Search Results (82)

Moisture-induced damage is one of the primary causes of premature distress in asphalt pavements, leading to reduced service life and increased maintenance costs. Although nanomaterials have shown potential in enhancing asphalt performance, the underlying composite interaction mechanisms among nanomaterials, asphalt binder, and aggregate phases under moisture exposure are still not fully understood. In addition, comparative evaluations under consistent experimental conditions remain limited. This study investigates the influence of five nanomaterials: nano-silica (NS), nano-alumina (NA), nano-titanium dioxide (NT), nano-zinc oxide (NZ), and carbon nanotubes (CNT) on the physical and mechanical properties of asphalt binders and mixtures, with particular emphasis on moisture damage resistance. The nanomaterials were incorporated at dosages of 1.5%, 3.0%, 4.5%, and 6.0% by binder weight. Binder performance was evaluated using conventional and performance grading (PG) tests, while mixture performance was assessed through Marshall properties and moisture susceptibility indicators, including the tensile strength ratio (TSR) and the index of retained strength (IRS). Fluorescence microscopy (FM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were employed to investigate nanomaterial dispersion characteristics, microstructural morphology, and physicochemical interactions within the asphalt composite system. The results indicate that nanomaterial modification reduced penetration and increased softening point and Marshall stability, reflecting enhanced stiffness and thermal resistance, although ductility decreased at higher dosages. Significant improvements in moisture resistance were observed, particularly under conditioned states. The TSR increased from 81.2% for the control mixture to 92.4% for NS and 91.7% for NA, while the IRS improved from 72.7% to 88.5% for NS. Statistical analysis indicated that both nanomaterial type and dosage significantly affected TSR and IRS performance, with dosage exhibiting comparatively greater influence on moisture resistance improvement. FM and SEM analyses revealed comparatively better dispersion and lower agglomeration tendency for NS and NA, which corresponded to their superior moisture resistance performance. FTIR analysis indicated that the modification process was predominantly physical, with no major formation of new chemical functional groups. Among the investigated nano materials, NS at 6% dosage exhibited the most pronounced improvement, followed by NA at similar dosage levels. Overall, the findings suggest that nanomaterial modification can considerably improve the moisture resistance and mechanical performance of asphalt mixtures under laboratory conditions. However, higher nanomaterial dosages may adversely affect binder workability due to increased viscosity, particularly in CNT-modified binders. Full article

Nanoparticle-modified concrete can exhibit improved mechanical performance, yet its residual compressive strength (Fc) after fire-like thermal exposure is difficult to predict because the response depends on both mixture design and heating conditions. Building on recent advances in explainable machine learning (ML) for cementitious materials, this study compiles 218 literature datapoints of post-heating Fc from 100 mm concrete cubes incorporating carbon nanotubes (CNTs) and nano-alumina (NA), exposed to 20–800 °C for up to 2 h. Seven input variables are used: cement-to-total aggregate ratio, CNT-to-cement ratio, NA-to-cement ratio, coarse-to-fine aggregate ratio, water-to-cement ratio, peak temperature, and exposure duration at temperature. Two particle-swarm-optimized ensemble regression models, Extreme Gradient Boosting (XGB-PSO) and Random Forest (RF-PSO), were developed and evaluated using a 70/30 train–test split with K-fold cross-validation on the training set. SHAP, individual conditional expectation (ICE), and partial dependence plots (PDPs) were employed to study the individual and combined effects of each input parameter on Fc prediction. The results demonstrated that the XGB-PSO model provides the best predictive performance (training R² = 0.9983; testing R² = 0.9434; testing MAE = 1.3168 MPa). Model interpretability was assessed using SHAP, ICE, and PDP analyses, revealing that temperature and exposure duration dominate strength loss, while CNTs and NA contribute positively within dose-dependent regimes. The highest predicted strengths occur for CNTs of 0.05% to 0.15% and NA of 0.65 to 2.71% (by cement mass) under moderate temperature exposure. A Python-based graphical user interface is provided to support rapid what-if assessment of CNT–NA mixtures under elevated-temperature scenarios. Full article

The rational design of supported Lewis acid catalysts is frequently impeded by an incomplete understanding of how the support’s synthetic history governs its intrinsic acidity and catalytic efficacy. Herein, we elucidate the structure–property–performance relationship linking the aging dynamics of a boehmite precursor to the activity of the resultant chlorinated alumina (Al₂O₃–Cl) catalyst in n-butane isomerization. Using n-butane as the probe feedstock, we investigated how alumina supports with distinct physicochemical properties regulate the performance of Al₂O₃–Cl catalysts for n-butane isomerization. By systematically adjusting the aging parameters (stirring rate, temperature, and time), we reveal that the structural evolution of the alumina support transitions from initial particle aggregation to Ostwald ripening and surface reconstruction. A decisive structure–performance correlation is identified: precursor synthesis conditions govern both the population and accessibility of specific surface hydroxyls (notably Type II terminal OH groups), which act as anchoring sites for the generation of active Lewis acid centers upon chlorination. Optimal aging parameters (300 rpm, 90 °C, 6 h) promote the formation of a hierarchical pore architecture with a maximized density of accessible hydroxyls, thereby affording enhanced Lewis acidity and superior isomerization activity. This work provides a fundamental framework for tailoring solid acid catalysts by precisely engineering the precursor architecture. Full article

The incorporation of recycled metallurgical slags into refractory materials constitutes a promising approach to enhancing sustainability in the refractory industry. This study investigates the effect of vanadium-bearing slag aggregates as partial replacements for tabular alumina in castables and compares their behaviour with high-alumina and bauxite-based castables. Two vanadium-bearing slags with different mineralogical compositions were introduced in the 1–3 mm aggregate fraction with substitution up to 25 wt.%. Their effects on microstructure, thermo-mechanical performance, and corrosion resistance were evaluated. The introduction of vanadium-bearing slag significantly alters the microstructure of the castables, affecting their performance. Both slags displayed grains with higher porosity, microcracking, and heterogeneity compared with tabular alumina, but showed similarities to bauxite grains. Slag 1, enriched in calcium aluminate phases, provides limited mechanical strength but improved corrosion resistance due to improved bonding with the matrix. Slag 2, containing a higher spinel content, enhances mechanical strength, showing behaviour comparable with bauxite-based castables, particularly at 10 wt.% replacement. Vanadium is mainly present in metallic form and as Mg(Al,V)₂O₄ spinels in both slags. Upon firing, vanadium migrates toward the grain boundaries and reacts with the surrounding calcium aluminate phases to be incorporated in Ca(Al,V)₂O₄ and Ca(Al,V)₄O₇, while the spinel phase remains stable. Full article

How would it be possible to functionalize ceramic aggregates for use in refractories? In this work, we demonstrate how paste extrusion can be used to fabricate layered and porous Nb-Al₂O₃-based composite refractories for adjusting thermal and electrical conductivity. Additive manufacturing is used to generate a specific sequence of alumina and composite layers. After drying, the samples were sintered at 1600 °C, crushed, and sieved into particle sizes up to 3150 µm. The rheology of the paste revealed the intended shear-thinning behavior with microcrack formation between the yield and flow strain. The sintered material showed promising thermal-shock characteristics reaching plateau values after the third cycle without signs of further structural damage up to the fifth thermal shock. The layered microstructure was retained after crushing the composites, establishing functionalization of the refractory granules for all particle sizes. Full article

The performance of cement adhesive in large-tonnage insulators is crucial for determining their structural stability and service life when subjected to long-term electromechanical loading and complex environmental interactions. This work addresses the issue of late-stage strength reduction in alumina cement by employing a rapid steam curing process. The influence of curing temperature on the phase composition and microstructure of the hydration products is investigated, along with the evolution over time of the mechanical properties, dry shrinkage rate and elastic modulus. These findings are further validated through thermal–mechanical performance testing of bonded insulators. The results demonstrate that: (1) The hydration products of the adhesive are significantly influenced by steam curing temperature: the metastable phase CAH₁₀ forms at 20 °C; it transforms into the metastable phase C₂AH₈ at 50–60 °C; it changes to the stable phase C₃AH₆ at 70 °C; and microcracks appear and porosity increases at 80–90 °C, although the stable phase C₃AH₆ remains the dominant phase. (2) Alumina cement adhesive prepared via 2 h steam curing at 70 °C exhibited superior properties, with flexural and compressive strengths reaching 14.2 MPa and 112.7 MPa, respectively. After 360 days, flexural strength remained above 12 MPa and compressive strength exceeded 110 MPa. Dry shrinkage was below 0.04%, with an elastic modulus of approximately 49.6 GPa. (3) Microstructural analysis revealed that the hydration products of the cured adhesive were predominantly C₃AH₆ and AH₃, exhibiting stable structures. After 90 days, porosity decreased to 3.56%, with the C₃AH₆ and AH₃ gels tightly enveloping the aggregates and forming a dense, three-dimensional network structure. (4) All bonded insulators successfully passed thermomechanical performance tests. Therefore, this work can provide a good way to prepare a high-performance cement adhesive for insulators. Full article

Photo-Fenton advanced oxidation processes are promising and sustainable approaches for water treatment, particularly under visible-light irradiation. In this study, Cu-Fe bimetallic catalysts supported on silica and γ-alumina were developed for visible-light-driven photo-Fenton reactions, with emphasis on the influence of metal ratios and support-metal interactions on charge–carrier dynamics and hydroxyl radical formation. Comprehensive characterization (XRD, TEM, UV-Vis DRS, PL, TCSPC, and EPR) revealed stronger metal–support interactions and higher metal dispersion on γ-alumina, while silica-supported catalysts showed CuO aggregation at higher Cu loadings. Catalytic performance was evaluated using coumarin oxidation as both a model reaction and a quantitative probe for ^•OH radical generation. Alumina-supported catalysts exhibited superior activity, and ^•OH production increased with increasing Cu content on both supports. Importantly, iron was found to play a dual role: low Fe loading enhances photo-Fenton activity, whereas higher Fe content promotes charge–carrier recombination, leading to reduced activity under visible-light irradiation. These results highlight how the interplay between Fe/Cu ratio and support material governs charge dynamics and provides clear guidelines for the rational design of efficient heterogeneous photo-Fenton catalysts. Full article

Micron-sized near-spherical α-Al₂O₃ powders are widely used as thermal fillers due to their high thermal conductivity, high packing density, good flowability, and low cost. During the high-temperature calcination, the resulting α-Al₂O₃ powders often exhibit an aggregated worm-like morphology owing to limitations in solid-state mass transfer. Researchers have employed various mineralizers to regulate the morphology of α-Al₂O₃ powders; however, the preparation of micron-sized highly spherical α-Al₂O₃ powders via solid-state calcination is still a great challenge. In this work, micron-sized near-spherical α-Al₂O₃ powders were synthesized through high-temperature calcination using hydratable alumina (ρ-Al₂O₃) as precursor with water-soluble mineralizer ammonium fluoroborate (NH₄BF₄). ρ-Al₂O₃ can undergo a hydration reaction with water to form AlO(OH) and Al(OH)₃ intermediates, serving as an excellent precursor. With the addition of 0.1 wt% NH₄BF₄, the product exhibits an optimal near-spherical morphology. Excessive addition (>0.2 wt%), however, significantly promotes the transformation of α-Al₂O₃ from a near-spherical to a plate-like structure. Further studies reveal that the introduction of NH₄BF₄ not only modulates the crystal morphology but also effectively reduces the content of sodium impurities in the powder through a high-temperature volatilization mechanism, thereby enhancing the thermal conductivity of the powder. It is shown that the thermal conductivity of the micron-sized α-Al₂O₃/ epoxy resin composites reaches 1.329 ± 0.009 W/(m·K), which is 7.4 times that of pure epoxy resin. Full article

In this study, we investigate the phase transition process during high-alumina, low-lithium glass-ceramics (ZnO-MgO-Li₂O-SiO₂-Al₂O₃) crystallization. The differential scanning calorimetry and high-temperature X-ray diffraction results show that approximately 10 wt.% of (Zn, Mg)Al₂O₄ crystals precipitated when the heat treatment temperature reached 850 °C, indicating that a large number of nuclei had already formed during the earlier stages of heat treatment. Field emission transmission electron microscopy used to observe the microstructure of glass-ceramics after staged heat treatment revealed that cation migration occurred during the nucleation process. Zn and Mg aggregated around Al to form (Zn, Mg)Al₂O₄ nuclei, which provided sites for crystal growth. Moreover, high-valence Zr aggregated outside the glass network, leading to the formation of nanocrystals. Raman spectroscopy analysis of samples at different stages of crystallization revealed that during spinel precipitation, the Q³ and Q⁴ structural units in the glass network increased significantly, along with an increase in the number of bridging oxygens. Highly coordinated Al originally present in the network mainly participated in spinel nucleation, effectively suppressing the subsequent formation of Li_xAl_xSi_1−xO₂, which eventually resulted in the successful preparation of glass-ceramics with (Zn, Mg)Al₂O₄ and ZrO₂ as the main crystalline phases. The grains in this glass-ceramic are all nanocrystals. Its Vickers hardness and flexural strength can reach up to 875 Hv and 350 MPa, respectively, while the visible light transmittance of the glass-ceramic reaches 81.5%. This material shows potential for applications in touchscreen protection, aircraft and high-speed train windshields, and related fields. Full article

River sediments have attracted increasing attention as alternative raw materials for sustainable cementitious materials due to their abundant availability and silica–alumina-rich composition. In this study, a systematic literature search was conducted in Web of Science and Google Scholar using combinations of the keywords “river sediment,” “cementitious materials,” “activation,” and “pozzolanic activity,” covering publications up to July 2025. In addition, a citation network tool (Connected Papers) was employed to trace related works and ensure comprehensive coverage of emerging studies. This review systematically examines the properties of river sediments from diverse regions, along with activation and modification techniques such as alkali/acid activation, thermal calcination, and mechanical milling. Their applications in various cementitious systems are analyzed, with mix design models compared to elucidate the effects of replacing fine aggregates, coarse aggregates, and cement on workability, strength, and durability. Multi-scale characterization via XRD, FTIR, and TG-DSC reveals the mechanisms of C–S–H and C–A–S–H gel formation, pore refinement, and interfacial transition zone densification. The review highlights three key findings: (1) moderate sediment replacement (20–30%) improves strength without compromising flowability; (2) alkali–water glass activation and calcination at 600–850 °C effectively enhance pozzolanic activity; and (3) combining the minimum paste thickness theory with additives such as water reducers, fibers, or biochar enables high-performance and low-carbon concrete design. This review provides a comprehensive theoretical foundation and technical pathway for the high-value utilization of river sediments, carbon reduction in concrete, and sustainable resource recycling. Full article

A large number of wind turbine blades will be retired in the near future. Glass fiber-reinforced composites from retired blades, due to their extraordinary strength, toughness, and durability, are promising aggregate candidates in asphalt mixtures. This work studied the interfacial behavior between asphalt and glass fiber-reinforced composites through combined molecular modeling and experimental approaches. Predictions from molecular modeling were first verified through experimental findings using particle probe scanning force microscopy. Then, molecular simulations were conducted to examine the chemical adhesion between binders and aggregates made from minerals and wind turbine blades. The results showed that epoxy–binder adhesion was higher than calcite–binder and silica–binder adhesion but lower than alumina–binder adhesion, denoting that the glass fiber composite aggregates were comparable in chemical adhesion to mineral aggregates. The adhesion was primarily due to van der Waals forces (>80%). Furthermore, the dependence of epoxy–asphalt adhesion on loading rates was examined, during which the high-speed, transitions, and low-speed regions were identified. The impact of water on interfacial behavior was illustrated by examining how water molecules infiltrated interfaces between aggregates and binders at different speeds. The results showed that interfacial adhesion in a hydrated state at low speeds was 20–40% lower than that in a dry state, whereas at high speeds, interfacial adhesion in a hydrated state was 5–15% higher than that in dry conditions. These results could provide essential guidance for the application of retired wind turbine blades as asphalt aggregates. Full article

The Qinghai–Tibet Plateau presents a unique challenge for infrastructure development due to its extreme geological and climatic conditions—high elevation, large diurnal temperature fluctuations, frequent freeze–thaw cycles, intense ultraviolet radiation, and seasonal precipitation. These factors greatly accelerate the weathering of rock materials, leading to aggregates with increased porosity, microcracking, and weakened mechanical properties. While the engineering implications of such degradation are evident, the underlying material science of weathered aggregates—particularly their microstructure–property relationships—remains insufficiently explored, necessitating further investigation to inform material selection and design. In this study, three representative types of weathered aggregates (silica-rich, carbonaceous, and alumina-rich), alongside unweathered natural aggregates, were examined through both macro-scale (density, water absorption, crushing value, abrasion resistance) and micro-scale (scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS)) analyses. To capture the material evolution, we introduced a simplified classification framework based on the Si/Al ratio and porosity and applied a gray entropy correlation model to quantify the coupling between microstructure and mechanical performance. Results show that weathering reduces the Si/Al ratio from 2.45 to 1.82, increases porosity from 4.2% to 12.7%, enlarges the average pore size to 0.85 μm, raises microcrack density to 1.40 μm/μm², and increases the proportion of connected pores to 68.2%. These microstructural degradations correlate with decreased aggregate density, increased water absorption (up to 8.0%), higher crushing value (27.4%), and abrasion resistance loss (26.0%). Based on these findings, a weathered aggregate classification and pretreatment strategy is proposed, offering a practical reference for engineers to improve material performance in high-altitude road construction. Full article

Porous ceramics have been widely used in various fields. In this paper, porous ceramics with through-hole structures were prepared using a novel and eco-friendly gel casting method with carrageenan as the gelling agent. Especially, the idea of large size particle stacking is introduced into the gel casting process. By introducing large size alumina aggregates as raw materials, and small size micropowders as filling materials, micropores were directly formed after the green body was sintered. To tune the pore size, pore structure, gas permeability, the strength of the final porous ceramics, the components of the raw materials including the alumina aggregates, the filling materials, and sintering additives in the slurry were precisely designed. Porous Al₂O₃-based ceramics with high gas permeability, high flexural strength, and moderate porosity were finally obtained. Full article

One of the effective types of heat-resistant insulating products with an operating temperature of 1050 °C is made from calcium silicates or their hydrates. These materials are made from synthetic xonotlite and 1.13 nm tobermorite. Various wastes and by-products from other industries can be used for the synthesis of the latter compound. However, such raw materials often contain various impurities, especially Al-containing compounds, which strongly influence the kinetics of 1.13 nm tobermorite formation and its properties. Using XRD, DSC, TG, and SEM/EDX methods, it was found that at the beginning of the hydrothermal synthesis, the Al₂O₃ additive promotes the formation of 1.13 nm tobermorite; however, it later begins to inhibit the recrystallization of semi-crystalline C-S-H(I)-type calcium silicate hydrate and pure, high-crystallinity 1.13 nm tobermorite is more easily formed in mixtures without the aluminum additive. Aluminum oxide also influence the morphology of 1.13 nm tobermorite. When hydrothermally curing the CaO–SiO₂ mixture, long, thin fibers (needles) are formed within 24 h. Later, they thicken and form rectangular parallelepiped crystals. After adding alumina, the product produced by 24 h synthesis is dominated by agglomerates, the surface of which is partially covered with crystal plates. By extending the synthesis duration, amorphous aggregates are absent and the crystal shape becomes increasingly square. Full article

Porous artificial reef materials made of cement used in the offshore area can repair and improve the ecological environment and enrich fishery resources. In this study, quartz sand was used as the aggregate, high-alumina cement as the cementing agent, and crushed particles of waste tires as the modifier to prepare porous cement–polymer composites. Through orthogonal tests, the effects of the aggregate particle size, the ratio of aggregate to cement, the rubber particle size, and the rubber ratio on the strength and permeability of the porous cement–polymer composites were studied. The significant degrees of different influencing factors were analyzed, and an appropriate configuration scheme for the porous cement–polymer composites was proposed. The experimental results show that the quantity of rubber particles added and the particle size of the rubber particles have a relatively large impact on the properties of the porous cement–polymer composites. Through response surface tests, the interactive effects of various factors in the porous cement–polymer composites on the compressive strength and permeability of the material were verified. The microstructure of the porous cement–polymer composites was observed by SEM. The differences in the microstructure and internal structure between the specimens with a low rubber content and large rubber particle size and those with a high rubber content and small rubber particle size were analyzed, and the influence mechanism of the differences in the microstructure and internal structure on the strength and permeability was proposed. Full article