Search Results (282)

Ambient-curing epoxy–urethane reactive polymer composites require a balance between initial flowability and subsequent structure buildup. In this study, epoxy–urethane reactive polymer composites containing precipitated calcium carbonate were prepared and referred to as EUPC formulations. Their rheological evolution was characterized by flow sweep, temperature sweep, time sweep, three-interval thixotropy tests (3ITT), amplitude sweep, and oscillatory time sweep. The formulations exhibited distinct initial flow resistance and strong temperature sensitivity, with apparent viscosity decreasing as temperature increased. During ambient curing, viscosity increased continuously, indicating progressive rheological buildup under the selected testing conditions. The 3ITT results showed high-shear-induced apparent viscosity reduction followed by recovery-stage viscosity evolution after returning to the low-shear condition, indicating that the recovery index should be interpreted as an apparent post-shear recovery index rather than a purely thixotropic recovery parameter. Oscillatory measurements revealed a gradual transition from viscous-dominated to more elastic-dominated behavior, and the apparent gel time followed the sequence EUPC-2 < EUPC-4 < EUPC-1 < EUPC-3 < EUPC-5 < EUPC-6. These results indicate that EUPC processability and structure buildup should be evaluated by integrating initial viscosity, temperature sensitivity, post-shear response, and operational viscous-to-elastic transition. Full article

Natural lacquer, a bio-based polymer derived from Toxicodendron vernicifluum, has attracted renewed scientific interest as a sustainable coating material with exceptional mechanical durability, chemical resistance, and aesthetic qualities. This review synthesizes current knowledge on the chemical composition, enzymatic curing mechanisms, and structure–property relationships of lacquer-based polymer systems, with particular focus on recent advances in functional modification and processing technology. Key findings indicate that laccase-catalyzed oxidative polymerization, operating optimally at pH 6.0–7.5 and 20–30 °C, governs the formation of a highly cross-linked urushiol network whose properties are fundamentally determined by side-chain unsaturation and emulsion stability. Mechanistic analysis reveals that polyurethane hybridization improves weathering resistance by introducing flexible aliphatic segments and additional hydrogen-bonding cross-links, while graphene oxide incorporation enhances anticorrosion performance through a physical barrier mechanism that prolongs ionic diffusion pathways. UV-curable LPEA derivatives achieve an 83% reduction in curing time relative to ambient-cured lacquer, enabling integration with industrial spray-coating lines. Despite these advances, several critical limitations remain inadequately resolved. Allergen reduction strategies have not yet achieved sufficient quantitative efficiency for large-scale commercial deployment, and the long-term stability of nanocomposite lacquer films under sustained UV exposure and hydrothermal conditions is not well established. Furthermore, most high-performance modification systems reported in the literature are demonstrated only on laboratory scale, with scalability, substrate compatibility, and lifecycle performance remaining largely unvalidated. The review identifies the absence of standardized performance evaluation protocols and the fragmentation of structure–property data across studies as key barriers to systematic progress, and proposes that future work prioritize the development of integrated processing–modification–performance frameworks to guide the rational design of next-generation lacquer-based functional materials. Full article

Ambient-temperature asphalt binders have emerged as a sustainable alternative to traditional hot-mix asphalt, offering significant advantages in energy conservation and emission reduction. This review systematically examines the research progress and development trends of high-performance reactive asphalt binders designed for ambient-temperature application, which achieve enhanced performance through chemical cross-linking reactions. The study focuses on three core material systems: epoxy resin, waterborne epoxy emulsified asphalt, and polyurethane. For each system, we comprehensively summarize the material composition, strength formation mechanisms, and mix design methodologies. Key evaluation methods for critical pavement performance—including strength characteristics, water stability, and high-temperature performance—are critically reviewed. Furthermore, microscopic characterization techniques including scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) are discussed to elucidate the underlying mechanisms governing performance evolution. Analysis reveals that epoxy-based binders exhibit superior strength and stiffness, rendering them suitable for heavy-traffic pavements; waterborne epoxy emulsified asphalt binders combine environmental compatibility with construction convenience for thin-layer rehabilitation, while polyurethane-based binders demonstrate exceptional elasticity and rapid curing characteristics for quick-traffic-opening scenarios. Although current research has established a preliminary performance evaluation framework, the absence of unified technical standards constrains widespread engineering implementation. Future research priorities should focus on developing water-triggered curing systems, intelligent responsive materials, and comprehensive standardization systems to fully harness the engineering potential of these sustainable binders. Full article

Liquid electrolytes in conventional lithium-ion batteries pose safety risks associated with flammability, leakage, and explosion, whereas solid polymer electrolytes are generally limited by insufficient ionic conductivity at ambient temperature, restricting the development of high-energy lithium batteries. To address these issues, flexible poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolyte membranes (GPEs) were prepared via a slit-coating process combined with UV curing. NASICON-type lithium aluminum titanium phosphate (Li_1.3Al_0.3Ti_1.7P₃O₁₂, LATP) and garnet-type tantalum-doped lithium lanthanum zirconate (Li_6.4La₃Zr_1.4Ta_0.6O₁₂, LLZTO) were introduced as inorganic ceramic fillers to improve the ion-transport and interfacial properties of the GPE. Among the investigated samples, the PVDF-HFP-based GPE containing 10 wt% LLZTO exhibited the best overall performance, with an ionic conductivity of 3.40 × 10⁻⁴ S·cm⁻¹ at ambient temperature and a Li⁺ transference number of 0.77. Cyclic voltammetry results showed that the LLZTO-modified electrolyte membrane exhibited sharper and more symmetric redox peaks, higher peak current response, and better curve overlap during repeated cycles, indicating improved electrochemical reversibility and interfacial stability. In addition, LLZTO incorporation enhanced the mechanical strength, broadened the electrochemical stability window, and improved the flame-retardant behavior of the membrane. The LiFePO₄/GPE/Li cell assembled with the optimized membrane delivered an initial discharge capacity of 160 mAh·g⁻¹ at 0.1 C and maintained 80 mAh·g⁻¹ at 1 C, demonstrating good rate capability. Moreover, a capacity retention of 96% was maintained after 100 cycles at 0.1 C, confirming excellent cycling stability. Therefore, this work provides an effective strategy for the structural optimization and scalable preparation of high-performance gel polymer electrolyte membranes for lithium battery applications. Full article

The successful realization of a circular economy in the cement industry, coupled with a substantial reduction in carbon emissions, relies on the development of sustainable alternative binder systems. This study investigated the physicomechanical performance and sulfate resistance of composites produced by alkali activation of natural perlite and blast furnace slag. The aim of the research was to improve mechanical properties under low- and medium-alkalinity conditions (5–10 M NaOH). The samples were cured at an ambient temperature of 20 °C and then treated with heat at 60 °C. These samples were then mechanically processed and subjected to five soak–dry cycles in 5% and 10% Na₂SO₄ solutions. The results showed that heat treatment resulted in the formation of a dense C-A-S-H gel, increasing compressive strength approximately eightfold, from 11.64 MPa to 92 MPa. However, perlite’s porous and brittle structure limits its flexural strength to 0.27 MPa; this value is insufficient for structural applications. Under severe sulfate attack (10% Na₂SO₄), samples cured at ambient temperature showed a 12% mass increase in the first cycle due to solution infiltration into capillary voids. As a consequence of extensive ettringite and gypsum formation, the specimens experienced severe deterioration, resulting in a complete loss of mechanical integrity and a residual compressive strength of 0 MPa. In contrast, heat-treated samples showed limited ion diffusion due to a denser matrix and an improved aggregate interface transition zone, resulting in a 2.6% mass increase and a residual compressive strength of 5.17 MPa. Consequently, the obtained findings indicate that thermally treated alkali-activated slag–perlite composites exhibit high resistance against sodium sulfate attack and may have potential for use in specific industrial environments with high sulfate concentrations. However, the performance of these materials under more complex aggressive conditions, such as mining environments involving magnesium sulfate exposure and acidic drainage waters, should be further validated through future studies. Full article

Thermal cracking due to hydration heat in massive monolithic walls poses a significant risk, but traditional prediction methods are often too complex for rapid engineering assessments. This study aims to develop machine learning models to predict the maximum temperature and center-to-surface temperature difference in hardening massive walls, considering variable heat exchange, concrete hardening rate, and formwork curing time. A dataset of 855,360 numerical experiments was collected by solving the transient heat conduction equation using the finite element method (FEM), varying wall thickness, initial and ambient temperatures, heat transfer coefficient, hardening rate, curing time, and heat release. CatBoost gradient boosting regression models were trained and validated to predict both output parameters. The models achieved high accuracy with coefficients of determination exceeding 0.99 for both targets, mean absolute percentage errors of 0.2% for maximum temperature and 3% for temperature difference. Feature importance analysis revealed that heat release dominates both predictions (35–43% importance), followed by wall thickness. The developed CatBoost models enable rapid, accurate prediction of thermal regimes in massive monolithic walls without time-consuming finite element simulations, offering a practical tool for assessment of early cracking risk temperature indicators during construction. Full article

This study explores the real-time aging of a 15-year-old uncalcined kaolinite-based geopolymer (UKG). The significance of this research lies in the fact that uncalcined kaolinite-based geopolymer is a relatively new material tailored for diverse applications, including construction, water treatment, and waste stabilization. While some studies have investigated its durability through accelerated tests, observing its aging over 15 years is essential for its commercial use and field deployment. The specimens were prepared from kaolinite, silica sand, sodium hydroxide, and water. The mixture was molded, compacted, and cured at 80 °C for 24 h to produce a stable geopolymer. Some samples were stored under ambient conditions, while others were immersed; both groups were left for 15 years. After this period, tests evaluated their mechanical, physical, and microstructural properties using XRD, EDS, and SEM. The samples stored under ambient conditions exhibited properties comparable to those of the unaged specimens. In contrast, the immersed samples were unstable, experienced mass loss, showed a sharp decline in strength, and displayed significant microstructural and phase changes. This study suggests adding an extra curing step, such as steaming (hydrothermal) or immersion in alkaline solutions, to enhance the long-term stability of geopolymer binder under immersion conditions. Full article

A comprehensive study was conducted to develop structurally robust, crack-suppressed superhydrophilic nanocomposite coatings comprising poly(acrylic acid) (PAA) and silica nanoparticles. We systematically investigated the critical trade-off between particle loading, which drives surface wettability and stress-induced crack formation driven by capillary forces and shrinkage mismatch. Our findings identify a distinct structural failure threshold between 25 and 30 vol.% silica under conventional drying. By strategically optimizing drying kinetics (an initial flash-dry at 120 °C for 1 h followed by a 24 h ambient cure), we successfully fabricated transparent, crack-suppressed superhydrophilic coatings at elevated silica loadings up to 47 vol.%, establishing a practical, scalable framework for advanced functional surface engineering. The crack-suppressed mechanism was hypothesized to be related to internal stress. Full article

Tile adhesive mortars are industrialized products used for installing ceramic coverings and are classified according to the Brazilian standard ABNT NBR 14081/2012 on the basis of tensile adhesion performance under different curing conditions. Their formulation directly affects both technical performance and manufacturing competitiveness, while conventional product development remains slow, costly and strongly dependent on trial-and-error laboratory testing. This study evaluates whether historical industrial formulation data can support the retrospective prediction of approval or failure of tile adhesive mortars under ambient, oven, immersed and open-time curing conditions. A dataset comprising 6031 individual pull-off observations collected between 2021 and 2023 by a European multinational company in the construction materials sector was used to train and compare Logistic Regression, Random Forest, Boosted Decision Tree and Support Vector Machine models in R and Azure. The study was designed as an industrial-data modelling investigation rather than as a prospective optimization experiment. The results show that ensemble tree-based models, particularly Boosted Decision Tree and Random Forest, achieved the strongest predictive performance, whereas Logistic Regression remained more suitable for inferential interpretation of formulation variables. Model performance was uneven across curing conditions: prediction was more reliable for oven and immersed curing, whereas ambient curing and open time were affected by strong class imbalance and low failure prevalence. The findings indicate that Machine Learning can support formulation screening and quality-oriented decision-making for tile adhesive mortars, provided that its use remains restricted to the formulation ranges represented in the historical dataset and is complemented by prospective experimental validation before deployment in new product development. Full article

Polyurethane (PU) mixtures are a promising high-strength, rapid-curing alternative to conventional asphalt, but their widespread application is hindered by slow curing rates and sensitivity to ambient moisture. To address these limitations, this study systematically evaluated the efficacy of three additives—lignin-based fiber, Glauber’s salt, and green vitriol—in regulating the curing behavior and performance of PU mixtures. Marshall stability, volumetric properties, and moisture resistance were measured under both outdoor and controlled laboratory curing conditions. Lignin fiber uniformly accelerates early-stage curing by enhancing moisture distribution via capillary action. Glauber’s salt releases crystalline water, drastically boosting early-age strength (by 162.4% after 2 days) but at the cost of an increased air void content (up to 8.1%) and reduced long-term water stability (residual stability <80%). Green vitriol acts through Fe²⁺ catalysis and crystalline water release, with its effectiveness being highly temperature- and delay-time-dependent. Combining fiber with Glauber’s salt yields the highest early strength but the shortest construction window (<1 h) and the most severe volumetric deterioration beyond the optimal delay time. All mixtures achieved high ultimate strength after sufficient curing (7 days), but the improvement varied significantly with additive type—ranging from 52.2% (fiber alone) to 162.4% (Glauber’s salt alone). Moreover, even under ideal curing, incomplete –NCO conversion persisted, indicating intrinsic cross-linking limitations. The residual stability of all mixtures fell below the 80% specification for conventional asphalt, suggesting that this metric alone is insufficient for assessing the moisture resistance of high-strength PU mixtures. This study demonstrates that while additives significantly enhance early-age performance, their application requires carefully optimized dosage, delay time, and temperature control to balance early strength gains with long-term volumetric integrity and durability. The findings provide revised evaluation metrics and practical guidelines for implementing PU mixtures in rapid pavement construction and repair. Full article

The addition of sulfoaluminate cement (SAC) to ultra-high-performance concrete (UHPC) enables sustainable high-speed construction due to the high 7-day strength without thermal curing. The fast hydration of SAC, however, endangers the admixture efficacy, which may compromise the structural integrity of the infrastructure components. This study investigates the effect of the physical form of polycarboxylate ether (PCE) superplasticizers on the performance of UHPC with the incorporation of SAC in ambient conditions. A paired experimental design of 32 mixtures compared liquid superplasticizers (LSPs) and powder superplasticizers (PSPs) in various binder compositions (OPC/SAC of 1/4–4/1) and water-to-binder ratios (0.18–0.21) at a constant dosage of admixtures of 1% except where w/b 0.18 (1.5% superplasticizers and 1% retarders were used). Findings indicate that LSPs enhance workability and compressive strength by 45% and 10.03%, respectively. The underlying mechanism is explained by comprehensive microstructural characterization through the use of Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. SEM study showed a 23% decrease in porosity, and XRD patterns showed the increased formation of amorphous C-S-H gel for LSPs. The higher levels of Al³⁺ incorporated into the gel structure (C-A-S-H) of the liquid forms was also verified by FTIR spectra. Mechanically, the research reveals one of the kinetic mismatches, where the rate of SAC hydration is greater than the rate of powder dissolution, which leads to a failure to fully disperse and shear-controlled failures. LSPs, in contrast, make it possible to disperse particles immediately, so the matrices become more dense and shift to axial failure. These results provide practical guidelines to infrastructure engineers to use liquid superplasticizer in SAC-based systems in order to achieve sustainability and reliability in terms of performance in precast and fast-track construction projects. Full article

Direct current (DC) surface flashover on polystyrene (PS) remains a critical bottleneck that impedes its reliable application in high-voltage insulation apparatus. To circumvent the protracted processing durations and stringent film-forming conditions inherent in conventional surface modification techniques, this study proposes a novel “liquid-film-assisted in situ rapid plasma curing” strategy. By harnessing atmospheric-pressure dielectric barrier discharge (DBD) technology within an argon ambient, the rapid (<6 min) and efficient deposition of a fluorosilane (FAS-13) functional coating onto the substrate was achieved. Microscopic characterizations coupled with isothermal surface potential decay (SPD) measurements reveal that this coating substantially mitigates the detrapping and surface migration of charge carriers. Macroscopic DC flashover testing corroborates that, under the optimal modification ratio, the surface breakdown voltage of PS is elevated to 14.04 kV, yielding an insulation gain of 26.94%. To elucidate the underlying physical mechanisms, density functional theory (DFT) calculations were conducted, revealing that the energy band misalignment between the wide-bandgap fluorinated layer and the substrate facilitates the construction of a high-density deep trap network (with a depth of ~0.8 eV) at the coating–substrate interface. By robustly anchoring primary electrons and inducing the formation of a homopolar space charge shielding layer, these deep traps physically arrest the evolution of the secondary electron emission avalanche (SEEA). Consequently, this work not only establishes a viable engineering framework for the rapid, large-scale surface reinforcement of DC insulation equipment but also provides profound quantum chemical insights into interfacial trap regulation within all-organic dielectrics. Full article

This study develops a ternary Fe-based geopolymer system composed of metakaolin (MK), red mud (RM), and fly ash (FA) for the preparation of sustainable water-retaining subgrade materials for sponge-city roadbed applications. Unlike conventional formulations primarily designed for structural strength or rapid permeability, the proposed MK–FA–RM system was designed to improve water-storage capacity while maintaining adequate mechanical support and environmental compatibility. In this ternary system, MK provides highly reactive aluminosilicate species for geopolymer network formation, RM introduces Fe-bearing phases and enhances industrial solid-waste utilization, and FA contributes to particle packing, workability, and resource efficiency. A constrained ternary mixture design implemented using Design-Expert software was adopted to optimize precursor proportions. Within the investigated compositional range, the fitted first-order mixture model showed acceptable statistical adequacy for preliminary composition screening (R² = 0.86). The optimal blend (60% MK, 30% RM, and 10% FA) achieved a 7-day compressive strength of 8.37 MPa and a water retention rate of 35.3% under ambient curing conditions, satisfying the strength requirement considered for the target subgrade/base-layer application. Microstructural and phase analyses suggest that the synergistic interaction of the three precursors promoted Fe-modified aluminosilicate gel formation together with conventional geopolymer gel products, while improving matrix continuity and preserving interconnected pore space for water storage. This multiscale structural effect helps explain how the material achieved a balance between water retention capacity and mechanical support. Under the tested conditions, the material maintained acceptable residual strength after short-term exposure to water, acid, and sulfate-containing solutions. Life-cycle assessment indicated a 70% reduction in CO₂ emissions compared with ordinary Portland cement, while pilot-scale cost analysis showed a 39% lower production cost than MetaMax-based geopolymer materials. Pilot-scale application further demonstrated the constructability and water-regulation potential of the material in practical environments. Overall, the proposed ternary Fe-based geopolymer demonstrates that Fe-rich industrial wastes can be engineered into low-carbon and economically viable water-retaining subgrade materials that balance hydraulic regulation, structural adequacy, and sustainability. Nevertheless, long-term durability, cyclic loading performance, and direct nanoscale characterization of Fe-bearing gel evolution still require further investigation. Full article

In architecture and construction, it is common practice to use acrylic products with a high flammable content, ranging from lacquers designed to improve the curing of concrete and mortar to resins that provide protection, sealing, flexibility, and elasticity. The drying process of the treated surface involves the formation of vapours of volatile organic compounds (VOCs); to prevent these from creating a potentially hazardous flammable atmosphere, a procedure is presented that establishes the maximum application rate for solvent-based products, providing equations that relate the maximum application area and the minimum drying time to the available air velocity in the work area. The results are provided for both indoor and outdoor applications. A maximum application rate is established to prevent the creation of areas classified as fire or explosion hazards: 1.5 m²/h indoors and 1 m²/h outdoors. When this is carried out at an ambient temperature of 20 °C, and from 40 °C upwards, it is not possible to apply the varnishes in practice without creating a flammable atmosphere. Full article

Polyurea elastomers are widely used in industry thanks to their exceptional mechanical properties. However, cold-pour systems typically require extended ambient curing times to achieve optimal performance. This study investigates whether accelerated thermal curing can replicate or exceed the mechanical properties obtained through the standard ambient cure protocol. Specimens were prepared by hand-mixing and then cured at temperatures of 50 $°\mathrm{C}$ and 70 $°\mathrm{C}$ for 1 h, 3 h and 6 $\mathrm{h}$. Selected specimens were then aged at room temperature for up to 7 d. Uniaxial tensile tests were conducted, with strain measured via a video-tracking technique. Porosity analysis was performed using cross-section micrographs. The results show that a 6 $\mathrm{h}$ cure at 50 $°\mathrm{C}$ yields mechanical properties comparable to those obtained through the standard ambient cure, while a 6 $\mathrm{h}$ cure at 70 $°\mathrm{C}$ significantly surpasses them. Post-cure aging was found to be particularly effective for specimens with a thickness of 1.5 $\mathrm{m}$$\mathrm{m}$, achieving a tensile strength of 4.7 $\mathrm{M}$$\mathrm{Pa}$ after 7 d, exceeding that declared by the manufacturer. Full article