Search Results (684)

To investigate the elevated-temperature performance of Ultra-High-Performance Concrete (UHPC) and Ultra-High-Performance Geopolymer Concrete (UHPGC), a systematic comparative study was conducted at 800 °C. This study examined the effects of the steel fibre geometry (micro and hooked-end) and dosage (1.5% and 2.0%) on mass loss, crack propagation, residual compressive, flexural, and tensile strengths, and chemical evolution following a 24 h pre-drying protocol to mitigate explosive spalling. The results demonstrate that UHPGC exhibits superior thermal stability and residual mechanical performance compared with UHPC after high-temperature exposure. Among all mixtures, the UHPGC mixture reinforced with 2% micro steel fibres (UHPGC-M2) achieved the highest residual compressive strength (30 ± 0.4 MPa, corresponding to 25% strength retention compared with 21% for the equivalent UHPC mixture), the lowest post-exposure crack width (0.08 mm), and the highest tensile strength retention (17.9%). Micro steel fibres were more effective in controlling crack propagation and preserving peak load capacity, whereas hooked-end fibres contributed more significantly to post-peak ductility. Chemical analysis revealed substantial chemical changes in both systems after exposure to 800 °C. However, UHPGC exhibited lower mass loss (4.8%) and greater residual performance. These findings establish micro steel fibre-reinforced UHPGC as a sustainable and high-performance material for fire-resistant structural applications. Full article

Rising temperatures and the occurrence of heat waves due to climate change can increase the risk of various skin disorders. Moreover, elevated temperatures worsen oxidative damage and inflammation caused by other climate change stressors, such as UV exposure. Consequently, there is growing interest in innovative solutions to protect skin health from the effects of pollution and climate change stressors. Among natural cosmeceuticals, carotenoids are recognized for their antioxidant and anti-inflammatory properties. This study evaluated the thermoprotective effects of Hematococcus lacustris (the microalga formerly called Hematococcus pluvialis) extract (HLE), which is considered the richest natural source of carotenoid astaxanthin, against acute hyperthermia, which mimics the conditions of heat waves. In addition, we separately assessed the effects of HLE against UVA and hydrogen peroxide stress, complementing the antioxidant profile of the extract under study. The evaluation was conducted using in vitro tests on human HaCaT keratinocytes and the nematode Caenorhabditis elegans, which is a model organism sensitive to environmental stressors. The treatment of HaCaT keratinocytes with HLE counteracted the intracellular formation of reactive oxygen species and cytotoxicity induced by hyperthermia, UVA, and hydrogen peroxide exposure. Under the same experimental conditions, HLE also restored the impaired expression of stress-sensitive genes, such as matrix metalloproteinase-1, in HaCaT keratinocytes and promoted wound closure mimicking the process of re-epithelization. Lastly, experiments in C. elegans confirm that HLE reduces heat stress-induced oxidative damage and preserves motility, supporting a systemic protective effect consistent with dietary uptake of the extract. These findings suggest that HLE, rich in carotenoid astaxanthin, can protect keratinocytes against oxidative damage and cytotoxicity induced by thermal stress, indicating its potential role in mitigating thermal aging. Full article

Red mud (RM), a highly alkaline by-product of the alumina refining process, poses significant environmental challenges due to its large-scale accumulation. This study systematically investigates the mechanical performance, thermal resistance, and durability of RM-based cement mortar, evaluating the individual effects of fly ash (FA), basalt fibers (BF), and nano zinc oxide (NZO) as separate modifying constituents introduced independently into the RM matrix. Fourteen mortar mixtures were prepared with RM replacement levels of 10–35%, a constant FA content of 15%, BF dosages of 0.5–1.5%, and NZO dosages of 0.5–2.0%. Workability, 28-day compressive and flexural strengths, residual mechanical properties after exposure to 600 °C and 800 °C, sulfate resistance, and microstructural characteristics were evaluated. Increasing RM content reduced workability and mechanical strength, with compressive and flexural reductions reaching 35.5% and 29.0% at 30% RM, respectively. FA partially compensated through its ball-bearing effect and pozzolanic reactivity. The optimal 1.5% BF dosage increased the compressive and flexural strengths by 14.7% and 37.5%, respectively, and significantly enhanced the residual performance at elevated temperatures. The optimal 0.5% NZO improved the compressive and flexural strengths by 13.2% and 18.3%, respectively; however, 2.0% NZO caused complete strength loss, which may be associated with severe nanoparticle agglomeration and possible zinc-containing reaction products reported in previous studies. The formation of specific crystalline phases was not experimentally verified in the present study. Sulfate resistance deteriorated with increasing RM, whereas 1.5% BF and 1.0% NZO reduced mass loss by 58.9% and 59.7%, respectively. SEM confirmed that RM15 + FA15 exhibited the densest microstructure with minimal voids. The results demonstrate that RM can be effectively utilized as a sustainable cement replacement, with FA, BF, and NZO each independently identified as effective performance-enhancing constituents at their respective optimal dosages; their combined quaternary application remains untested and is proposed as a direction for future validation. Full article

This paper presents a methodology to evaluate the entire process of thermal evolution and fracture failure within stay cables subjected to sheath fires. Computer software FDS 2021 and ABAQUS 2021 are applied to build a sequentially thermos–mechanics coupled method integrating thermal, structural, and fracture dynamic analyses in stay cables under sheath fire exposure conditions. Herein, three representative fire scenarios including full-circumferential, top-side, and bottom-side ignition are reconstructed. Further, 127 individual wires, accounting for interstitial cavity radiation and contact heat transfer, are utilized to perform analysis on sectional temperature in stay cables. The results indicate that the ignition mode dictates the cross-sectional temperature gradient, with localized ignitions inducing highly asymmetric thermal fields and pronounced internal bending moments. Elevated temperatures trigger a progressive load redistribution from the degraded fire-facing wires to cooler internal layers. Ultimately, abrupt global fracture occurs when the residual ultimate load-carrying capacity intersects with the actual applied tension, resulting in a fracture morphology that closely corresponds to the spatial thermal distribution. Furthermore, the structural capacity degradation exhibits three distinct time-dependent stages: a slow degradation stage, a sharp decline stage, and a recovery stage. Among the analyzed scenarios, full-circumferential ignition induces the most drastic overall capacity reduction, while bottom-side ignition poses a markedly greater rupture risk than top-side ignition. Full article

The mechanical behavior of S135 and V150 (Mo-V-Nb microalloyed) drill pipe steels was systematically investigated at room temperature (RT) and elevated temperatures (100–300 °C), alongside the microstructural evolution after long-term thermal exposure at 310 °C (200–500 h). V150 steel exhibits a superior RT yield strength (1099 vs. 1012 MPa) relative to S135, attributed to grain refinement and precipitation strengthening from nanoscale MC precipitates. However, at 200–300 °C, S135 steel displays strength recovery due to dynamic strain aging (DSA) facilitated by the formation of Cottrell atmospheres. Conversely, in V150 steel, V and Nb pin free interstitial atoms, suppressing Cottrell atmosphere formation and DSA. Consequently, V150 cannot gain DSA-induced strengthening, resulting in a steeper yield strength decline (a 17.3% drop at 300 °C versus 11.5% for S135). Long-term thermal exposure further reveals divergent microstructural evolution: S135 steel achieves synchronous improvements in strength and ductility via the transformation of coarse M₃C into stable alloy carbides and the precipitation of nanoscale Mo-enriched carbides. In contrast, V150 steel undergoes Ostwald ripening and coherency loss of high-volume-fraction nano-MC precipitates, weakening dislocation pinning and accelerating dislocation annihilation, ultimately leading to the simultaneous degradation of strength and ductility. This study elucidates that while Mo-V-Nb microalloying enhances RT strength, it compromises high-temperature mechanical stability. Full article

Climate change increasingly threatens Mediterranean ornamental horticulture and green infrastructure through elevated temperatures, prolonged drought conditions, soil salinity, and more frequent extreme weather events. As a result, plant growth, phenology and landscape sustainability are significantly affected. This systematic review aimed to identify and qualitatively synthesize the available evidence on the responses of ornamental plants and their production and end use systems to climate-related stress, with emphasis on Mediterranean native species and their potential contribution to climate-resilient landscaping. The review was conducted and reported in accordance with PRISMA 2020. An adapted Population–Exposure–Outcome framework was used to operationalize the overarching review question and guide eligibility assessment. Scopus and the Web of Science Core Collection were systematically searched for peer-reviewed English-language articles published between 1 January 2001 and 31 May 2026. Eligible publications examined ornamental plants, floricultural species, or native and endemic taxa with potential ornamental or landscape use and addressed climate-related stressors, plant resilience, adaptation strategies, cultivation or propagation practices, green-infrastructure applications, or related ecological trade-offs in Mediterranean-relevant contexts. Two reviewers independently assessed titles, abstracts, and full texts using predefined eligibility criteria. The review used a structured qualitative narrative synthesis organized into thematic domains to systematically identify, select, and synthesize the available evidence. Meta-analysis was not undertaken because of substantial heterogeneity in plant material, environmental stressors, study designs, and reported outcomes. A total of ninety studies were included and organized into five domains: climate stress and plant responses (n = 14), native Mediterranean ornamental species (n = 21), adaptation and resilience strategies (n = 16), urban landscaping and green infrastructure (n = 25), and ecological risks and invasive species (n = 14). The review revealed that several native Mediterranean plants possess morphological, physiological, or ecological characteristics associated with tolerance to drought, salinity, and other climate-related stresses, supporting their potential use in sustainable ornamental horticulture. Water-efficient irrigation, alternative water sources and substrates, nursery preconditioning, non-microbial biostimulants, and genotype or physiological screening showed adaptation potential, but their effectiveness depended on species, genotype, intervention intensity, and application context. Evidence remained limited for compound stresses, combined interventions, nursery-to-landscape transfer, long-term field performance, commercial scalability, and environmental trade-offs. Overall, climate-resilient ornamental horticulture requires the integration of plant selection, propagation, production, controlled stress screening, landscape validation, and ecological-risk assessment. This review proposes an evidence-to-application framework to support research, nursery production, landscape planning, and the responsible deployment of climate-adapted ornamental plants. Full article

Polyamide 66 reinforced with 25 wt.% short glass fibres (PA66-GF25) is widely used in engineering applications requiring long-term operation under combined thermal and lubricated conditions, including polymer bearing cage applications. However, the long-term evolution of its mechanical behaviour under thermo-oil exposure remains insufficiently documented, particularly over extended exposure periods relevant for service-oriented durability assessment. This study investigates the tensile behaviour of PA66-GF25 after immersion in an industrial bearing lubricant for up to 12 months at conditioning temperatures of −30 °C, 24 °C, and 60 °C. Tensile tests were primarily performed at 24 °C to evaluate the influence of conditioning history, while selected specimens were additionally tested at 60 °C to assess the effect of testing temperature. The results indicate that conditioning temperature strongly influences the evolution of tensile behaviour. Specimens thermo-oil-conditioned at 24 °C and −30 °C exhibited a non-monotonic evolution of tensile strength, characterised by an initial reduction after 4 months followed by recovery and an apparent tendency towards stabilisation at longer exposure durations. In contrast, specimens thermo-oil-conditioned at 60 °C exhibited a continuous increase in tensile strength throughout the investigated period. Although elevated testing temperatures reduced the absolute tensile strength, the relative trends associated with thermo-oil conditioning remained observable. The findings indicate that long-term thermo-oil exposure of PA66-GF25 does not necessarily lead to continuous degradation of tensile performance under the investigated conditions. Instead, the material exhibits a transient response at intermediate exposure durations followed by recovery or an apparent tendency towards stabilisation of tensile performance. These results provide a long-term experimental tensile dataset for PA66-GF25 under combined thermal and lubricant exposure conditions and highlight the importance of extended conditioning when evaluating material performance for lubricated engineering applications. The findings show that intermediate exposure data may not be sufficient for assessing long-term tensile behaviour. However, the mechanisms responsible for the observed tensile strength evolution require further verification using complementary physicochemical and microstructural analyses. Full article

Growing environmental concerns associated with Portland cement production, along with the continuous accumulation of construction and demolition waste, have intensified the need for sustainable construction materials and effective recycling strategies. This study experimentally investigates the performance of fly ash-based geopolymer concrete (GPC) incorporating recycled concrete aggregate (RCA) as a partial replacement for natural coarse aggregate, compared to conventional ordinary Portland cement concrete (OPC), with a particular focus on integrated durability performance. Ten mixtures were prepared, including five GPC and five OPC mixes with RCA replacement levels of 0–100% by volume. Mechanical properties were evaluated through compressive, splitting tensile, and flexural strength tests, while durability performance was assessed using water permeability, chloride penetration, acid resistance, elevated temperature exposure up to 1000 °C, and accelerated corrosion tests, supported by SEM–EDX analysis. Results show that GPC outperforms OPC across all replacement levels. Optimal performance was achieved at 20–40% RCA, while at 60% RCA a slight reduction in strength was observed; however, the values remained relatively high, particularly for GPC mixtures, indicating stable performance. A significant reduction occurred only at full replacement. GPC also exhibited lower permeability, enhanced corrosion resistance, improved thermal stability, and better resistance to acid attack. This study provides strong evidence that GPC can effectively compensate for the inherent limitations of RCA, offering a durable and eco-efficient alternative for structural and infrastructure applications. Full article

The growing demand for sustainable materials has renewed interest in replacing conventional petroleum-based wood adhesives with natural, environmentally friendly alternatives. This study evaluated the bonding performance of a conventional polyvinyl acetate (PVAc) adhesive and three natural adhesives—bone glue, fish glue and casein—for bonding European beech (Fagus sylvatica L.) wood of Greek origin. Bond quality was assessed according to ISO 6238:2018 by measuring shear strength and wood failure under ambient laboratory conditions (23 ± 2 °C) and after exposure to 50 °C for 15 days, simulating elevated temperatures that may occur in indoor environments. PVAc exhibited the most consistent bonding performance, whereas casein achieved shear strength comparable to that of PVAc, demonstrating its potential as a sustainable alternative for interior wood bonding. In contrast, bone glue and fish glue exhibited lower shear strength, greater variability in bond performance, and practical limitations associated with their shorter working and setting times. The percentage of wood failure generally followed the same trend as shear strength, confirming the relationship between bond quality and adhesive performance. Moderate thermal exposure did not significantly affect shear strength but resulted in lower wood failure percentages for the natural adhesives, whereas PVAc maintained, and slightly improved, its bond strength after thermal exposure. These findings demonstrate the promising performance of casein as a natural wood adhesive while highlighting the influence of moderate thermal exposure on the durability of natural adhesive systems intended for indoor applications. Full article

As timber construction continues to expand toward taller and larger buildings, ensuring structural resilience under fire conditions requires advanced fire–structural performance assessment approaches. Such assessments generally integrate fire models to define thermal exposure, heat transfer models to predict temperature evolution within structural members, and structural models to evaluate fire-induced structural response. While substantial progress has been achieved in fire and thermal modelling, the structural modelling component, particularly constitutive representation of timber behaviour at elevated temperatures, remains comparatively less developed. This paper presents Wood^ST, a temperature-dependent plastic–damage constitutive modelling approach developed to advance the structural assessment of timber structures under fire conditions. The key modelling components of Wood^ST are briefly introduced, and its capabilities are demonstrated through applications to representative timber structural systems, including bending members (LVL, glulam w/o openings, OSB-web I-joists), axially loaded compression members considering stability effects, complex bolted timber connections and assemblies (light wood frame and hybrid timber–concrete floors) involving multiple interacting components and contact behaviour. The presented applications demonstrate the capability of Wood^ST to capture fire-induced material degradation, nonlinear response, instability, and structural interaction across multiple scales. These advances support performance-based fire design and contribute to the development and implementation of design codes and standards (e.g., CSA O86 and ISO TC92), while facilitating innovation in timber products and structural systems. Full article

This article is a continuation of research conducted by the authors on the effects of fire on cementitious composites and presents findings of an investigation into cement mortars that incorporate monofilament (I) and multifilament (F) polypropylene fibres following exposure to temperatures between 100 and 600 °C. Research was undertaken to examine the effect of adding fibre on the mechanical performance, microstructural characteristics, and thermochemical degradation behaviour of the mortars under conditions representative of high-temperature exposure during fires in energy infrastructure facilities. The scope of the research comprises establishing the modulus of elasticity using dog-bone-shaped specimens, as well as flexural and compressive strength tests performed on prisms measuring 4 × 4 × 16 cm and on 10 × 10 × 10 cm cubes to determine the strength class of the mortars. Microstructural analyses complemented the mechanical testing, performed with the use of scanning electron microscopy (SEM); this made it possible to assess temperature-induced changes in the cement matrix. The results have demonstrated that polypropylene fibres had a significant influence on the degradation behaviour of mortars subjected to elevated temperatures, particularly those between 200 and 400 °C, where fibre melting promoted the formation of additional pore channels. This phenomenon promotes the dissipation of internal energy associated with boiling water vapour contained in the capillary pores, as well as water released during the dehydration of cement hydration products, thereby limiting rapid pressure build-up and reducing the risk of explosive spalling. Moreover, the observed microstructural changes were associated with progressive decomposition of C–S–H gels and other thermo-chemical processes occurring within the cement matrix. The results confirm that polypropylene fibres act as a passive mechanism for the dissipation of thermal and mechanical energy in cement mortars, which has a positive effect on their performance under high-temperature conditions. The study provides new experimental data of significance for the design of cement-based materials with enhanced resistance to thermal exposure in energy-sector facilities. Full article

Potassium silicate is used as an inorganic fire-retardant treatment for wood, but its effect on the short-term thermal response of different species under combined temperature–moisture conditions remains insufficiently described. This study investigated spruce (Picea abies (L.) H. Karst) and beech (Fagus sylvatica L.) wood impregnated with potassium silicate and exposed to temperatures representing drying, mild thermal loading and the onset of thermal degradation. The evaluation included impregnation uptake, moisture content, mass changes, heat-transfer behavior, differential scanning calorimetry (DSC), chemical composition, Fourier-transform infrared spectroscopy (FTIR) of isolated cellulose and color measurements. Spruce showed higher uptake than beech, with an average weight percentage gain (WPG) of 10.5% compared with 3.6%. The treatment increased equilibrium moisture content by 2.6 percentage points in spruce and 1.1 percentage points in beech. Heat-transfer measurements showed that temperature and moisture governed heating: higher target temperatures were reached faster, whereas air-conditioned samples heated more slowly due to water evaporation. At lower temperatures, the direct effect of impregnation on heating time was limited, whereas at higher temperatures the treatment more clearly affected the subsequent degradation response. DSC revealed lower thermal resistance of beech and increased endothermic heat absorption in impregnated samples, particularly spruce. Higher-temperature exposure caused mass loss, hemicellulose degradation, moderate cellulose structure modification and visible color changes, with ΔE* exceeding 52 in impregnated spruce after 210 °C. The elevated-temperature response was governed by wood species, uptake, moisture content and thermal exposure level. Full article

In this study, brick plant waste was used to produce alkali-activated mortars. Four mixtures with identical compositions but different mixing sequences and curing methods were prepared. Two were conventionally produced using a pre-cooled 10 M potassium hydroxide (KOH) solution and sodium silicate (Na₂SiO₃), with one cured at ambient conditions and the other at an elevated temperature. The remaining two used modified mixing sequences to utilize internally generated heat for curing (direct KOH powder addition and addition of KOH dissolved in water immediately before mixing). The influence of mixing sequence and curing method on mechanical properties and high-temperature performance was evaluated after exposure to 600 °C through residual flexural and compressive strengths, mass loss, and visual examination of specimen cross-sections. The two best-performing mortars were further characterized by Fourier-transform infrared spectroscopy (FT-IR) and field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (FE-SEM-EDS), while the mixture combining favorable high-temperature performance with simple preparation was additionally analyzed for thermal conductivity and specific heat capacity. The conventionally prepared, elevated-temperature-cured mixture exhibited the lowest room-temperature flexural and compressive strengths (2.7 and 12.9 MPa, respectively) but the best high-temperature performance, with flexural and compressive strength increases of 14.8% and 10.9%, respectively, after exposure to high temperature. Visual assessment may suggest some degree of structural densification in this mixture and in the mixture prepared by direct addition of KOH powder to the dry components, whereas the other two mixtures may exhibit signs of partial weakening in the interfacial transition zone (ITZ). Among the internally cured mixtures, direct KOH powder addition produced slightly better room- and high-temperature performance than adding KOH dissolved in water immediately before mixing. FT-IR and FE-SEM-EDS confirmed the formation of potassium and sodium aluminosilicate hydrate, (K,N)-A-S-H, gel in the conventionally prepared, elevated-temperature-cured mixture and the mixture with direct KOH powder addition. The nearly unchanged compressive strength of the KOH-powder-based mixture was associated with a high retention of thermal conductivity (93%) and specific heat capacity (80%) after high-temperature exposure. Full article

Liquid water in hydrogels exhibits an adsorption-desorption dynamic equilibrium with the surrounding environment, which leads to the instability of mechanical properties. To address this limitation, we propose an innovative design of conductive composite organogels by incorporating compatible linear lauryl alcohol (LA) and multi-walled carbon nanotubes (CNTs) into a poly(butyl methacrylate) (PBMA) network. Carbon chains of LAform physical crosslinks with PBMA side chains, effectively replacing inherent polymer chain entanglements. This structural innovation facilitates rapid chain rotation and sliding during stretching, so that the gel has a super stretching property of up to 2460%. At elevated temperatures, weakened interactions between LA–PBMA and PBMA–PBMA chains reduce physical confinement of CNTs within the PBMA network. Simultaneously applying a directional electric field, CNTs undergo rotation and translation to reconstruct an optimized conductive pathway, granting the composite distinctive temperature-sensitive electrical conductivity. Critically, all components in the PBMA/LA/CNTs (PLCs) exhibit low volatility and hydrophobicity. These characteristics enable the organogel to retain excellent flexibility and stable electrical performance after prolonged immersion in deionized water, exposure to vacuum, and even under extreme conditions at 120 °C. Such comprehensive stability suggests promising applications in deep-sea exploration and aerospace engineering. Full article

Climate change and increasing instability in coastal marine environments have intensified stressors such as elevated temperature, hypoxia, salinity variation, and pollutant exposure, posing major challenges to the survival, health, and culture performance of bivalves. As economically important aquaculture species and key components of coastal ecosystems, bivalves are highly sensitive to environmental fluctuations, making their metabolic responses highly relevant to both physiological adaptation and aquaculture sustainability. Increasing evidence indicates that metabolic remodeling is an important adaptive strategy supporting bivalve tolerance to environmental stress, with amino acid metabolic remodeling emerging as one of its most sensitive and functionally important components. This review summarizes the major response patterns, key pathways, and potential regulatory mechanisms of amino acid metabolism in bivalves under different stress conditions. Different environmental stressors induce distinct yet integrated shifts in amino acid metabolism, including enhanced catabolism, carbon–nitrogen redistribution, osmotic regulation, and antioxidant defense, thereby supporting energy homeostasis and physiological stress tolerance in bivalves. By highlighting amino acid metabolic remodeling as a central mechanism of bivalve adaptation to environmental stress, this review provides insights into adaptive responses, metabolite-based indicators for monitoring aquaculture environments and bivalve health, and management strategies for improving resilience in bivalve aquaculture. Full article