Search Results (742)

The deterioration of concrete hydraulic structures caused by chemical factors, seepage, and environmental stress necessitates advanced protective coatings that enhance durability, flexibility, and environmental sustainability. Conventional protective systems often exhibit limited durability under combined hydraulic, thermal, and chemical stress. In this study, a novel polyfluorosilicone-based coating system is presented, which integrates a deep-penetrating nano-primer for substrate reinforcement, a crack-bridging polymer intermediate layer for impermeability, and a polyfluorosilicone topcoat providing UV and weather resistance. The multilayer architecture addresses the inherent trade-offs between adhesion, flexibility, and durability observed in conventional waterproofing systems. Informed by a mechanistic study of interfacial adhesion and failure modes, the coating exhibits outstanding high mechanical and performance characteristics, including a mean pull-off bond strength of 4.56 ± 0.14 MPa for the fully cured triple-layer coating system, with cohesive failure occurring within the concrete substrate, signifying a bond stronger than the material it protects. The system withstood 2.2 MPa water pressure and 200 freeze–thaw cycles with 87.2% modulus retention, demonstrating stable mechanical and environmental durability. The coating demonstrated excellent resilience, showing no evidence of degradation after 1000 h of UV aging, 200 freeze–thaw cycles, and exposure to alkaline solutions. This water-based formulation meets green-material standards, with low volatile organic compound (VOC) levels and minimal harmful chemicals. The results validate that a multi-scale, layered design strategy effectively decouples and addresses the distinct failure mechanisms in hydraulic environments, providing a robust and sustainable solution. Full article

Geopolymers are a new breed of construction materials that are environmentally friendly and replace old Portland cement. These materials are produced through the alkaline activation of industrial and agricultural waste rich in aluminosilicates. The growing interest in sustainable building solutions has driven research into their development. Palm oil fuel ash (POFA) and waste ceramic tile powder (WTCP) are both highly rich in reactive aluminosilicates and widely recommended for the production of sustainable geopolymers. This study aims to evaluate the suitability of POFA and WTCP as sustainable alternatives to conventional binders and to identify the potential advantages of each waste material in developing eco-friendly, high-performance geopolymers. The results indicate that specimens prepared with a high content (50 wt%) of POFA or WTCP, incorporating fly ash and slag, can achieve compressive strengths of up to 50 MPa after 28 days of curing. However, increasing the proportion of POFA or WTCP from 50% to 60% and 70% resulted in a significant reduction in compressive strength. In contrast, specimens containing higher proportions of POFA and WTCP demonstrated superior durability when exposed to aggressive environments. In summary, the findings indicate that WTCP is more suitable than POFA for producing geopolymers as eco-friendly construction materials. Its superior reactivity, workability, early-age strength development, and durability make it a promising precursor for sustainable applications in the construction sector. Full article

Resistance against water penetration is one of the key indicators of concrete durability in humid and pressurized environments. An intelligent model based on the XGBoost machine-learning algorithm was developed to predict the water penetration depth, using 1512 independent experimental measurements. The influential variables included water pressure, pressure duration, thermal cycles, fiber content, curing, and compressive strength. The investigated concrete specimens and field-tested structures in this study were exposed to arid and hot climatic conditions, and the proposed model was developed within this environmental context. To accurately simulate the water transport behavior, a cylindrical-chamber test was employed, enabling non-destructive and in-situ evaluation of structures. Correlation analysis revealed that compressive strength had the strongest negative influence (r = −0.598), while free curing exhibited the strongest positive influence (r = +0.654) on penetration depth. After hyperparameter optimization, the XGBoost model achieved the best performance (R² = 0.956, RMSE = 1.08 mm, MAE = 0.81 mm). Feature importance analysis indicated that penetration volume, pressure, and curing were the most significant predictors. According to the partial dependence analysis, both pressure and duration exhibited an approximately linear increase in penetration depth, while a W/C ratio below 0.45 and curing markedly reduced permeability. Microstructural interpretation using MIP, XRD, and SEM tests supported the physical interpretation of the trends identified by the machine-learning model. The results demonstrate that machine-learning-models can serve as fast and accurate tools for assessing durability and predicting permeability under severe environmental conditions. Finally, the permeability of several real structures was evaluated using the machine-learning approach, showing excellent prediction accuracy. Full article

The invention concerns a screw-driven shredder for solid photopolymer resin, designed for both terrestrial use and prospective deployment in microgravity environments. The system addresses the need for efficient recycling of cured photopolymer waste generated by stereolithography (SLA) 3D printing—a process not yet implemented in orbit, but envisioned as part of future closed-loop additive manufacturing systems aboard space stations or lunar habitats. The proposed device is a compact, hermetically sealed mechanical unit composed of ten subassemblies, featuring two counter-rotating screw shafts equipped with carbide milling inserts arranged helically to achieve uniform and controlled fragmentation of solid SLA residues. The shredding process is supported by a pressurized inert fluid circuit, utilizing carbon dioxide (CO₂) as a cryogenic working medium to enhance cutting efficiency, reduce heat accumulation, and ensure particle evacuation under microgravity conditions. Studies indicate that CO₂-assisted cooling can reduce tool-tip temperature by 10–30 °C, cutting forces by 5–15%, and electrical power consumption by 5–12% while extending tool life by up to 50%. This invention thus provides a key component for a future in situ photopolymer recycling loop in space while also offering a high-efficiency shredding solution for Earth-based photopolymer waste management in additive manufacturing. Full article

The article studies the influence of chlorosulfonated polyethylene CSM 40 as a compatibilizer on the curing characteristics of the rubber compound, dynamic mechanical analysis, morphology, physico-mechanical and performance properties of vulcanized rubber based on a compound of ethylene propylene diene monomer EPDM S 501A and nitrile butadiene NBR 2645 rubbers. DMA studies indicate that the temperature dependence of tanδ for vulcanizates with and without a compatibilizer based on EPDM S 501A/NBR 2645 at a ratio of 75/25 parts per hundred parts of rubber (phr) has a bimodal character, which indicates the incompatibility of the rubber phases. The temperature dependence for EPDM S 501A/NBR 2645 vulcanizates (25/75 phr) with and without a compatibilizer has a monomodal form, which characterizes the improved compatibility of the rubber phases. SEM showed that a clearly defined microporous structure is observed on a cleavage of vulcanizate sample EPDM/NBR (25/75 phr) without a compatibilizer; with the addition of CSM 40, this feature is retained, but becomes less pronounced. It is shown that vulcanizates containing the compatibilizer CSM 40 are characterized by increased strength properties and hardness compared to vulcanized rubber without a compatibilizer. It was established that the vulcanized rubber based on EPDM S 501A/NBR 2645/CSM 40 (25/75/5 phr) is characterized by the smallest changes in the elastic-strength properties and hardness of vulcanizates after a day of thermo-oxidative aging in air and their weight after exposure to industrial oil I-20A and standard petroleum fluid SZhR-1 at room temperature among vulcanizates based on EPDM S 501A and NBR 2645. The vulcanizate of the rubber compound, including a compound of EPDM/NBR (25/75 phr) with a compatibilizer CSM 40 in an amount of 5 phr (2.88 wt.%), is characterized by stable physico-mechanical properties and improved performance properties. This rubber compound can be used for the manufacture of rubber products operating under the influence of oils and hydrocarbon environments. Full article

Global demand for adaptable and rapidly deployable construction solutions in offshore, coastal, and fluvial environments continues to rise, driven by pressing needs to develop energy platforms, improve coastal resilience, and support emergency response in the face of natural disasters. Increased investment in human-made coastal infrastructure, such as piers, support structures for power lines, offshore wind farms, and seawall protection systems, further underscores this trend. This study investigates the development of printable concrete mixtures for underwater environments using seawater as a replacement for freshwater, using a 3D printing syringe-based extrusion system. The effect of seawater addition and the printing medium (in air vs. underwater) was assessed via rheological and mechanical performance characterization. The results indicate rheological properties are favorable for seawater adoption by producing mixtures with higher yield stress and viscosity with the same levels of admixtures used for freshwater. Seawater-based mixtures demonstrated superior dimensional stability compared to freshwater counterparts, maintaining cross-sectional geometry, while compressive strength results showed no statistical differences between in-air and underwater samples. However, flexural strength was significantly influenced by geometry and printing medium. These findings establish critical rheological parameters for printable underwater mixtures and highlight the need for optimized curing strategies and layer bonding techniques to improve interfacial strength in underwater 3D printing applications. Full article

An alternative conductive ink based on carbon nanotubes (CNTs) was developed using a platinum-catalyzed silicone elastomer and isopropyl alcohol (IPA). The inclusion of IPA in the conductive CNT ink facilitated the optimization of its mechanical strength, electrical conductivity, and viscosity. Compared to conventional silicone rubber-based conductive polymers that often solidify in a few hours at room temperature or with heating, this liquid composite of CNT particles and IPA exhibited a prolonged duration of up to several months in a hermetic environment, maintaining chemical stability even with the elastomer and its curing agent. The gradual evaporation of IPA initiates a well-known cross-linking process, leading to stretchability and electrical conductivity derived from the silicone elastomer and CNT particles, respectively. The relationship between the mechanical strength and electrical conductivity of the hardened conductive CNT ink was studied, which helped determine the optimized concentration of CNT particles in the conductive CNT ink. Subsequently, a piezoresistive sensor was designed, fabricated, and evaluated. The conductive CNT ink-based piezoresistive sensor showed high sensitivity and good repeatability with respect to a wide range of external forces. The effect of the concentration of CNT particles on the viscosity of the conductive CNT ink was also investigated, providing a better understanding of the entanglement of CNT particles within the silicone elastomer. A coating test using the conductive CNT ink with a paper cutting machine demonstrated its potential for adaptation to various printing techniques, including screen printing. The proposed conductive CNT ink, characterized by a simple chemical composition, facile fabrication process, use of non-toxic elements, high electrical conductivity, and stretchability, combined with an extended duration, has the potential to be applied for multiple purposes, such as various types of flexible and wearable electronics. Full article

The disposal of industrial waste poses a significant environmental challenge, often leading to pollution and degradation of surrounding and terrestrial ecosystems. This study investigates the sustainable valorization of such wastes through the development of one-part geopolymer mortars. Solid sodium silicate was employed as a dry alkali activator for binary blends comprising ground granulated blast-furnace slag (GGBS), clay brick powder (CBP), steel slag (SS), and fly ash (FA), with all mixtures cured under ambient conditions. The mortars were evaluated in terms of fresh properties (flow and setting time) and hardened characteristics, including compressive strength, density, water absorption, and porosity. Durability performance was assessed through mass loss, visual degradation, and compressive strength retention following exposure to acidic (H₂SO₄, HCl) and sulfate environments. Microstructural characterization using XRD, SEM, and FTIR provided insight into the mechanisms of gel formation and degradation in aggressive media. The results revealed that incorporating 5% FA into GGBS-based mortars enhanced 28-day compressive strength by 21.7% compared with the control mix. The inclusion of industrial by-products promoted the formation of C–S–H and C–(A)–S–H gels, contributing to a denser and more refined microstructure. Overall, the findings demonstrate that one-part geopolymer mortars offer a promising, eco-efficient, and durable alternative to traditional cementitious systems, while also addressing safety and handling concerns associated with liquid alkaline activators used in conventional two-part geopolymer formulations. Full article

Monitoring the curing process of concrete remains a challenging and critical aspect of modern construction, often hindered by labour-intensive, invasive, and inflexible methods. The primary aim of this study is to develop an integrated IoT-enabled platform for automated, real-time monitoring of concrete curing, using a combination of LoRa-based sensor networks and an LTE-M backhaul. The resulting ConMonity system employs embedded multi-sensor nodes—capable of measuring strain, temperature, and humidity–connected via an energy-efficient, TDMA-based LoRa wireless protocol to an LTE-M gateway with cloud-based management and analytics. By employing a robust architecture with battery-powered embedded nodes and adaptive firmware, ConMonity enables multi-modal, multi-site assessments and demonstrates stable, autonomous operation over multi-modal, multi-site assessment and demonstrates stable, autonomous operation over multi-month field deployments. Measured data are transmitted in a compact binary MQTT format, optimising cellular bandwidth and allowing secure, remote access via a dedicated mobile application. Operation in laboratory construction environments indicates that ConMonity outperforms conventional and earlier wireless monitoring systems in scalability and automation, delivering actionable real-time data and proactive alerts. The platform establishes a foundation for intelligent, scalable, and cost-effective monitoring of concrete curing, with future work focused on extending sensor modalities and enhancing resilience under diverse site conditions. Full article

In response to the requirements of wellbore plugging and lost circulation control, this study designed and prepared a new type of thixotropic polymer gel system. The optimal formula was obtained through systematic screening of the types and concentrations of high molecular polymers, cross-linking agents, flow pattern regulators, and resin curing agents. Comprehensive characterization of the gel’s gelling performance, thixotropic properties, high-temperature stability, shear resistance, and plugging capacity was conducted using methods such as the Sydansk bottle test, rheological testing, high-temperature aging experiments, plugging performance evaluation, as well as infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis, and its mechanism of action was revealed. The results show that the optimal formula is 1.2% AM-AA-AMPS terpolymer + 0.5% hydroquinone + 0.6% S-Trioxane + 0.8% modified montmorillonite + 14% modified phenolic resin. This gel system has a gelling time of 6 h, a gel strength reaching grade H, and a storage modulus of 62 Pa. It exhibits significant shear thinning characteristics in the shear rate range of 0.1~1000 s⁻¹, with a viscosity recovery rate of 97.7% and a thixotropic recovery rate of 90% after shearing. It forms a complete gel at a high temperature of 160 °C, with a dehydration rate of only 8.5% and a storage modulus retention rate of 80% after aging at 140 °C for 7 days. Under water flooding conditions at 120 °C, the converted pressure-bearing capacity per 100 m reaches 24.0 MPa. Mechanism analysis confirms that the system forms a stable composite network through the synergistic effect of “covalent cross-linking—hydrogen bonding—physical adsorption”, providing a high-performance material solution for wellbore plugging in high-temperature and high-salt environments. Full article

This paper examined the effect of marble powder (MP) on air-cured cement-based materials when subjected to sulfuric acid (H₂SO₄) attack. Four MP replacement levels were tested: 0%, 5%, 10%, and 15% by weight of cement. The prepared samples were cured for 90 days prior to being exposed to H₂SO₄. Macroscopic tests for apparent density and compressive strength along with microstructural characterization using X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed to determine the effect of MP on the properties of the materials. The Rietveld method was used to analyze the amounts of different crystalline phases and amorphous calcium silicate hydrate (C-S-H). The obtained results indicate that 5% MP in air-cured cement -based materials exhibited the best behavior with acceptable resistance to acid attacks. This level of MP replacement was found to optimize the filler effect, improve the hydration process, and enhance the matrix density, which in turn reduces the permeability of the material and increases acid resistance. This is attributed to the balanced contribution of MP to phase formation, particularly calcite, which helps to counteract acid-induced dissolution, while also preserving the stability of C-S-H phases. This study provides a new perspective of the role of MP in influencing phase content (crystalline and amorphous phases) and their possible impacts on macroscopic properties such as apparent density and compressive strength. MP behaved as a filler, to improve hydration and resistance to acid attacks. Additionally, using MP as a replacement for ordinary Portland cement (OPC) offers a sustainable alternative by reducing waste and promoting the recycling of marble industry by-products, thereby contributing to environmental sustainability. It is recommended that, 5% MP is the optimal replacement content to enhance durability and mechanical properties in air-cured cement-based materials in aggressive environments, as it is both practical and achievable for infrastructure to be subjected to the aggressive environment. Full article

The built environment (BE) encompasses an enormous volume and substantial material mass. However, structures within it typically serve single, limited functions. Enhancing these structures with multifunctional capabilities holds significant potential for achieving broader sustainability goals and creating impactful environmental benefits. Among these potential multifunctional applications, carbon capture, reduction, and storage are especially critical, given the current built environment’s substantial contribution of approximately 40% of global energy and CO₂ emissions. Keeping this potential in view, this comprehensive review critically evaluates carbon management strategies for the built environment via three interrelated approaches: carbon capture (via photosynthesis, passive concrete carbonation, and microbial biomineralization), carbon storage (employing carbonation curing, mineral carbonation, and valorization of construction and demolition waste), and carbon reduction (integrating industrial waste, alternative binders, and bio-based materials). The review also evaluates the potential of novel direct air-capture materials, assessing their feasibility for integration into construction processes and existing infrastructure. Key findings highlight significant advancements, quantify CO₂ absorption potentials across various construction materials, and reveal critical knowledge gaps, thereby providing a strategic roadmap for future research direction toward a low-carbon, climate-resilient built environment. Full article

Human life expectancy has risen dramatically in the last century, but this demographic triumph has come at the cost of an explosion of non-communicable diseases (NCDs), threatening the sustainability of healthcare systems in aging, low-fertility societies. Evolutionary medicine provides a framework to understand, at least in part, this paradox. Many vulnerabilities to disease are not failures of design but the predictable outcomes of evolutionary trade-offs, constraints, and mismatches. Evolutionary mismatch theory explains how traits once advantageous in ancestral environments become maladaptive in modern contexts of abundance, sedentarism, and urbanization. The developmental origins of health and disease (DOHaD) concept describes how epigenetic plasticity in early life can buffer or amplify these mismatches, depending on whether adult environments align with developmental forecasts. Transgenerational epigenetic inheritance, even if still debated in humans, may further influence phenotypic plasticity, increasing or mitigating the mismatch. In evolutionary terms, the theories of mutation accumulation, antagonistic pleiotropy, and the disposable soma explain why longer lifespans, and ecological and social conditions profoundly different from those in which we developed, increase the likelihood that these costs are expressed clinically. Because most NCDs can be prevented and effectively controlled but not cured, efforts should prioritize quality of life for people, families, and communities. At the individual level, aligning lifestyles with evolved biology can mitigate risk, but the greatest leverage lies in population-level interventions. Urban health strategies represent a forward-looking attempt to realign modern environments with human biology. In this way, the concept of the evolutionary misfit becomes not just a diagnosis of maladaptation, but a guide for building healthier, more sustainable societies. Full article

This study presents the effects of using pyrite aggregate in field concretes on the mechanical, surface performance, and algal growth tendency of concrete. The substitution of pyrite influences the process of hydration, as the gradual release of its iron- and sulfur-bearing components shifts the reaction mechanism, leading to differences in phase formation and some modification in the pore structure of the cement matrix. Three different concrete mixes (PB0, PB2.5%, and PB7.5%) were designed by replacing 0%, 2.5%, and 7.5% of the total weight of sand and crushed sand with ground pyrite as a fine aggregate. Prismatic specimens of 80 × 100 × 200 mm were produced from these mixtures and mechanical properties such as flexural, splitting tensile, and abrasion were investigated after 28 days of curing. Then, to determine the effect of pyrite on concrete surface properties, pyrite was substituted on the surface of three concrete specimens produced in 50 × 240 × 500 mm dimensions at rates of 0, 1, and 3 kg/m². These specimens were divided into two groups: one group was exposed to clean water drops at a constant flow rate in a closed environment, and the other group was exposed to dirty water in an open environment, and observed for 2 months. At the end of the process, sections of 50 × 80 × 200 cm³ were taken from the specimens and friction, abrasion and flexural tests were carried out. The results of the study demonstrate that a 7.5% pyrite substitution improves both flexural and shear strength by 38%. At the same time, pyrite substitution prevented algal growth on the surface of field concrete under clean water and delayed its formation in those under contaminated water. Finally, it was observed that pyrite, when used in concrete mix and surface applications, optimizes mechanical performance and environmental durability. Full article

To address the issues of high cost and poor low-temperature adaptability in cement-based backfill materials, this study developed a high-volume fly ash-based solid waste cementitious backfill material (FAPB) along with a specialized low-temperature admixture. Investigated the fundamental properties and microscopic curing mechanisms of the FAPB at different temperatures. The results indicate that the yield stress and plastic viscosity of FAPB slurry increase with higher contents of the curing agent and admixture, and rise as the temperature decreases. The variation in slump flow aligns with the rheological parameters, with the minimum slump flow being 14.5 cm (>10 cm). Bleeding rate increases with decreasing amounts of curing agent and admixture content, as well as lower temperatures, reaching a maximum bleeding rate of 9.26% (T5C10). Setting time decreases with increased amounts of curing agent and admixtures, and significantly increases with decreasing temperature. Strength increases with curing time and curing agent content, but decreases significantly as temperature drops. Adding admixtures can compensate for strength deterioration caused by low temperatures, with an optimal dosage of 3%. Microstructural analysis showed that the main hydration products of hardened backfill include AFt, C-S(A)-H, and Ca(OH)₂. Low temperature (5 °C) restricts hydration product formation, and the admixture facilitates continuous polycondensation of C-S(A)-H gel, resulting in sustained strength gain. This study provides a theoretical basis for the preparation and application of low-temperature-resistant Fly ash-based backfill materials, holding significant importance for advancing green mining practices in cold regions. Full article