Search Results (7,850)

The construction industry plays a major role in the consumption of natural resources and the generation of waste. Construction and demolition waste (CDW) is produced in substantial volumes globally and is widely available. Its accumulation poses serious challenges related to storage and disposal, highlighting the need for effective strategies to mitigate the associated environmental impacts of the sector. This investigation intends to evaluate the influence of mixed CDW on the physical, mechanical, and durability properties of mortars with CDW partially replacing Portland cement, and allow performance comparisons with mortars produced with fly ash, a commonly used supplementary binder in cement-based materials. Thus, three mortar formulations were developed (reference mortar, mortar with 25% CDW, and mortars with 25% fly ash) and several characterization tests were carried out on the CDW powder and the developed mortars. The work’s principal findings revealed that through mechanical grinding processes, it was possible to obtain a CDW powder suitable for cement replacement and with good indicators of pozzolanic activity. The physical properties of the mortars revealed a decrease of about 10% in water absorption by immersion, which resulted in improved performance regarding durability, especially with regard to the lower carbonation depth (−1.1 mm), and a decrease of 51% in the chloride diffusion coefficient, even compared to mortars incorporating fly ash. However, the mechanical performance of the mortars incorporating CDW was reduced (25% in terms of flexural strength and 58% in terms of compressive strength), but their practical applicability was never compromised and their mechanical performance proved to be superior to that of mortars incorporating fly ash. Full article

While acetic acid has proven effective as a mild acidic treatment for removing adhered mortar from recycled concrete aggregate (RCA) surfaces, its potential for dissolving damage to the surface of the original natural coarse aggregate (NCA) within the RCA and its impact on the resultant concrete properties require careful consideration. This investigation systematically evaluates the effects of varying concentrations of dilute acetic acid solutions, commonly used in RCA treatment protocols, through a multi-methodological approach that includes comprehensive physical characterization, stylus and 3D optical profilometry, scanning electron microscopy (SEM), and nanoindentation analysis. The results show that even dilute acid solutions have an upper concentration limit, as excessive acid concentration, specifically 0.4 M, induces significant textural dislocations on NCA surfaces, creating millimeter-scale erosion pits that increase aggregate water absorption by 18.5%. These morphological changes significantly impair concrete workability and reduce compressive strength performance. Furthermore, microstructural analysis reveals a 45.24% expansion in interfacial transition zone (ITZ) thickness, accompanied by notable reductions in elastic modulus and microhardness characteristics. In practical RCA treatment applications, for RCA containing limestone-based NCA, it is recommended to use acetic acid concentrations between 0.1 and 0.3 M to avoid substantial physical and microstructural degradation of aggregates and concrete. Full article

Processed sea sand has emerged as a viable alternative to traditional fine aggregates in the Sri Lankan construction industry. Despite its economic and environmental advantages, concerns over residual seashell content have limited its widespread adoption by local contractors. Residual seashell content, typically ranging from 1% to 3% after processing, has raised concerns about its impact on the performance of concrete. This study systematically investigates the influence of seashell fragments, with a content of up to 5%, on the fresh, mechanical, and durability properties of sea sand concrete and mortar. Experimental results indicate that workability remains stable, with minor variations across the tested range of shell content. Compressive strength remains relatively consistent from 0% to 5% seashells, indicating that seashell content does not significantly impact the strength within this range. Durability tests reveal minimal effects of shell content on concrete performance within the tested shell range, as indicated by results for water absorption, rapid chloride penetration, and acid exposure testing. Accelerated corrosion indicates that the typical shell content does not increase corrosion risk; however, high shell content (>3%) can compromise corrosion durability. Overall, these findings demonstrate that the mechanical and durability performance of sea sand concrete remains uncompromised at typical seashell content levels (1–3%), supporting the use of processed sea sand as a sustainable and viable alternative to traditional fine aggregates in Sri Lankan construction. Full article

Wood polymer composites (WPCs) represent a rapidly growing class of sustainable materials, formed by combining lignocellulosic fibers with thermoplastic or thermoset polymeric matrices. This review summarizes the state of the art in WPC development, emphasizing the use of recyclable (or recycled) and biodegradable polymers as matrix materials. The integration of waste wood particles into the production of WPCs addresses global environmental challenges, including plastic pollution and deforestation, by offering an alternative to conventional wood-based and petroleum-based products. Key topics covered in the review include raw material sources, fiber pre-treatments, compatibilizers, mechanical performance, water absorption behavior, thermal stability and end-use applications. Full article

In this study, the water-repellent performance of Expanded Perlite (EP) coated with stearic acid (SA) at different coating/EP ratios (0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4% and 5%) and the capillary water absorption and thermal conductivity behaviors of the modified insulation mortars prepared at these different coating/EP ratios were investigated experimentally. In contrast to the existing literature, experimental studies were carried out for both coated and uncoated EP particles used in mortars to which water-repellent polymers were not added, and the minimum and maximum coating amounts showing the lowest capillary water absorption and slump were determined. In addition, the sustainability of modified insulation mortars consisting of EP-coated SA was determined by sustainable thermal performance (STP). In other words, this study is the first in the literature to determine how the thermal conductivity values of these mortars may change during their use in buildings. According to the experimental results, water absorption, which is an undesirable property, decreased significantly when coated with SA, and even SA-coated expanded coarse perlite (SCP) showed almost no water-absorption behavior at coating levels above 2%. The water-repellent performance of SCP was determined to be 83.2% between 0.1% and 0.4%. In addition, for coarse mortars (MCs), the best water-repellent performance was achieved at a 5% coating/EP ratio, with a 37% reduction in the capillary water-absorption coefficient. In addition, it was found that STP values increased as the coating/EP ratio increased. In other words, modified insulation mortars became more sustainable with an increasing SA coating/EP ratio. The highest STP values were observed in Groups 2 and 4 at a 5% coating/EP ratio, with MC-5 reaching 39.27% in Group 2 and MF-5 reaching 30.30% in Group 4. The results are important from a practical/industrial point of view and from a scientific point of view. Full article

A novel near-infrared (NIR) squaraine-based chemosensor, SQ-68, has been designed and synthesized for the sensitive and selective detection of Cu²⁺ and Ag⁺ ions, offering a compact solution for multi-analyte sensing. SQ-68 demonstrates high selectivity, with its performance influenced by the solvent environment: It selectively detects Cu²⁺ in acetonitrile and Ag⁺ in an ethanol–water mixture. Upon binding with either ion, SQ-68 undergoes significant absorption changes in the NIR region, accompanied by visible color changes, enabling naked-eye detection. Spectroscopic studies confirm a 1:1 binding stoichiometry with both Cu²⁺ and Ag⁺, accompanied by hypochromism. The detection limits are 0.09 μM for Cu²⁺ and 0.38 μM for Ag⁺, supporting highly sensitive quantification. The sensor’s practical applicability was validated in real water samples (sea, lake, and tap water), with recovery rates ranging from 73–95% for Cu²⁺ to 59–99% for Ag⁺. These results establish SQ-68 as a reliable and efficient chemosensor for environmental monitoring and water quality assessment. Its dual-analyte capability, solvent-tunable selectivity, and visual detection features make it a promising tool for rapid and accurate detection of heavy metal ions in diverse aqueous environments. Full article

Low-commercial-value natural pistachios (broken, closed, or immature) can be revalorised through oil extraction, obtaining a high-quality oil and partially defatted flour as by-product. This study evaluated the techno-functional and nutritional properties of the flours obtained by hydraulic press (HP) and single-screw press (SSP) systems, combined with pretreatment at 25 °C and 60 °C. The extraction method significantly influenced flour’s characteristics, underscoring the need to tailor processing conditions to the specific technological requirements of each food application. HP-derived flours presented lighter colour, greater tocopherol content, and higher water absorption capacity (up to 2.75 g/g), suggesting preservation of hydrophilic proteins. SSP-derived flours showed higher concentration of protein (44 g/100 g), fibre (12 g/100 g), and minerals, and improved emulsifying properties, enhancing their suitability for emulsified products. Pretreatment at 25 °C enhanced functional properties such as swelling power (~7.0 g/g) and water absorption index (~5.7 g/g). The SSP system achieved the highest oil extraction yield, with no significant effect of pretreatment temperature. The oils extracted showed high levels of unsaturated fatty acids, particularly oleic acid (~48% of ω-9), highlighting their nutritional and industrial value. The findings support the valorisation of pistachio oil extraction by-products as functional food ingredients, offering a promising strategy for reducing food waste and promoting circular economy approaches in the agri-food sector. Full article

The accumulation of end-of-life tires and the rapid increase in demolition activities pose significant environmental and waste-management challenges. The redevelopment of construction materials incorporating this waste is a potentially promising strategy for minimizing environmental impact while promoting the principles of a circular economy. This study investigates the performance of self-compacting concrete (SCC) incorporating up to 20% rubber aggregates (sand and gravel) and 40% recycled concrete aggregate (RCA) for non-structural applications. A series of tests was conducted to assess fresh and hardened properties, including flowability, compressive strength, tensile strength, flexural strength, water absorption, and density. The results indicated that increasing RCA content reduced density and compressive strength, while tensile and flexural strengths were only moderately affected. Response surface methodology (RSM), utilizing a Box–Behnken design, was employed to optimize compressive, tensile, and flexural strength responses. Statistical analysis was used to identify the optimal mix proportions, which balance the mechanical performance and sustainability of SCC with recycled components. Mixtures incorporating moderate rubber content—specifically, 5–5.5% sand rubber and 0–6% coarse rubber—and 40% recycled-concrete aggregate (RCA) achieved the highest predicted performance, with compressive strength ranging from 20.00 to 28.26 MPa, tensile strength from 2.16 to 2.85 MPa, and flexural strength reaching 5.81 MPa, making them suitable for sidewalks and walkways. Conversely, mixtures containing higher rubber proportions (5.5–20% sand rubber and 20% coarse rubber) combined with the same RCA level (40%) showed the lowest mechanical performance, with compressive strength between 5.2 and 10.08 MPa, tensile strength of 1.05–1.41 MPa, and flexural strength from 2.18 to 3.54 MPa. These findings underscore the broad performance range achievable through targeted optimization. They confirm the viability of recycled materials for producing environmentally friendly SCC in non-structural applications. Full article

With the growing severity of environmental pollution, people are paying increasing attention to their health. However, naturally occurring wood with health benefits and applications in human healthcare is still scarce. Natural wood exhibits a limited negative oxygen ion release capacity, and this release has a short duration, failing to meet practical application requirements. This study innovatively developed a humidity-responsive, healthy wood material with a high negative oxygen ion release capacity based on fast-growing poplar. Through vacuum cyclic impregnation technology, hexagonal stone powder was infused into the pores of poplar wood, endowing it with the ability to continuously release negative oxygen ions. The healthy wood demonstrated a static average negative oxygen ion release rate of 537 ions/cm³ (peaking at 617 ions/cm³) and a dynamic average release rate of 3,170 ions/cm³ (peaking at 10,590 ions/cm³). The results showed that the particle size of hexagonal stone powder in suspension was influenced by the dispersants and dispersion processes. The composite dispersion process demonstrated optimal performance when using 0.5 wt% silane coupling agent γ-(methacryloxy)propyltrimethoxysilane (KH570), achieving the smallest particle size of 8.93 μm. The healthy wood demonstrated excellent impregnation performance, with a weight gain exceeding 14.61% and a liquid absorption rate surpassing 165.18%. The optimal impregnation cycle for vacuum circulation technology was determined to be six cycles, regardless of the type of dispersant. Compared with poplar wood, the hygroscopic swelling rate of healthy wood was lower, especially in PEG-treated samples, where the tangential, radial, longitudinal, and volumetric swelling rates decreased by 70.93%, 71.67%, 69.41%, and 71.35%, respectively. Combining hexagonal stone powder with fast-growing poplar wood can effectively enhance the release of negative oxygen ions. The static average release of negative oxygen ions from healthy wood is 1.44 times that of untreated hexagonal stone powder, and the dynamic release reaches 2 to 3 times the concentration of negative oxygen ions specified by national fresh air standards. The water-responsive mechanism revealed that negative oxygen ion release surged when ambient humidity exceeded 70%. This work proposes a sustainable and effective method to prepare healthy wood with permanent negative oxygen ion release capability. It demonstrates great potential for improving indoor air quality and enhancing human health. Full article

Hydrogels exhibit remarkable physicochemical properties, including high water absorption and retention capacities, as well as controlled release behavior. Their inherent biodegradability, biocompatibility, and non-toxicity make them suitable for a wide range of applications. Cellulose, a biodegradable, renewable, and abundantly available polysaccharide, is a viable source for hydrogel preparation. Ionizing radiation, using electron-beam (EB) or gamma (γ) irradiation, provides a promising approach for synthesizing hydrogels. This study reviews recent advancements in cellulose-based hydrogels, focusing on cellulose and its derivatives, brief information regarding ionizing radiation, comparison between EB and γ-irradiation, synthesis and modification through ionizing radiation technology, and their environmental and agricultural applications. For environmental remediation, these hydrogels have demonstrated significant potential in water purification, particularly in the removal of heavy metals, dyes, and organic contaminants. In agricultural applications, cellulose-based hydrogels function as soil conditioners by enhancing water retention and serving as carriers for agrochemicals. Full article

The production of bionanocomposite films based on carboxymethyl derivatives of starch and cellulose with sodium montmorillonite (MMT-Na) as a filler was described. The developed films with high absorbency can be used in the preparation of adhesive dressings for wounds oozing as a result of abrasions or tattoos. Carboxymethyl cellulose (CMC), carboxymethyl starch (CMS), and potato starch were used as the raw materials for film manufacturing. Citric acid was used as a crosslinking agent and glycerol as a plasticizer. The following parameters were evaluated for the obtained films: solubility in water, swelling behavior, moisture absorption, and mechanical durability (tensile strength, elongation at break, and Young’s modulus). This study revealed that filler concentration has a significant influence on the stability, durability, and moisture absorption parameters of films. The best nanocomposite with a high absorption capacity was a two-component film CMS/CMC containing 5 pph of sodium montmorillonite and can be used as a base material for wound dressing, among other applications. Full article

Natural carbonate stones such as limestones and marbles are widely used in heritage and contemporary architecture, yet their durability is increasingly threatened by wildfire-related thermal stress. Since water transport plays a key role in stone deterioration, understanding how high temperatures affect hydric behavior is critical for conservation. This study investigates thirteen Portuguese carbonate lithotypes (including marbles, limestones, a travertine, and a breccia) exposed to temperatures of 300 °C and 600 °C. Capillary absorption and open porosity were measured, alongside Leeb hardness (HL) and ultrasonic pulse velocity (UPV), to evaluate their predictive capacity for post-fire moisture behavior. Results show that thermal exposure increases porosity and capillary uptake while reducing mechanical cohesion. Strong correlations between UPV and hydric parameters across temperature ranges highlight its reliability as a non-invasive diagnostic tool. HL performed well in compact stones but was less consistent in porous or heterogeneous lithologies. The findings support the use of NDT tests, like UPV and HL, for rapid post-fire assessments and emphasize the need for lithology-specific conservation strategies. Full article

In marine engineering applications, substituting conventional crushed stone coarse aggregates with coral aggregates offers dual advantages: reduced terrestrial quarrying operations and minimized construction material transportation costs. However, the inherent characteristics of coral aggregates—low bulk density, high porosity, and elevated water absorption capacity—adversely influence concrete workability and mechanical performance. To address these limitations, this investigation employed microbial-induced carbonate precipitation (MICP) for aggregate modification. The experimental design systematically evaluated the impacts of substrate concentration (1 mol/L) and mineralization period (14 days) on three critical parameters, mass gain percentage, water absorption reduction, and apparent density enhancement, across distinct particle size fractions (4.75–9.5 mm, 9.5–20 mm) and density classifications. Subsequent application trials assessed the performance of MICP-treated aggregates in marine concrete formulations. Results indicated that under a substrate concentration of 1 mol/L and mineralization period of 14 days, lightweight coral aggregates and coral aggregates within the 4.75–9.5 mm size fraction exhibited favorable modification effects. Specifically, their mass gain rates reached 11.75% and 11.22%, respectively, while their water absorption rates decreased by 32.22% and 34.75%, respectively. Apparent density increased from initial values of 1764 kg/m³ and 1930 kg/m³ to 2050 kg/m³ and 2207 kg/m³. Concrete mixtures incorporating modified aggregates exhibited enhanced workability and strength improvement at all curing ages. The 28-day compressive strengths reached 62.1 MPa (11.69% increment), 46.2 MPa (6.94% increment), and 60.1 MPa (14.91% increment) for the 4.75–9.5 mm, 9.5–20 mm, and continuous grading groups, respectively, compared to untreated counterparts. Full article

Environmentally friendly coated urea prepared using a waterborne polymer coating material is essential for promoting green and sustainable practices in modern agriculture. However, significant efforts are still urgently needed to address the undesirable properties of waterborne polymer coatings, i.e., poor hydrophobic properties and numerous micropores. Herein, dual nano-SiO₂ and siloxane-modified waterborne-polymer-coated urea was successfully developed. The characteristics of waterborne-polymer-coated urea before and after modification were compared. The results demonstrate that nano-SiO₂ and siloxane modification improved the hydrophobicity (water absorption decreased from 119.86% to 46.35%) and mechanical strength (tensile strength increased from 21.09 to 31.29 MPa, and the elongation at break exhibited an increase of 22.42%) of the waterborne polymer coatings. Furthermore, the –OH number of the modified coatings was decreased, while the coating surface formed a nano-scale rough structure, prolonging the nitrogen (N)-controlled release period from 7 to 28 days. Overall, the proposed novel dual-modification technique utilizing waterborne polymer coatings highlights the significant potential of eco-friendly coated urea with renewable coatings in modern agriculture. Full article

Per- and polyfluoroalkyl substances (PFASs) have gained significant attention due to their widespread distribution in the environment and potential adverse health effects. While ingestion, especially through contaminated drinking water, is considered the primary route of human exposure, recent research suggests that other pathways, such as inhalation and dermal absorption, also play a significant role. This review provides a concise overview of the toxicological impacts of both legacy and emerging PFASs, such as GenX and perfluorobutane sulfonic acid (PFBS), with a particular focus on their effects on the liver, kidneys, and immune and nervous systems, based on findings from recent in vivo, in vitro, and epidemiological studies. Despite the transition to PFAS alternatives, much of the existing toxicity data focus on a few legacy compounds, such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), which have been linked to adverse immune outcomes, particularly in children. However, evidence for carcinogenic risk remains limited to populations with extremely high exposure levels, and data on neurodevelopmental effects remain underexplored. While epidemiological and experimental animal studies supported these findings, significant knowledge gaps persist, especially regarding emerging PFASs. Therefore, this review examines the visceral, neural, and immunotoxicity data for emerging PFASs and mixtures from recent studies. Given the known risks from well-studied PFASs, a precautionary principle should be adopted to mitigate human health risks posed by this large and diverse group of chemicals. Full article