Search Results (75)

Tribological processes in extreme environments pose serious material challenges, requiring coatings that resist both wear and corrosion. This review summarizes recent advances in protective coatings engineered for extreme environments such as high temperatures, chemically aggressive media, and high-pressure and abrasive domains, as well as cryogenic and space applications. A comprehensive overview of promising coating materials is provided, including ceramic-based coatings, metallic and alloy coatings, and polymer and composite systems, as well as nanostructured and multilayered architectures. These materials are deployed using advanced coating technologies such as thermal spraying (plasma spray, high-velocity oxygen fuel (HVOF), and cold spray), chemical and physical vapor deposition (CVD and PVD), electrochemical methods (electrodeposition), additive manufacturing, and in situ coating approaches. Key degradation mechanisms such as adhesive and abrasive wear, oxidation, hot corrosion, stress corrosion cracking, and tribocorrosion are examined with coating performance. The review also explores application-specific needs in aerospace, marine, energy, biomedical, and mining sectors operating in aggressive physiological environments. Emerging trends in the field are highlighted, including self-healing and smart coatings, environmentally friendly coating technologies, functionally graded and nanostructured coatings, and the integration of machine learning in coating design and optimization. Finally, the review addresses broader considerations such as scalability, cost-effectiveness, long-term durability, maintenance requirements, and environmental regulations. This comprehensive analysis aims to synthesize current knowledge while identifying future directions for innovation in protective coatings for extreme environments. Full article

The fatigue resistance of cement-stabilized macadam (CSM) plays a vital role in ensuring the long-term durability of pavement structures. However, limited cementitious material (CM) content often leads to high packing voids, which significantly compromise fatigue performance. Existing studies have rarely explored the coupled mechanism between pore structure and fatigue behavior, especially in the context of solid-waste-based CMs. In this study, a cost-effective alkali-activated sludge gasification slag (ASS) was proposed as a sustainable CM substitute for ordinary Portland cement (OPC) in CSM. A dual evaluation approach combining cross-sectional image analysis and fatigue loading tests was employed to reveal the effect pathway of void structure optimization on fatigue resistance. The results showed that ASS exhibited excellent cementitious reactivity, forming highly polymerized C-A-S-H/C-S-H gels that contributed to a denser microstructure and superior mechanical performance. At a 6% binder dosage, the void ratio of ASS–CSM was reduced to 30%, 3% lower than that of OPC–CSM. The 28-day unconfined compressive strength and compressive resilient modulus reached 5.7 MPa and 1183 MPa, representing improvements of 35.7% and 4.1% compared to those of OPC. Under cyclic loading, the ASS system achieved higher energy absorption and more uniform stress distribution, effectively suppressing fatigue crack initiation and propagation. Moreover, the production cost and carbon emissions of ASS were 249.52 CNY/t and 174.51 kg CO₂e/t—reductions of 10.9% and 76.2% relative to those of OPC, respectively. These findings demonstrate that ASS not only improves fatigue performance through pore structure refinement but also offers significant economic and environmental advantages, providing a theoretical foundation for the large-scale application of solid-waste-based binders in pavement engineering. Full article

Hydraulic concrete is subject to severe durability challenges when abraded by the high-speed flow of sandy water. Conventional concrete frequently needs to be repaired because of its high brittleness and insufficient abrasion resistance, while granular rubber can easily be dislodged from the matrix during abrasion, forming a new source of abrasion and increasing the damage to the matrix. For this reason, we used fibrous rubber concrete to systematically study the mechanisms of the influence of the dosage of nitrile rubber (5%, 10%, and 15%) and fiber length (6, 12, and 18 mm) on resistance to impact and abrasion performance. Through mechanical tests, underwater steel ball abrasion tests, three-dimensional morphology measurements, and fractal dimension analysis, the law behind the damage evolution of fibrous rubber concrete was revealed. The results show that concrete with 15% NBR and 12 mm fibers yielded the best performance, and its 144-hour abrasion resistance reached 25.0 h/(kg/m²), which is 163.7% higher than that for the baseline group. Fractal dimension analysis (D = 2.204 for the optimum group vs. 2.356 for the benchmark group) showed that the fiber network effectively suppressed surface damage extension. The long-term mass loss rate was only 2.36% (5.82% for the benchmark group), and the elastic energy dissipation mechanism remained stable under dynamic loading. The results of a microanalysis showed that the high surface roughness of NBR enhances interfacial bonding, which synergizes with crack bridging and stress dispersion and, thus, forms a multiscale anti-impact abrasion barrier. This study provides a new material solution for the design of durable concrete for use in high-impact and high-abrasion environments, which combines mechanical property preservation and resource recycling value. However, we did not systematically examine the evolution of the performance of fiber rubber concrete concrete under long-term environmental coupling conditions, such as freeze–thaw cycles, ultraviolet aging, or chemical attacks, and there are limitations to our assessment of full life-cycle durability. Full article

As the severe environmental impacts of plastic pollution demand determined action, the European Union (EU) has included recycling at the core of its policies. Consequently, evolving jurisdiction now aims to achieve a recycling rate of 65% for non-PET plastic bottles by 2040. However, the widespread use of post-consumer high-density polyethylene (rPE-HD) recyclates in household chemical containers is still limited by PP contamination, poor mechanical properties, and low environmental stress cracking resistance (ESCR). Although previous studies have explored the improvement of regranulate properties through additives, few have examined whether reducing the variety of extrusion blow-moulded PE-HD packaging could offer similar benefits. Therefore, two sorted fractions of rPE-HD hollow bodies were processed into regranulates under industrial conditions, including hot washing, extrusion, and deodorisation. Subsequently, both materials underwent comprehensive characterisation regarding their composition and performance. The opaque material, which was sourced from milk bottles in the UK, exhibited greater homogeneity with minor impurities, leading to improved ductility and melt strain hardening at moderate strain rates compared to the mixed material stream, which contained approximately 2.5% PP contamination. However, both rPE-HD recyclates exhibited similar short-term creep behaviour, relatively low strain hardening moduli, and were almost devoid of inorganic particles. Considering the sum of the investigated properties, melt blending with suitable virgin material is likely one of the most effective options to maximise regranulate utilisation in hollow bodies, followed by recycling-oriented packaging design (e.g., for efficient sorting), and the employment of advanced sorting technology. Full article

The HVOF (High Velocity Oxy-Fuel) thermal spraying method is widely used in surface engineering to produce coatings with high hardness, low porosity, and excellent crack resistance. Composite coatings with chromium carbide (Cr₃C₂) in a nickel–chromium (NiCr) matrix are commonly applied in demanding environments, such as the energy and transport sectors. This study compares the microstructure, mechanical, tribological, and corrosion properties of two coatings—Cr₃C₂-25(Ni20Cr)-10(Ni) and Cr₃C₂-25(Ni20Cr)—deposited on ductile cast iron using HVOF. The addition of 10 wt.% Ni enhances coating integrity, mechanical performance, and environmental resistance by improving ductility, reducing residual stress, enhancing wettability, and balancing hardness with improved crack, wear, and corrosion resistance. Microstructure analysis via LM (Light Microscopy) and SEM (Scanning Electron Microscopy), along with chemical and phase characterization using EDS (Energy Dispersive X-ray Spectroscopy) and XRD (X-ray Diffraction), revealed that the Ni-enriched Cr₃C₂-25(Ni20Cr)-10(Ni) coating exhibited a denser structure, lower porosity, and high hardness. Its microstructure consists of large, partially melted Ni particles and fine Cr₃C₂ and Cr₇C₃ carbides embedded in the NiCr matrix, some at submicron scales. Performance tests, including indentation (H_IT, E_IT, K_IC), scratch, and corrosion resistance assessments, confirmed that Ni addition improves crack resistance, wear durability, and corrosion protection. Consequently, these coatings demonstrate superior operational durability, making them more effective in challenging environments. Full article

Ni-based superalloys with enhanced environmental resistance at high temperatures are crucial for advanced gas turbine engines. The new polycrystalline nickel-based superalloy has excellent mechanical properties, but as a low-Cr, high-alloying superalloy, its environmental resistance has never been investigated. The hot corrosion behavior of the nickel-based superalloy under molten salt conditions and its effect on its tensile properties were investigated in this paper. The results showed the following: The diffusion of the Cr, Al, and Ni elements governs the majority of the corrosion process, resulting in the production of an environmentally damaged organization with internal sulfidation and surface oxidation. The Wagner model predicts the inability to form a dense Al oxide scale on the surface because the crucial generation condition of external Al oxides is not met. In addition, the growth stress in the damage scales is the main cause of cracking and spalling in the isothermal corrosion process. Due to the increased local stress concentration brought on by this environmental degradation, the sulfide scale acts as a fracture source, guiding the matrix cracking and influencing the tensile properties of the alloy. Full article

Circular hollow sections (CHSs) are widely used in offshore jacket structures due to their excellent compressive strength, torsional resistance, and direction-independent stiffness. However, CHS joints are prone to fatigue-induced cracking caused by complex geometries, environmental loading, and aging. Fatigue crack propagation, governed by the stress intensity factor (SIF), threatens structural integrity if the SIF exceeds fracture toughness. Composite reinforcement has emerged as a promising solution for mitigating crack propagation and enhancing joint performance. This study presents a numerical parametric investigation of fatigue-cracked tubular T-joints, focusing on the effects of crack size, crack location, and composite reinforcement on the SIF under various loading conditions. The highest SIF was consistently observed at the saddle point in T-joints under axial and out-of-plane bending (OPB) loads. However, in T-joints subjected to in-plane bending (IPB) loads, the highest SIF was found between the crown and saddle points. The SIF increased with the size and diameter of the cracks. The application of CFRP wrapping was found to reduce the SIF by more than 50% across all loading conditions, with the most significant reductions observed when the reinforcement was oriented along the chord axis. Full article

Reflection cracks significantly compromise the service life of half-rigid asphalt pavements in cold regions. This study introduces SAKIII warm-mixed rubber–asphalt mixture (SAKIII WMRA Mix) as a stress absorption layer to address this issue. Through orthogonal tests, regression analysis, and performance comparisons with SBS-modified asphalt, the material composition, low-temperature cracking resistance, and fatigue performance of WMRAM were systematically evaluated. The results show that SAKIII WMRA Mix maintains superior road performance with 30 °C lower mixing/compaction temperatures compared to traditional hot-mix asphalt mixture. At −10 °C, its low-temperature cracking resistance improves by 40% and fatigue life extends by 35% over the SBS-modified asphalt mixture. Mechanistically, SAKIII WMRA Mix reduces reflection crack propagation by 30% and prolongs pavement service life by over 25% under equivalent traffic/climate conditions. Additionally, it decreases energy consumption by 15–20% and provides a sustainable solution for cold-region road construction. This research establishes optimized mix design methods and performance criteria for WMRAM, offering theoretical support and practical guidance for reflective crack mitigation in cold climates. The proposed technology effectively balances mechanical properties, energy efficiency, and environmental benefits, making it especially suitable for cold areas where thermal stress dominates road damage. Full article

In order to utilize a large amount of waste scallop shells in road engineering and develop environmentally friendly and high-performance asphalt, the impact of scallop shell powder (SSP) on the high temperature performance of base asphalt and styrene-butadiene-styrene (SBS)-modified asphalt was evaluated in this study. The effects of SSP on the conventional properties of base asphalt and SBS-modified asphalt were investigated according to penetration, softening point, ductility, and rotational viscosity at 135 °C, and recommended dosing amounts were given, respectively. The high-temperature rheological properties of SSP-modified asphalt were evaluated according to temperature sweep and multiple stress creep and recovery (MSCR) tests. The modification mechanism of SSP-modified asphalt was analyzed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results indicated that an appropriate amount of SSP can effectively improve the consistency and shear deformation resistance of base asphalt and SBS-modified asphalt but can also affect the ductility and fatigue cracking resistance. The recommended weight amounts of SSP in base asphalt and SBS-modified asphalt were 9% and 12%, respectively. Moreover, SSP can improve the thermal stability and resistance to permanent deformation of asphalt, but excessive SSP may weaken the improvement effect of the high-temperature rheological properties of asphalt. The SSP is evenly distributed and tightly combined with asphalt at an appropriate amount, and the modification process of asphalt mainly involves physical changes. Full article

In this study, the finite element analysis software MIDAS FEA NX was used to simulate and analyze the concrete, and the temperature regulation effect of phase change materials in concrete and its influence on crack resistance was discussed. A 1/8 concrete specimen model was constructed, and different ambient temperatures (5 °C to 35 °C) and concrete material parameters were set. Through simulation, it is found that phase change materials can effectively absorb environmental heat, maintain the temperature stability of concrete structures, and reduce the internal temperature peak. In addition, the addition of phase change materials can also reduce the temperature difference between the inside and outside of concrete, relieve the internal stress and improve the crack resistance of concrete. The results show that under different construction temperatures, the phase change concrete can quickly achieve the consistency of internal and external temperature and stress, reduce the cracking problem, and show good temperature regulation and crack resistance. Full article

This study investigates the durability of concrete structures under severe environmental conditions, focusing on the effects of thermal stress, saline exposure, and seismic activity. The research employs a dual approach, combining laboratory experiments and field case studies to analyze various environmental impacts, mix designs, and the use of crystalline admixtures. Two concrete mix designs, CMD-01-C30/37 (mass concrete) and CMD-02-C35/45 (underwater concrete), were developed and tested for strength, permeability, and self-healing properties. The results demonstrate that both mix designs met or exceeded the required strength specifications, with improved resistance to water penetration and permeability depths lower than the code requirements set by European standards from EC2. The incorporation of crystalline admixtures in the mix designs significantly enhanced durability and performance, aligning with the priority of developing zero-carbon concrete solutions. The study also observed the self-healing capabilities of concrete treated with crystalline admixtures, as evidenced by the sealing of cracks at expansion and construction joints over time. These findings contribute to the development of a robust methodology for creating resilient structures adaptable to climate change, with potential implications for enhancing seismic resistance and structural longevity. The study underscores the importance of considering environmental factors and innovative admixtures in concrete design to improve durability and resilience, particularly in areas prone to seismic activity and extreme environmental conditions. Future research directions should focus on further investigating self-healing mechanisms, exploring the integration of durable and self-healing cement-based materials in engineering practice, and evaluating applications for both new construction and retrofitting existing structures. Full article

The degradation of rubber materials under environmental and mechanical stress presents a significant challenge, particularly due to UV (ultraviolet light) exposure, which severely impacts the material’s physical properties. This study aims to enhance the UV stability and longevity of rubber by evaluating the performance of modified polyurethane and silicone coatings as protective stabilizers. Natural rubber—styrene–butadiene rubber (NR-SBR), known for its exceptional mechanical properties, was selected as the base material. To ensure strong adhesion, cold atmospheric plasma treatment was applied, increasing the surface energy by 250%, primarily through an enhancement of the polar component. After treatment, supplier-recommended coatings were applied and tested for adhesion using the pull-out method. Aging tests under UV exposure, water immersion, and high temperatures were conducted to assess durability, with tensile tests used to monitor changes over time. Coatings exhibiting cracking after UV exposure were excluded from further analysis. A silicone coating demonstrating superior moisture resistance and durability under extreme conditions was identified as a promising candidate for future UV stabilization applications. These findings provide a foundation for developing advanced coatings to significantly extend the service life of rubber materials in demanding environments. Full article

The advantages of asphalt pavement in terms of driving comfort, construction efficiency, and ease of maintenance have established it as the predominant choice for high-grade pavements at present. However, being highly sensitive to temperature and stress, asphalt performance is significantly influenced by external environmental conditions and loading, making it susceptible to various distress phenomena. Particularly in high-latitude regions, asphalt pavement cracking severely limits asphalt pavement’s functional performance and service lifespan under cold climatic conditions. To enhance the low-temperature cracking resistance of asphalt pavement in cold regions, tools such as VOS viewer 1.6.20 and Connected Papers were utilized to systematically organize, analyze, and summarize relevant research from the past 40 years. The results reveal that temperature shrinkage cracks and thermal fatigue cracks represent the primary forms of asphalt pavement distress in these regions. Cracking in asphalt pavement in cold regions is primarily influenced by structural design, pavement materials, construction technology, and climatic conditions. Among these factors, surface layer stiffness, base layer type, and the rate of temperature decrease exert the most significant impact on cracking resistance, collectively accounting for approximately 45.4% of all cracking-related factors. The low-temperature performance of asphalt pavement can be effectively improved through several strategies, including adopting full-thickness asphalt pavement with a skeleton-dense structure or reduced average particle size, incorporating functional layers, appropriately increasing the thickness of the upper layer and the compaction temperature of the lower layer, utilizing continuous surface layer construction techniques, and applying advanced materials. High-performance modifiers such as SBR and SBS, nanomaterials with good low-temperature performance, and warm mixing processes designed for cold regions have proven particularly effective. Among various improvement methods, asphalt modification has demonstrated superior effectiveness in enhancing the deformation capacity of asphalt and its mixtures, significantly boosting the low-temperature performance of asphalt pavements. Asphalt modification accounts for approximately 50% of the improvement methods evaluated in this study, with an average improvement in low-temperature performance reaching up to 143%. This paper provides valuable insights into the underlying causes of cracking distress in asphalt pavements in cold regions and offers essential guidance for improving the service quality of such pavements in these challenging environments. Full article

The substitution of virgin asphalt binder with reclaimed asphalt pavement (RAP) has environmental and economic merits, however, cracking susceptibility arises due to the aged asphalt binder within RAP. The objectives of this study are to (1) enhance the cracking resistance of asphalt mixtures containing 50% RAP utilizing recycling agents (RAs) derived from six petroleum-based and bio-based materials, (2) conduct an environmental impact assessment (represented by global warming potential “GWP”) for high-RAP mixtures including RAs, and (3) estimate the cost effectiveness of including high-RAP content in asphalt mixtures. Based on the RAP asphalt binder performance grade (PG), base asphalt binder PG, and RAP content, the RA contents were determined to achieve a target asphalt binder of PG 76-22. A control mixture was benchmarked for comparison, specified for high-traffic volume roads, and contained PG 76-22 polymer-modified asphalt binder. The engineering performance of studied asphalt mixtures was evaluated using the Hamburg wheel-tracking (HWT), semi-circular bend, Illinois flexibility index, Ideal cracking tolerance, and thermal stress-restrained specimen tensile strength tests. It was found that petroleum-derived aromatic oil, soy-based oil, and tall oil fatty acid-based RAs demonstrated a successful restoration of aged RAP asphalt binder without compromising the permanent deformation resistance. The 50% RAP mixtures emitted less GWP by 41% and 42.9% using petroleum- and bio-oil RAs, respectively, and achieved a 31% cost reduction compared to the control mixtures. Full article

The application of nanomaterials as modifiers in the field of asphalt is increasingly widespread, and this paper aims to systematically review research on the impact of nanomaterials on asphalt viscosity. The results find that nanomaterials tend to increase asphalt’s viscosity, enhancing its resistance to high-temperature rutting and low-temperature cracking. Zero-dimension nanomaterials firmly adhere to the asphalt surface, augmenting non-bonding interactions through van der Waals forces and engaging in chemical reactions to form a spatial network structure. One-dimensional nanomaterials interact with non-polar asphalt molecules, forming bonds between tube walls, thereby enhancing adhesion, stability, and resistance to cyclic loading. Meanwhile, these bundled materials act as reinforcement to transmit stress, preventing or delaying crack propagation. Two-dimensional nanomaterials, such as graphene and graphene oxide, participate in chemical interactions, forming hydrogen bonds and aromatic deposits with asphalt molecules, affecting asphalt’s surface roughness and aggregate movement, which exhibit strong adsorption capacity and increase the viscosity of asphalt. Polymers reduce thermal movement and compact asphalt structures, absorbing light components and promoting the formation of a cross-linked network, thus enhancing high-temperature deformation resistance. However, challenges such as poor compatibility and dispersion, high production costs, and environmental and health concerns currently hinder the widespread application of nanomaterial-modified asphalt. Consequently, addressing these issues through comprehensive economic and ecological evaluations is crucial before large-scale practical implementation. Full article