Search Results (4,408)

Gold, as a critical material with both financial and industrial value, is widely used across numerous fields such as finance, aerospace and medical care. Under the global background of increasing geopolitical risks and the advancement of high-tech industries, the demand for gold continues to grow steadily. The main raw materials for extracting gold are mainly divided into ore and electronic waste. Currently, conventional cyanidation remains the dominant industrial method for gold recovery. However, issues such as pollution and high toxicity of cyanide tailings are driving global efforts to explore environmentally friendly alternatives. Therefore, the development of green and efficient gold extraction technology has become a global research hotspot. This article focuses on cyanide-free leaching technologies, providing a detailed review of their current developments, advantages, and limitations, and proposing future trends in gold extraction. The future development directions of gold extraction include the development of thiosulfate–glycine leaching systems, the combination of multi-technology collaborative processes such as ultrasonic assistance and biological treatment to enhance efficiency, the strengthening of microbial metallurgy technology, and the construction of a resource recycling system for electronic waste. This review provides new insights and development directions for extracting gold for sustainable development. Full article

Current challenges in the construction field emphasize the need for compatible and durable materials for heritage interventions. Traditional lime-based mortars often exhibit limitations under environmental exposure, particularly in terms of water absorption and freeze–thaw resistance. This article investigates the performance of hydroxyapatite (HAp)-modified lime mortars applied in a real-scale heritage context, namely a student built micro-museum developed within the Apoș Architecture Summer School. Following the premature degradation of a conventional lime mortar layer applied at roof level, HAp-modified formulations were introduced as a protective and consolidating solution. The experimental approach combines laboratory testing and in situ evaluation, including compressive strength measurements, water absorption, capillarity tests, chromatic analysis, and freeze–thaw assessment. The results indicate a reduction in water absorption from approximately 22% to 12%, an increase in compressive strength from 6.57 MPa to 19.95 MPa and a significant improvement in freeze–thaw resistance, reflected by a decrease in gelivity from 61.2% to 5.73%, compared to traditional lime mortars. In addition, the contact angle increased from 36° to 82°, indicating enhanced hydrophobic behavior. These improvements are associated with pore structure refinement, reduced capillary uptake, and enhanced interfacial bonding within the mortar matrix. The study also highlights the role of real-scale educational environments in validating sustainable material solutions. Full article

Retrofit strategies to improve the energy performance of buildings have gained significant importance worldwide; however, asbestos in older residential buildings is considered a serious threat to both human health and the environment. Existing studies have generally focused on the health effects of asbestos, the properties of insulation materials, or individual aspects of energy performance, while a coherent and comparative conceptual framework for sustainable retrofit systems is limited. This review aims to systematically integrate the current scientific evidence on asbestos management, alternative insulation materials, life cycle assessment (LCA), and circular economy principles to present a literature-informed conceptual decision-support framework for sustainable retrofit. The study used the PRISMA-based literature selection approach, while the evidence from different peer-reviewed studies was comparatively organized in the context of process workflows, risk considerations, lifecycle impacts, and building-physics-related findings. The literature-based results indicate that incorporating safe asbestos management, low-carbon insulation materials, and circular retrofit strategies into an integrated approach can improve energy efficiency and environmental sustainability. However, this study is not based on a validated numerical simulation, an executed optimization model, or calibrated engineering analysis, but rather on a comparative synthesis and conceptual interpretation of the existing literature and presents a decision-support framework that can guide future low-carbon and safe construction strategies. Full article

This study aims to explore the effect of using three distinct silicate- and aluminate-rich rock powders—granodiorite (GDP), alkali-feldspar granite (AFGP), and mafic metavolcanic (MMVP)—sourced from Egypt’s largely unexploited Eastern Desert geological resources, as supplementary cementitious materials (SCMs) in concrete production. Rock samples were processed into ultrafine powders (1.4–1.5 μm average particle size) and utilized as partial cement replacements at 3%, 6%, 9%, and 12% by weight. These rock powders were confirmed to meet ASTM C618 requirements for natural pozzolans, qualifying them as viable SCMs. Pozzolanic activity was confirmed through Strength Activity Index (SAI) testing, with values of 79%, 82%, and 76% for GDP, AFGP, and MMVP, respectively, all exceeding the 75% minimum threshold required by ASTM C618. Fresh concrete workability decreased progressively with increasing rock powder content. Mechanical testing demonstrated optimal replacement levels of 9% for GDP and AFGP, and 6% for MMVP, achieving 28-day compressive strength improvements of 14.1%, 16.0%, and 14.9%, respectively, compared to plain Portland cement concrete without any rock powder replacement (control mix). Splitting tensile strength increased by 14.7%, 12.7%, and 16.3% at optimal dosages. Microstructural analysis via SEM revealed enhanced matrix densification and reduced porosity through physical filler effects and pozzolanic reactions. Energy-dispersive X-ray spectroscopy (EDX) confirmed reduced Ca/Si ratios, indicating enhanced calcium silicate hydrate (C-S-H) gel formation with superior binding characteristics. Results demonstrate that these previously unexploited rock powders effectively function as sustainable SCMs, reducing cement consumption by up to 12%, offering significant environmental benefits through reduced CO₂ emissions and efficient utilization of natural geological resources in sustainable construction practices. Full article

This research investigates the formation and behavior of sustainable crumb rubber-modified gypsum–cement–pozzolan (GCP) composites, with a view to their use in a broad concept for construction. GCP binders are gaining attention as a low-carbon replacement for Portland cement, and the addition of recycled rubber helps the achievement of circular economy goals and potentially increases durability. The present research evaluates the impact of crumb rubber (CR) on the mechanical strength, water absorption, dimensional stability, and freeze–thaw resistance of 3D-printed GCP-rubber composites. Composite blends of variable proportions of crumb rubber were prepared at constant binder ratios. Mechanical properties were defined by prism specimens (40 × 40 × 160 mm) by the flexural and compressive strengths, and deformation was determined by micrometers to measure longitudinal strain as a function of curing. Water absorption was determined prior to freeze–thaw cycling to define pore saturation. Durability was investigated using two approaches: (1) controlled freeze–thaw experiments on cube specimens, with XF1 grade performance achieved, and (2) ultrasonic pulse velocity (UPV) testing of specimens 3D-printed for assessing internal structural change after long-term frost exposure. Results showed that compressive strength decreased moderately (10–20%) with increasing rubber content from 17% up to 50%, while flexural strength improved up to 15%, showing the elastomeric action of CR. Water absorption was reduced by 5–8% in the rubber-modified blends due to the hydrophobic character of rubber. Deformation tests also confirmed minimum length variation (<0.02%) during curing. Freeze–thaw durability was enormously improved, and test specimens retained more than 95% of initial strength. UPV measurements detected only a relatively modest velocity drop (~50 m/s) after 36 days cycling with subsequent stabilization up to 200 days, demonstrating long-term internal structure with minimal progressive damage. In summary, the findings demonstrate that GCP composites with crumb rubber incorporated are printable, dimensionally stable, and capable of freeze–thaw degradation resistance. Despite a moderate loss of compressive strength, the balance of introduced durability and sustainability suggests their competence as viable materials for additive manufacturing in construction. Full article

Research traditionally examines the spatial distribution of urban parks through the lens of spatial equity, overlooking the intricate interaction between the physical foundation of park construction and historical processes. Grounded in the theory of material geography, we investigate the mechanisms underlying the spatio-temporal evolution of urban parks in Shenzhen. We conduct topographical analysis and examine relevant historical policy texts to explore the ‘production of nature’ in China’s post-Mao urbanisation. We find that the distribution of urban parks in Shenzhen is not merely a result of social choice but a product of the interplay between material natural endowments—centred on topography—and urban spatial policies across historical stages. During rapid urbanisation, government-led spatial policies functionally reorganised and assigned symbolic meanings to diverse topographical features, such as plains, hills, and coastal areas, transforming them into urban parks that support capital accumulation and urban upgrading. The proposed ‘topography–policy’ synergistic framework transcends neutral spatial descriptions, revealing the nexus between the commodification of nature and urban governance. We clarify the rationale for the creation of contemporary urban green spaces in China and offer novel theoretical and empirical insights into sustainable urban transformation worldwide. Full article

Traditional wooden granaries in rural Türkiye are disappearing at an accelerating rate due to agricultural abandonment, rural depopulation, and the absence of systematic documentation and conservation frameworks. In the Sındırgı district of Balıkesir, one of the richest concentrations of vernacular granary architecture in the Marmara Region, these structures remain largely unprotected and unstudied within a sustainable design framework, constituting an urgent conservation challenge. This study aims to assess the current preservation status of Sındırgı granaries, classify their typological diversity, and evaluate their sustainability performance against a defined set of ecological design criteria. A mixed methods approach was employed, combining a systematic literature review with extensive fieldwork across 33 neighborhoods. In total, 1411 granaries were identified and grouped into five typologies: evli, Simav, kabak, sandık, and üstü örtülü sandık. These typologies were systematically compared to five parameters: spatial distribution across neighborhoods, plan and section geometry, construction system and structural elements, material selection and condition, and preservation status. This comparison revealed that typological variation is not incidental but directly reflects differences in land ownership, agricultural production capacity, topography, and distance from the district center. Representative examples from each typology were documented through onsite measurements, photogrammetry, technical drawings, and interviews with local craftsmen. The sustainability performance of the granaries was then assessed across seven ecological design criteria: spatial organization, building form design, structural element design, material use and conservation, design with nature, urban design area planning, and nature interaction. The findings demonstrate that the long-term durability of these structures depends on an interrelated system of climate-responsive design decisions rather than any single factor. The study concludes by proposing a holistic conservation model comprising typology-based inventory, roof water moisture-focused intervention, periodic monitoring, and transmission of vernacular building knowledge, a framework applicable to comparable rural granary heritage across the region. Full article

The construction sector must simultaneously meet rising global demand and cut embodied carbon deeply enough to satisfy European Green Deal and Bioeconomy Strategy targets—two pressures that conventional petrochemical-derived materials are poorly placed to resolve. Bio-based alternatives offer a credible path: they sequester carbon, carry lower embodied emissions, improve indoor air quality, and fit naturally within circular economy models. Yet they remain marginal in specification practice. This paper reviews the evidence on bio-based construction materials and maps the barriers that keep them there. The analysis organises these barriers into four levels—structural, economic, technical, and enabling—and traces the conditional relationships between them, with direct consequences for how policy interventions should be sequenced. The strategic case for this transition extends beyond environmental policy: the 2026 Strait of Hormuz disruption is used here as a scenario to show how dependent European construction is on fossil-derived material inputs, and how exposed that dependence leaves the sector to geopolitical supply shocks. The principal obstacles to adoption prove to be institutional and economic rather than technical—regulatory fragmentation, absent harmonised standards, fragile supply chains, and market structures that systematically undervalue bio-based solutions. The paper concludes that meaningful scaling requires coordinated action across governance, market design, and industrial policy, and that material and performance advances alone will not deliver it. Full article

Three-dimensional (3D) bioprinting has rapidly evolved into a controlling platform for the fabrication of patient-specific biomedical implants, with growing importance in advanced drug delivery systems. Beyond structural tissue engineering, bioprinted constructs now function as programmable therapeutic depots capable of localized, sustained, and stimuli-responsive drug release. This review focuses on recent biomaterial design strategies that enable precise control over drug encapsulation, retention, and release kinetics within 3D bioprinted architectures. The physicochemical and mechanical properties of bioinks, including crosslinking density, porosity, degradation behavior, viscoelasticity, and swelling characteristics, directly influence drug loading efficiency and release dynamics under physiological conditions. The rational tuning of these parameters allows the development of constructs that provide spatially controlled and temporally regulated therapeutic delivery. Recent advances in predictive modeling, such as finite element modeling (FEM), data-driven machine learning approaches, and ML, have significantly improved the ability to correlate material composition, printing parameters, and structural geometry with drug diffusion and degradation-mediated release mechanisms. These tools facilitate the optimization of printing variables including extrusion pressure, nozzle diameter, and layer resolution to ensure structural fidelity while maintaining therapeutic functionality. Emerging strategies incorporating multi-material printing, gradient architectures, and stimuli-responsive biomaterials have expanded the potential of 3D bioprinting for combination therapies and personalized medicine. This review discusses key challenges in translating bioprinted drug delivery systems into clinical applications, including the standardization of drug release characterization methods, and long-term stability assessment. Full article

Wood-based panels such as oriented strand board (OSB) have gained increasing relevance in sustainable construction due to their favorable mechanical performance and efficient use of raw materials. This study evaluates the physical and mechanical properties of OSB panels manufactured from residues of five Brazilian tropical species, namely Cambará (Erisma sp.), Caixeta (Simarouba sp.), Cedroarana (Cedrelinga catenaeformis), Tatajuba (Bagassa guianensis), and Tauari (Couratari oblongifolia) bonded with castor oil-based polyurethane resin (12% by dry weight; 3-layer ratio 20:60:20). Seven formulations were tested (five monospecies; two mixed species) and characterized in accordance with EN 300, EN 310, EN 317, EN 319, EN 322, EN 323, ABNT NBR 14810-2, and ASTM D2719. Panel densities ranged from 0.685 to 0.813 g/cm³. Cedroarana and Caixeta panels achieved the highest mechanical performance: MOR of 44.04 MPa and 40.96 MPa, and MOE of 6741 MPa and 6287 MPa, respectively (parallel direction), both exceeding EN 300 OSB/4 thresholds. All panels met internal bond requirements (≥0.5 MPa). Compaction ratio emerged as the primary determinant of mechanical behavior. Mixed species panels performed comparably to monospecies configurations, confirming the viability of residue valorization without species segregation. The castor oil-based resin provided adequate bonding and moisture resistance, supporting its use as a formaldehyde free renewable alternative for structural-grade OSB. Full article

Bamboo, as a rapidly renewable and sustainable material, has gained increasing attention in the construction, furniture, automotive interiors, and packaging industries due to its excellent mechanical properties, light weight, and environmental friendliness. However, the inherent flammability of bamboo, characterized by its porous structure and high hemicellulose content, poses a significant fire hazard that severely limits its wide application. This review systematically synthesizes recent advances in the fire performance and flame-retardant modification of bamboo-based materials. First, the thermal degradation behavior and combustion mechanisms of bamboo are discussed in relation to its primary chemical constituents, including cellulose, hemicellulose, and lignin. Subsequently, various flame-retardant strategies are reviewed, including inorganic flame retardants, phosphorus–nitrogen systems, nanomaterial-based additives, and bio-based flame-retardant approaches. The effectiveness of different modification techniques, such as impregnation treatment, adhesive modification, and surface coating, is also analyzed. Future research directions are proposed, emphasizing the development of environmentally friendly flame-retardant systems, multifunctional modification strategies, and the design of high-performance flame-retardant bamboo-based materials. This review aims to provide a comprehensive framework for advancing the fire safety design and sustainable application of bamboo-based materials. Full article

Stabilizing weak soils is a well-known pavement and geotechnical engineering technique. This technique involves introducing minimal cementitious materials to improve the soil’s geotechnical characteristics. This paper investigates the use of recycled industrial polymer waste (IPW) as a reinforcement material in the presence of cementitious binders to stabilize weak silty sand soil (SM), supporting sustainable engineering practices. The randomly distributed IPW were added as percentages of 0%, 5%, and 10% to a mixture of lime soil and cement soil, with varying amounts of 0% to 6% of lime (L) and 0% to 6% of ordinary Portland cement (OPC), respectively. The laboratory experiments were conducted on natural and stabilized samples in wet (unsoaked) and submerged (soaked) conditions. The experimental program included Proctor compaction, California bearing ratio (CBR), unconfined compressive strength (UCS), durability tests, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction analyses. The resilient modulus (Mr) was estimated using an empirical equation. The outcomes of this experimental study show that adding a combination of IPW shreds with a small amount of L and/or OPC to the SM soil provides a significant increase in the UCS, CBR, durability and Mr values compared with case of SM with only L, which allows for superior characteristics and increases strength and stiffness parameters throughout any phase of earthwork construction design, resulting in stronger and stiffer subgrades. These results were reinforced by microstructural observations from SEM, EDS, and DRX, confirming the formation of cementitious gels and chemical compounds, consistent with the macro-scale mechanical improvements. The expected practical outcomes include potential reductions in pavement thickness, which can help lower pavement stabilization costs and extend its service life. Additionally, the use of waste materials to replace raw materials contributes to decreased energy consumption and emissions, although detailed assessments are needed to quantify these effects. Full article

The construction sector accounts for approximately 36% of global final energy consumption and close to 40% of total CO₂ emissions, making it a primary target of international climate policy. Despite this growing attention, the indigenous building traditions of the Ecuadorian Andes remain virtually absent from the international scientific literature on vernacular sustainability. This study presents a systematic field documentation and bioclimatic assessment of vernacular bahareque dwellings in the Kichwa-Saraguro community of Ilincho, canton of Saraguro, province of Loja, Ecuador (2700 m a.s.l.). A field survey of 30 dwellings identified five morphological typologies—I-1P, I-2P, 2B, L, and C—with typology C, a compact C-shaped block with a three-sided portal, accounting for 53.3% of the sample. A structured multi-criteria framework of 48 bioclimatic indicators distributed across eight categories, adapted to the cold-temperate mountain climate of the study area, was applied to quantify each typology’s bioclimatic performance. All typologies exceeded 75% overall compliance on the global Bioclimatic Performance Index (BPI), with typology C achieving the highest value (88.5%). Categories F (Materials and construction) and H (Cultural and social aspects) scored 100% across all typologies, reflecting system-level properties of the bahareque constructive system rather than morphological differences between typological variants; a supplementary morphological BPI restricted to Categories A–E and G is reported. An exploratory, uncalibrated energy simulation of typology C provided indicative evidence consistent with the expected thermal behavior of a high-thermal-mass bahareque envelope, with simulated minimum temperatures in the sleeping area within the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 55-2013 comfort range (T-min 18.80 °C). Collectively, these findings contribute quantified bioclimatic documentation of vernacular bahareque architecture in Ilincho, identifying attributes—encompassing solar control, spatial compactness, high-thermal-mass envelope performance, and use of locally sourced low-embodied-energy materials—that may inform sustainable rural housing discussions in the Ecuadorian Andes and comparable high-altitude mountain contexts. Its documentation in the indexed scientific literature constitutes a step toward recognizing this constructive heritage as a practical resource for low-carbon building policy. Full article

Concrete remains one of the most extensively utilized construction materials for buildings, bridges, and infrastructure. High-volume fly ash (HVFA) concrete has emerged as a sustainable choice to conventional mixtures, primarily due to its reduced cement demand and enhanced durability. Nevertheless, systematic investigations on the fineness fly ash contributions both for strength growth and durability performance of normal-strength HVFA concrete remain limited. The present study examines the effect of fly ash particle size, employed as a partial cement replacement, on the compressive strength and durability of normal-strength HVFA concrete. In this work, 50% of the cement by weight was substituted with fly ash of two fineness levels: passing sieve No. 200 and sieve No. 400. Twelve specimens were prepared for each mix variation, comprising compressive strength specimens (Ø15 cm × 30 cm) tested at 14, 28, and 56 days, as well as durability specimens assessed using the Rapid Chloride Penetration Test (RCPT) at 56 days. The results demonstrate that finer fly ash markedly improves compressive strength, with the highest value of 36.33 MPa recorded at 56 days for HVFA concrete comprising fly ash passing sieve No. 400. Regarding durability, increased fineness substantially reduced chloride ion ingress, as indicated by a decline in charge passed from 1845 coulombs in normal concrete to 987 coulombs in HVFA concrete with fly ash passing sieve No. 400, corresponding to a classification of very low chloride penetrability. These findings highlight the critical contribution of the fineness of fly ash in optimizing both mechanical performance and durability characteristics of HVFA concrete. Full article

The reliability of engineering structures is essential to ensure safety, durability, and sustainability. In reinforced concrete (RC), shear resistance is one of the most uncertain design aspects due to the natural variability of material properties and construction quality. Conventional design methods defined by Eurocode rely on characteristic values and partial safety factors that may not reflect the actual performance of in situ concrete. This study proposes a probabilistic framework for shear assessment that integrates material variability derived from conformity testing. Statistical parameters, including mean value and coefficients of variation (COV) of compressive strength, are incorporated into comparative reliability analysis using the First-Order Reliability Method (FORM) and Latin Hypercube Sampling (LHS). Parametric analyses are performed to quantify the influence of material variability on the reliability index β and failure probability $P_f$. The effect of varying the coefficient of variation (CoV) of the concrete compressive strength is investigated in the range from 0.01 to 0.2, both under the assumption of statistical independence and with consideration of correlation between selected variables. The sensitivity analysis is carried out to provide clear insight into the influence of uncertainty in the input parameters on the reliability of the considered limit state. The proposed framework provides a more realistic representation of structural safety and supports data-driven, performance-based management of concrete infrastructures. Full article