ selective catalytic [...] Read more.

In this work, V-Pt-Ti catalysts were synthesized employing impregnation (IP), precipitation (PC), sol-gel (SG), thermal decomposition (TD), and hydrothermal (HD) methods. A systematic study has been carried out to investigate impacts of various preparation methods on the performance of NH₃ selective catalytic oxidation (SCO) at temperatures from 150 °C to 450 °C. N₂ adsorption/desorption, XPS, XRD, H₂-TPR, NH₃-TPD, O₂-TPD, SEM, TEM, and in situ DRIFTS were adopted to characterize the physico-chemical property of V-Pt-Ti catalysts. The results suggested that V-Pt-Ti catalysts synthesized by precipitation methods (denoted as VPT-PC) exhibited notably better SCO performance across the 150–450 °C temperature range compared with those produced by impregnation (IP), sol-gel (SG), thermal decomposition (TD), and hydrothermal (HD) methods. The outstanding performance of the VPT-PC catalyst could be ascribed to its larger surface area, higher relative contents of Pt⁰, V⁵⁺, and O_α, more abundant surface acid sites, and better redox property. In situ DRIFTS results suggested that NO₂ species could participate in NH₃ oxidation reaction on the surface of the VPT-PC catalyst, which was beneficial for improving the SCO activity. Full article

(This article belongs to the Section Catalytic Materials)

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18 pages, 3611 KB

Open AccessArticle

Comparative Analysis of Two CO₂ Sequestration Pathways for Magnesium Slag Based on Kinetics and Life Cycle Assessment

by Zhen Lu, Yan Wu, Hongshuo Ding, Chengyuan Zhao, Yunlong Bai and Li Zhang

Materials 2026, 19(1), 193; https://doi.org/10.3390/ma19010193 - 5 Jan 2026

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Abstract

As a metallurgical solid waste rich in active calcium oxide, magnesium slag (MS) is endowed with significant carbon dioxide sequestration potential due to its inherent properties, providing a feasible path for the simultaneous solution of waste residue disposal and carbon dioxide emission reduction. [...] Read more.

As a metallurgical solid waste rich in active calcium oxide, magnesium slag (MS) is endowed with significant carbon dioxide sequestration potential due to its inherent properties, providing a feasible path for the simultaneous solution of waste residue disposal and carbon dioxide emission reduction. However, current research has neither clarified the kinetic mechanism (core theoretical support for carbon dioxide sequestration industrialization) nor systematically evaluated the life cycle environmental impacts of MS’s two carbonation routes (direct or indirect leaching carbonation). To address this, this study explores kinetic laws via the single-factor control variable method, and combines life cycle assessment (LCA) to fill the gap, providing key theoretical support for process optimization and engineering promotion. Kinetic results show indirect carbon dioxide sequestration (ICDS) forms an inert silicon-rich layer (core-shrinkage model, mixed control, 28.4 kJ/mol activation energy), while direct carbon dioxide sequestration (DCDS) involves dual-layer formation and pore blockage (mixed control, 14.0 kJ/mol). The ICDS achieves a higher reaction rate of 89%, compared to 63% for the DCDS. In life cycle assessments, DCDS demonstrates outstanding overall environmental sustainability, particularly excelling in carbon dioxide sequestration and acidification control, while ICDS exhibits significant environmental drawbacks (such as high carbon dioxide emissions and ecological toxicity). However, ICDS possesses advantages such as high feedstock utilization and strong synthesis capabilities for high-value-added products. Through targeted optimization, its environmental indicators can be reduced in the future, making it suitable for specific scenarios like high-end calcium carbonate production and resource utilization of low-grade magnesium slag. Full article

(This article belongs to the Special Issue Sustainable Eco-Friendly Advanced Geopolymers: Leveraging Recycled, Bio-Based, and Industrial Waste Constituents)

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30 pages, 4416 KB

Open AccessReview

Research Progress on Asphalt–Aggregate Adhesion Suffered from a Salt-Enriched Environment

by Yue Liu, Wei Deng, Linwei Peng, Hao Lai, Youjie Zong, Mingfeng Chang and Rui Xiong

Materials 2026, 19(1), 192; https://doi.org/10.3390/ma19010192 - 5 Jan 2026

Viewed by 537

Abstract

Salt permeation erosion is a key factor leading to the deterioration of service performance and shortening the lifespan of asphalt pavement in salt-rich areas. In this environment, the combined action of water and salt accelerates the decline in the asphalt–aggregate interface, leading to [...] Read more.

Salt permeation erosion is a key factor leading to the deterioration of service performance and shortening the lifespan of asphalt pavement in salt-rich areas. In this environment, the combined action of water and salt accelerates the decline in the asphalt–aggregate interface, leading to distress, such as raveling and loosening, which severely limit pavement durability. The authors systematically reviewed the research progress on asphalt–aggregate adhesion in a saline corrosion environment and discussed the complex mechanisms of adhesion degradation driven by intrinsic factors, including aggregate chemical properties, surface morphology, asphalt components, and polarity, as well as environmental factors, such as moisture, salt, and temperature. We also summarized multi-scale evaluation methods, including conventional macroscopic tests and molecular dynamics simulations, and revealed the damage evolution patterns caused by the coupled effects of water, salt, heat, and mechanical forces. Based on this, the effectiveness of technical approaches, such as asphalt modification and aggregate modification, is explored. Addressing the current insufficiency in research on asphalt adhesion under complex conditions in salt-rich areas, this study highlights the necessity for further research on mechanisms of multi-environment interactions, composite salt erosion simulation, development of novel anti-salt erosion materials, and intelligent monitoring and early warning, aiming to provide a theoretical basis and technical support for the weather-resistant design and long-term service of asphalt pavement in salt-rich regions. Full article

(This article belongs to the Special Issue Innovations in Sustainable Construction and Road Engineering Materials)

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26 pages, 4117 KB

Open AccessArticle

Analysis of Physical Processes in Confined Pores of Activated Carbons with Uniform Porosity

by Magdalena Blachnio, Malgorzata Zienkiewicz-Strzalka and Anna Derylo-Marczewska

Materials 2026, 19(1), 191; https://doi.org/10.3390/ma19010191 - 4 Jan 2026

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Abstract

Mesoporous carbons based on silica hard templates were used to investigate physical processes in confined pores. Nitrogen adsorption, scanning electron microscopy, and scattered X-ray analyses revealed two classes of materials: carbons with moderate and highly developed mesoporosity. The pore structure was strongly dependent [...] Read more.

Mesoporous carbons based on silica hard templates were used to investigate physical processes in confined pores. Nitrogen adsorption, scanning electron microscopy, and scattered X-ray analyses revealed two classes of materials: carbons with moderate and highly developed mesoporosity. The pore structure was strongly dependent on pore expanders which proved essential for generating open, accessible architectures. All carbons exhibited a basic, graphitic surface (pH_PZC = 8.4–10.9), enriched in electron-donating oxygen functionalities. Differential scanning calorimetry studies of confined water showed that melting point depression follows the Gibbs–Thomson relationship, confirming the strong dependence of phase transitions on pore size and water–surface interactions. Adsorption experiments using methylene blue demonstrated that capacity is governed by surface area, pore volume, and pore size distribution. For carbon with the largest average pore size, adsorption of various dyes revealed that uptake decreases with increasing molecular size, whereas affinity depends strongly on electrostatic interactions. Kinetic studies indicated that carbons with larger mesopores exhibit the fastest adsorption, and that large, complex dye molecules undergo significant diffusion limitations. Overall, the results show that the interplay between pore structure, adsorbate size, and surface chemistry influences both the equilibrium uptake and adsorption kinetics in mesoporous carbon materials. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials: Simulation, Design, Synthesis, Properties, Applications)

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18 pages, 4166 KB

Open AccessFeature PaperArticle

The Effects of Cr and Mo Additions on the Corrosion Behavior of Fe–Al Alloys in 0.5 M H₂SO₄ and 3.5 wt.% NaCl Aerated Aqueous Solutions

by Chao-Chun Yen, Ting-Hsu Chang, Yun-Xian Lin, Meng-Ying Wu and Shiow-Kang Yen

Materials 2026, 19(1), 190; https://doi.org/10.3390/ma19010190 - 4 Jan 2026

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Abstract

This study aims to investigate the effects of Cr and Mo added to Fe-Al alloys on their corrosion behavior in acidic and chloride-containing environments. Corrosion tests were carried out in 0.5 M H₂SO₄ and 3.5 wt.% NaCl aerated aqueous solutions. [...] Read more.

This study aims to investigate the effects of Cr and Mo added to Fe-Al alloys on their corrosion behavior in acidic and chloride-containing environments. Corrosion tests were carried out in 0.5 M H₂SO₄ and 3.5 wt.% NaCl aerated aqueous solutions. X-ray diffraction analyses reveal that all alloys exhibited predominantly body-centered cubic structures in the homogenized states. In the 0.5 M H₂SO₄ solution, the addition of Cr can effectively reduce the critical current density; however, the anodic and cathodic polarization curves still intersected three times, similar to the alloy without the addition of Cr, resulting in three corrosion potentials. With the further addition of Mo, the critical current density became much lower, leading to a single corrosion potential. In the 3.5 wt.% NaCl solution, the addition of Cr alone markedly improved the pitting resistance of Fe-Al alloys, while the further addition of Mo broadened the passive region and increased the pitting potential. The analysis of ion concentrations was consistent with the potentiodynamic polarization results, verifying the stabilization of Mo on the passive film. It is evident that the addition of Cr promotes passivation of the Fe-Al alloy, and the further incorporation of Mo enhances this effect even more significantly. The related corrosion mechanisms are discussed with Nerst equations of metal–metal oxides and their solubility products (K_sp). Full article

(This article belongs to the Special Issue Next-Generation Alloys: Nanostructured Metals, Complex Steels, and Multi-Component Systems)

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31 pages, 6698 KB

Open AccessArticle

Investigation of Ensemble Machine Learning Models for Estimating the Ultimate Strain of FRP-Confined Concrete Columns

by Quang Trung Nguyen, Anh Duc Pham, Quynh Chau Truong, Cong Luyen Nguyen, Ngoc Son Truong and Anh Duc Mai

Materials 2026, 19(1), 189; https://doi.org/10.3390/ma19010189 - 4 Jan 2026

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Abstract

Accurately predicting the ultimate strain of fiber-reinforced polymer (FRP)-confined concrete columns is essential for the widespread application of FRP in strengthening reinforced concrete (RC) columns. This study comprehensively investigates the performance of ensemble machine learning (ML) models in estimating the ultimate strain of [...] Read more.

Accurately predicting the ultimate strain of fiber-reinforced polymer (FRP)-confined concrete columns is essential for the widespread application of FRP in strengthening reinforced concrete (RC) columns. This study comprehensively investigates the performance of ensemble machine learning (ML) models in estimating the ultimate strain of FRP-confined concrete (FRP-CC) columns. A dataset of 547 test results of the ultimate strain of FRP-CC columns was collected from the literature for training and testing ML models. The four best single ML models were used to develop ensemble models employing voting, stacking and bagging techniques. The performance of the ensemble models was compared with 10 single ML and 11 empirical strain models. The study results revealed that the single ML models yielded good agreement between the estimated ultimate strain and the test results, with the best single ML models being the K-Star, k-Nearest Neighbor (k-NN) and Decision Table (DT) models. The three best ensemble models, a stacking-based ensemble model comprising K-Star, k-NN and DT models; a stacking-based ensemble model comprising K-Star and k-NN models and a voting-based ensemble model comprising K-Star and k-NN models, achieved higher estimation accuracy than the best single ML model in estimating the strain capacity of FRP-CC columns. Full article

(This article belongs to the Section Construction and Building Materials)

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17 pages, 5059 KB

Open AccessArticle

Assessment of the Possibilities of Developing Effective Building Thermal Insulation Materials from Corrugated Textile Sheets

by Sigitas Vėjelis, Aliona Drozd, Virgilijus Skulskis and Saulius Vaitkus

Materials 2026, 19(1), 188; https://doi.org/10.3390/ma19010188 - 4 Jan 2026

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Abstract

Low-density thermal insulation materials tend to settle during operation or under small loads. Resistance to loads and settling is ensured by increasing the density of thermal insulation materials several times. This increases the weight of the material and the structure and production costs. [...] Read more.

Low-density thermal insulation materials tend to settle during operation or under small loads. Resistance to loads and settling is ensured by increasing the density of thermal insulation materials several times. This increases the weight of the material and the structure and production costs. In this work, using various technological processes, corrugated textile sheets and thermal insulation materials were produced from textile fabric. The development of such materials as effective thermal insulation materials for building insulation has not yet been studied. The corrugation of textile sheets enabled the thermal insulation material to exhibit good mechanical and deformation properties without increasing its density or thermal conductivity. The density of the specimens of the thermal insulation material made from corrugated sheets ranged from 76.8 to 51.9 kg/m³, and the thermal conductivity ranged from 0.0535 to 0.0385 W/(m·K). The most significant influences on density and thermal conductivity were the wave size and the adhesive layer. The density of unglued sheets of the same composition ranged from 51.3 to 29.8 kg/m³, and the thermal conductivity ranged from 0.0530 to 0.0371 W/(m·K). The highest compressive and bending strengths were observed in thermal insulation materials prepared from finely corrugated sheets. Their compressive stress at 10% deformation was 17.3 kPa, and their bending strength was −157 kPa. In comparison, the compressive stress of thermal insulation materials of the same density as non-corrugated sheets was only 0.686 kPa and, in the case of bending strength, 9.90 kPa. The obtained results show that the application of materials engineering principles allows us to improve the performance characteristics of materials. Full article

(This article belongs to the Special Issue New Thermal Insulation Materials in Green Buildings)

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5 pages, 163 KB

Open AccessEditorial

Current Status and Trends of the Cement Admixtures

by Hongwei Wang and Ying Shi

Materials 2026, 19(1), 187; https://doi.org/10.3390/ma19010187 - 4 Jan 2026

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Abstract

Cement-based materials are central to modern infrastructure construction [...] Full article

(This article belongs to the Special Issue Effects of Adding Cement Admixtures on the Microstructure and Properties of Cement Materials)

18 pages, 10634 KB

Open AccessArticle

Effect of Nano-TiO₂ Addition on Some Properties of Pre-Alloyed CoCrMo Fabricated via Powder Technology

by Jawdat Ali Yagoob, Mahmood Shihab Wahhab, Sherwan Mohammed Najm, Mihaela Oleksik, Tomasz Trzepieciński and Salwa O. Mohammed

Materials 2026, 19(1), 186; https://doi.org/10.3390/ma19010186 - 4 Jan 2026

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Abstract

The CoCrMo alloys are progressively utilized as biomaterials. This research is dedicated to studying the consequence of (1, 3, and 5) wt% nano-TiO₂ addition on the porosity, microstructure, microhardness, and wear behavior of pre-alloyed CoCrMo powder produced by powder metallurgy (PM). Microstructural [...] Read more.

The CoCrMo alloys are progressively utilized as biomaterials. This research is dedicated to studying the consequence of (1, 3, and 5) wt% nano-TiO₂ addition on the porosity, microstructure, microhardness, and wear behavior of pre-alloyed CoCrMo powder produced by powder metallurgy (PM). Microstructural features were examined using SEM, SEM mapping, and XRD. Wear behavior was assessed through pin-on-disk tests performed under dry sliding conditions at varying loads and durations. Porosity increased with the addition of nano-TiO₂, from 15.26 at 0 wt% reaching 25.12% at 5 wt%, while density decreased from 7.16 to 6.33 g/cm³. Microhardness exhibited a slight improvement, attaining 348 HV at 5 wt%. SEM and XRD analyses confirmed partial particle separation after sintering and identified the TiO₂ reinforcement as rutile. Wear tests revealed that adding 1 wt% nano-TiO₂ enhanced wear resistance, whereas extended sliding durations resulted in increased wear rates. Adhesive wear was the predominant mechanism, accompanied by limited abrasive wear, oxidation, and plastic deformation. Full article

(This article belongs to the Section Biomaterials)

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25 pages, 1939 KB

Open AccessArticle

Application of Potato Peels as an Unconventional Sorbent for the Removal of Anionic and Cationic Dyes from Aqueous Solutions

by Tomasz Jóźwiak, Urszula Filipkowska, Anna Nowicka and Jarosław Kaźmierczak

Materials 2026, 19(1), 185; https://doi.org/10.3390/ma19010185 - 4 Jan 2026

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Abstract

The aim of this study was to investigate the sorption efficiency of anionic dyes—Reactive Yellow 84 (RY84) and Reactive Black 5 (RB5)—and cationic dyes—Red 46 (BR46) and Basic Violet 10 (BV10)—onto potato peels (Solanum tuberosum L.). The research scope included characterization of [...] Read more.

The aim of this study was to investigate the sorption efficiency of anionic dyes—Reactive Yellow 84 (RY84) and Reactive Black 5 (RB5)—and cationic dyes—Red 46 (BR46) and Basic Violet 10 (BV10)—onto potato peels (Solanum tuberosum L.). The research scope included characterization of the sorbent material (pH_PZC, FTIR), the effect of pH on dye sorption efficiency, kinetics (pseudo-first-order and pseudo-second-order models, intraparticle diffusion model), and studies on the sorbent’s maximum sorption capacity (Langmuir 1 and 2, and Freundlich isotherms). The point of zero charge (pH_PZC) for potato peels was determined to be pH_PZC = 6.43, indicating a slightly acidic character of the material. The sorption efficiency for RB5, RY84, and BV10 was highest at pH 2, while the efficiency for BR46 was highest at pH 6. The time required to reach sorption equilibrium on the tested sorbent increased with the initial dye concentration and ranged from 180 to 270 min for RB5, RY84, and BV10, and from 45 to 210 min for BR46. The maximum sorption capacity of this material was found to be 20.85 ± 0.33 mg/g and 21.63 ± 0.34 mg/g for RB5 and RY84, respectively, and 10.28 ± 0.24 mg/g and 27.15 ± 0.87 mg/g for BV10 and BR46, respectively. Full article

(This article belongs to the Special Issue Advanced Technologies and Materials for Wastewater Treatment)

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