Search Results (264)

Asphalt plant reclaimed powder is a common solid waste in road engineering. Reusing reclaimed powder as filler holds significant importance for environmental protection and resource conservation. The key factors affecting the feasibility of reclaimed powder reuse are its acidity/alkalinity and cleanliness. Traditional evaluation methods, such as the methylene blue test and plasticity index, can assess reclaimed powder properties to guide its recycling. However, these methods suffer from inefficiency, strong empirical dependence, and high variability. To address these limitations, this study proposes a rapid and precise evaluation method for reclaimed powder properties based on Fourier transform infrared spectroscopy (FTIR). To do so, five field-collected reclaimed powder samples and four artificial samples were evaluated. Scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), and X-ray diffraction (XRD) were employed to characterize their microphase morphology, chemical composition, and crystal structure, respectively. Subsequently, FTIR was used to establish correlations between key acidity/alkalinity, cleanliness, and multiple characteristic peak intensities. Representative infrared characteristic peaks were selected, and a quantitative functional group index (Is) was proposed to simultaneously evaluate acidity/alkalinity and cleanliness. The results indicate that reclaimed powder primarily consists of tiny, crushed stone particles and dust, with significant variations in crystal structure and chemical composition, including calcium carbonate, silicon oxide, iron oxide, and aluminum oxide. Some samples also contained clay, which critically influenced the reclaimed powder properties. Since both filler acidity/alkalinity and cleanliness are affected by clay (silicon/carbon ratio determining acidity/alkalinity and aluminosilicate content affecting cleanliness), this study calculated four functional group indices based on FTIR absorption peaks, namely the Si-O-Si stretching vibration (1000 cm⁻¹) and the CO₃²⁻ asymmetric stretching vibration (1400 cm⁻¹). These indices were correlated with conventional testing results (XRF for acidity/alkalinity, methylene blue value, and pull-off strength for cleanliness). The results show that the Is index exhibited strong correlations (R² = 0.89 with XRF, R² = 0.80 with methylene blue value, and R² = 0.96 with pull-off strength), demonstrating its effectiveness in predicting both acidity/alkalinity and cleanliness. The developed method enhances reclaimed powder detection efficiency and facilitates high-value recycling in road engineering applications. Full article

To reduce the carbon footprint of the concrete industry and promote a circular economy, this study explores the reuse of waste materials such as glass powder (GP) and nitrile rubber (NR) fibres in concrete. However, the inclusion of these waste materials results in lower compressive strength compared to conventional concrete, limiting their application to non-structural elements. To overcome this limitation, this study adopts the concept of confined concrete by developing concrete-filled steel tube (CFST) stub columns. In total, twelve concrete mix variations were developed, with and without steel tube confinement. GP was utilised at replacement levels of 10–30% by weight of cement, while NR fibres were introduced at 0.5% and 1% by volume of concrete. The findings demonstrate that the incorporation of GP and NR fibres leads to a reduction in compressive strength, with a compounded effect observed when both materials are combined. Steel confinement within CFST columns effectively mitigated the strength reductions, restoring up to 17% of the lost capacity and significantly improving ductility and energy absorption capacity. All CFST columns exhibited consistent local outward buckling failure mode, irrespective of the concrete mix variations. A comparison with predictions from existing design codes and empirical models revealed discrepancies, underscoring the need for refined design approaches for CFST columns incorporating sustainable concrete infill. This study contributes valuable insights into the development of eco-friendly, high-performance structural systems, highlighting the potential of CFST technology in facilitating the adoption of waste materials in the construction sector. Full article

This study explored the potential of reusing eggshell powders as a renewable activating agent for producing porous carbon materials from coffee husk. Carbonization and activation experiments were conducted by heating the samples at a rate of 10 °C/min up to 850 °C under a nitrogen atmosphere. A custom-designed double steel-mesh sample holder was used to hold approximately 2.0 g coffee husk on the top, with varying masses of eggshell at the bottom to achieve eggshells to coffee husk mass ratios of 2:1, 4:1, 6:1 and 8:1. The results demonstrated that CO₂ released from the thermal decomposition of the eggshell powder significantly enhanced pore development at 850 °C. Compared to the pore properties of carbon material produced without eggshell (e.g., BET surface area of 321 m²/g), the activated carbon samples exhibited substantially improved pore properties (e.g., BET surface area in the range of 592 to 715 m²/g). Furthermore, the pore characteristics improved consistently with increasing eggshell content. Observations by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) confirmed the structural and chemical transformations of the resulting carbon materials. Under optimal carbonization-activation conditions, the resulting carbon materials derived from coffee husk exhibited microporous structures and slit-shaped pores, as indicated by the Type I isotherms and H4 hysteresis loops. Full article

The Scalable and Expeditious Additive Manufacturing (SEAM) process is an advanced additive manufacturing (AM) technique that relies on the optimization of metal powder suspensions to achieve high-quality 3D-printed components. This study explores the critical role of dispersants in enhancing the performance of stainless steel (SS) 420 metal powder suspensions for the SEAM process by improving powder loading, recyclability, flowability, and consequent final part density. The addition of dispersant allows for increased powder contents while preserving stable rheological properties, thereby enabling higher powder loading without compromising the rheological characteristics required in the SEAM process. Previously, our team implemented a two-step printing strategy to address the segregation issues during printing. Nonetheless, the semi-cured layer was not recyclable after printing, resulting in a significant amount of waste in the SEAM process. This, in turn, leads to a considerable increase in material costs. On the other hand, the addition of a dispersant has been shown to enhance suspension stability, enabling multiple cycles of reuse. This novel approach has been demonstrated to reduce material waste and lower production costs. The enhanced flowability guarantees uniform suspension spreading, resulting in defect-free layer deposition and superior process control. Moreover, the dispersant’s ability to impede particle agglomeration and promote powder loading contributes to the attainment of a 99.33% relative density in the final sintered SS420 parts, thereby markedly enhancing their mechanical integrity. These findings demonstrate the pivotal role of dispersants in refining the SEAM process, enabling the production of high-density, cost-effective metal components with superior material utilization and process efficiency. Full article

Polymer residues can be reused in civil construction by partially replacing mineral aggregates in concrete, thereby reducing the extraction of natural resources. This study aimed to evaluate the use of powdered poly (ethylene terephthalate) (PET) and polyethylene (PE) residues, accumulated in shaving-mill filters during the extrusion of multilayer films used in food packaging, in the production of sealing masonry blocks. The PET/PE residues were characterized by Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Cylindrical specimens were produced in which part of the sand, by volume, was replaced with 10, 20, 30, 40 and 50% polymer residue. The cylindrical specimens were evaluated for specific mass, water absorption and axial and diametral compressive strengths. The 10% content provided the highest compressive strength. This formulation was selected for the manufacture of concrete blocks, which were evaluated and compared with the specifications of ABNT NBR 6136:2014. The concrete blocks showed potential for applications without structural function and were classified as Class C. The results, in line with previous investigations on the incorporation of plastic waste in concrete, underscore the promising application potential of this strategy. Full article

This study systematically investigates the utilization of marble industry waste—waste marble powder (WMP) as partial cement replacement and waste marble aggregates (WMA) as partial fine aggregate replacement—in self-compacting concrete (SCC). A detailed experimental program evaluated the effects of various replacement levels (5%, 10%, and 20% for WMP; 20%, 30%, and 40% for WMA) on compressive strength and durability, particularly resistance to aggressive sulfuric acid environments. Results indicated that a 5% WMP replacement increased compressive strength by 4.9%, attributed primarily to the filler effect, whereas higher levels (10–20%) led to strength reductions due to limited pozzolanic activity and cement dilution. In contrast, WMA replacement consistently enhanced strength (maximum increase of 11.5% at 30% substitution) due to improved particle packing and aggregate-paste interface densification. Durability tests revealed significantly reduced compressive strength losses and mass loss in marble-containing mixtures compared to control samples, with optimal acid resistance observed at 20% WMP and 40% WMA replacements. A comprehensive life cycle assessment demonstrated notable reductions in environmental impacts, including up to 20% decreases in Global Warming Potential (GWP) at 20% WMP replacement. A desirability-based eco-cost-mechanical optimization—simultaneously integrating mechanical strength, environmental indicators, and production cost—identified the 10% WMP substitution mix as the most sustainable option, achieving optimal balance among key performance criteria. These findings underscore the significant potential for marble waste reuse in SCC, promoting environmental sustainability, resource efficiency, and improved concrete durability in chemically aggressive environments. Full article

Concrete and mortar production consumes significant natural resources, leading to environmental concerns and sustainability challenges. Sustainable alternatives, such as industrial byproducts, have been explored to replace clinkers and aggregates. Basalt rock powder (BRP) is a promising option due to its physical and chemical properties, including its better particle size distribution and compatibility with cementitious composites, and studies have highlighted its pozzolanic activity and its potential to improve mechanical properties (compressive strength, flexural strength, and durability). Reusing rock dust as a raw material could transform it into a mineral byproduct, benefiting the new material and reducing waste volumes. This article presents a systematic literature review on the use of BRP in construction materials, conducted using the Scopus, ScienceDirect, PubMed, and Web of Science databases and following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) procedures. The search resulted in 787 articles (up to December 2024) and, after the screening process, 17 met the inclusion criteria. From the selected articles, information regarding the utilization of this waste product; its influence on mechanical properties, pozzolanic activity, and durability; and the sustainability associated with its use was compiled. The risk of bias was low as the search was comprehensive, all the papers were peer-reviewed, and all authors reviewed the papers independently. In conclusion, the studies demonstrate the potential of using BRP as a component of cementitious materials, indicating it as a possible innovative solution to the current challenges in the construction industry. Full article

Recently, graphene oxide (GO) has been largely investigated as a potential adsorbent towards dyes. However, the major obstacle to its full employment is linked to its natural powder consistence, which greatly complexifies the operations of recovery and reuse. With the aim to overcome this issue, the present work reports on the design of GO-modified carbon nanotubes buckypapers (BPs), in which the main component, GO, is entirely entrapped in the BP grid generated by CNTs for the double purpose of (a) increasing adsorption performance of GO-BPs and (b) ensure a fast process of regeneration and reuse. Adsorption experiments were performed towards several dyes: Acid Blue 29 (AB29), Crystal Violet (CV), Eosyn Y (EY), Malachite Green (MG), and Rhodamine B (RB) (C_i = 50 ppm, pH = 6). Results demonstrated that adsorption is strictly dependent on the charge occurring both on GO-BP and dye surfaces, observing great adsorption capacities towards MG (493.44 mg g⁻¹), RB (467.35 mg g⁻¹), and CV (374.53 mg g⁻¹), due to the best coupling of dye cationic form with negative GO-BP surface. Adsorption isotherms revealed that dyes capture onto GO-BPs is thermodynamically favored (ΔG < 0), becoming more negative at 313 K. Kinetic studies evidenced that the process can be described through a pseudo-first-order model, with MG, RB, and CV exhibiting the highest values of k₁. In view of these results, the following trend in GO-BP adsorption performance has been derived: MG ≈ RB > CV > AB29 > EY. Full article

Heavy metal and dye contamination from industrial wastewater present substantial dangers to both ecological systems and human well-being. This study explores the upcycling of Coffee Powder Trimmings (CPT), a biomass waste rich in oxygen-containing functional groups, for water remediation. CPT was first used to adsorb Cu²⁺ and Fe³⁺ ions, then pyrolyzed at 750 °C to form metal oxide biochar composites (Cu/CB and Fe/CB). Characterization confirmed the formation of CuO and Fe₃O₄ particles and the retention of key adsorption functionalities. The materials were evaluated for methylene blue (MB) removal across pH levels, various water bodies, and multiple reuse cycles. CPT effectively removed >95% of Cu²⁺ and Fe³⁺ via chelation, while Fe/CB achieved up to 97.8% MB removal due to synergistic π–π, hydrogen bonding, and coordination interactions. Both biochars retained high performance after five cycles, with Fe/CB maintaining 86.88% efficiency. These results highlight CPT-derived biochar as a sustainable, low-cost adsorbent for dual removal of heavy metals and dyes. Full article

In recent years, the rapid development of industry has led to the discharge of large quantities of pollutants, including harmful dyes, into water sources, thereby posing potential threats to human health and the environment. FeOCl and biochar have their own shortcomings as a mediator in the heterogeneous Fenton process. To make both materials useful, FeOCl supported on bamboo biochar (FeOCl/BC) was prepared by calcination using FeCl₃·6H₂O and bamboo powder as raw materials, and the composite’s catalytic activities were explored with acid orange II (AO-II) as the target pollutant. The degradation efficiency of FeOCl/BC composites on AO-II was determined by testing the mass ratio of FeOCl and BC, initial pH, temperature, H₂O₂ concentration, catalyst addition, addition of coexisting inorganic anions, and natural organic matter. The addition of biochar to FeOCl increased the activation of H₂O₂ to generate •OH for the removal of AO-II and accelerated the cycle of Fe³⁺/Fe²⁺. The removal rate of AO-II by the Fe₁C_0.2 composite was 97.1% when the mass ratio of FeOCl and BC was 1:0.2 (Fe₁C_0.2), which was higher than that of the pure components (FeOCl or BC) at pH = 6.1. Moreover, after five reuses, the Fe₁C_0.2 composite still showed high degradation activity for AO-II, with 83.3% degradation and low activity loss. The capture experiments on the active material showed that the removal of AO-II by the Fe₁C_0.2 composite was mainly dominated by •OH; however, •O₂⁻ and h⁺ played minor roles. The synthesized Fe₁C_0.2 composite could be applied for organic contaminants such as AO-II with high removal efficiency. Full article

This review analyzes TiO₂-based coatings formed by the plasma electrolytic oxidation (PEO) process of titanium for the photocatalytic degradation of methyl orange (MO) under simulated solar irradiation conditions. PEO is recognized as a useful technique for creating oxide coatings on various metals, particularly titanium, to assist in the degradation of organic pollutants. TiO₂-based photocatalysts in the form of coatings are more practical than TiO₂-based photocatalysts in the form of powder because the photocatalyst does not need to be recycled and reused after wastewater degradation treatment, which is an expensive and time-consuming process. In addition, the main advantage of PEO in the synthesis of TiO₂-based photocatalysts is its short processing time (a few minutes), as it excludes the annealing step needed to convert the amorphous TiO₂ into a crystalline phase, a prerequisite for a possible photocatalytic application. Pure TiO₂ coatings formed by PEO have a low photocatalytic efficiency in the degradation of MO, which is due to the rapid recombination of the photo-generated electron/hole pairs. In this review, recent advances in the sensitization of TiO₂ with narrow band gap semiconductors (WO₃, SnO₂, CdS, Sb₂O₃, Bi₂O₃, and Al₂TiO₅), doping with rare earth ions (example Eu³⁺) and transition metals (Mn, Ni, Co, Fe) are summarized as an effective strategy to reduce the recombination of photo-generated electron/hole pairs and to improve the photocatalytic efficiency of TiO₂ coatings. Full article

To mitigate the environmental effects of oil spills, a novel hydrophilic–oleophobic mixed-coated filter was developed for efficient oil–water separation and surface oil recovery. The coating consisted of titanium dioxide nanoparticles (TiO₂) and ultra-fine carbon black powder, deposited onto a 304 stainless-steel mesh substrate via spray deposition, followed by high-temperature sintering. This process induced a phase transition in TiO₂ from anatase to rutile, and formed a TiC khamrabaevite. The filter’s performance was evaluated using contact angle measurements and filtration tests with a motor oil–water mixture, while SEM, EDS, and XRD analyses characterized its morphology and coating structure. Contact angle testing confirmed that carbon modification significantly enhanced the oleophobicity of the TiO₂ filter, and SEM imaging demonstrated higher substrate coating adhesion, enabling multiple reuse cycles. These findings highlight the potential of TiO₂ carbon composite coatings in improving oil spill remediation technologies by offering a reusable and efficient filtration system. Full article

This study addresses environmental concerns by utilizing banana peel waste to develop innovative adsorbent materials for wastewater treatment, aligning with circular economy principles. Spherical beads were synthesized from sodium alginate mixed with various banana peel-based materials, including pure powder (PBP), activated carbon (AC), and magnetic activated carbon (MAC). These beads were evaluated for their efficiency in removing tetracycline (TC) and hexavalent chromium (Cr(VI)) as model pollutants representing antibiotics and heavy metals, respectively. Characterization of the beads revealed functional groups and thermal stability conducive to effective adsorption. Adsorption trials demonstrated that MAC beads achieved the highest removal efficiencies, up to 92% for TC and 79% for Cr(VI). The adsorption process followed pseudo-second-order kinetics and Langmuir isotherms. Remarkably, the beads retained a significant adsorption capacity across reuse cycles, indicating their regenerative potential. Comparisons with other adsorbents highlight the competitive performance of these banana peel-based materials. The results emphasize the potential of banana peel-derived adsorbents as cost-effective, sustainable solutions for mitigating emerging pollutants in water systems, promoting waste valorization and environmental protection. The research demonstrates a novel approach to sequential adsorption without intermediate regeneration, showing that the beads can effectively remove both tetracycline and chromium (VI) in successive cycles. This finding is particularly significant because it reveals that the presence of previously adsorbed chromium actually enhanced the beads’ capacity for tetracycline removal in the second cycle, suggesting a synergistic effect that had not been previously reported in the literature. These innovations contribute meaningfully to both waste valorization and water treatment technologies, offering new insights into the development of multi-functional adsorbents from agricultural waste materials. Full article

In additive manufacturing, particularly with Laser–Powder-Bed Fusion (L-PBF), augmenting recycled powder with virgin powder is common to extend lifespan. This practice complicates tracking recycling cycles, as parts consist of layers from both virgin and recycled powders. The virgin-to-recycled powder ratio significantly influences material properties, though limited research has explored the complexities of combining powders of varying qualities. In this study, we investigate how different ratios of virgin and recycled powders, along with leftover powder in the feed chamber, affect these properties. Using maraging steel powder, the virgin-to-recycled ratios were varied, examining impacts on powder characteristics and printed part quality. Leftover powder was analyzed for changes due to laser spatter and high temperatures, focusing on particle size and agglomeration. The results showed that exposure to laser spatter and heat increased particle size and agglomeration. Higher proportions of sieved powder resulted in larger particle sizes, while densely packed layouts led to oversized agglomerates due to concentrated laser exposure. Although mechanical properties remained stable, tensile strength was higher in parts made from virgin powder, negatively correlating with the reused powder content. Optimizing the virgin-to-recycled powder ratio can enhance sustainability in additive manufacturing without significantly degrading mechanical properties, offering insights critical for refining powder reuse strategies. Full article

The growing production of glass fibers is a major challenge due to the later problem of their sustainable recycling. This article reports the potential use of post-production waste glass fibers and basalt powder as additives in resin compounds designed for repairing concrete elements. The aim of this research was to develop a repair compound based on epoxy resin with the addition of waste materials, offering a competitive alternative to currently available repair compounds on the market by utilizing lower-cost materials and addressing pro-environmental aspects through waste reuse. The prepared research samples were characterized by varying proportions of basalt powder (0–20%), ground HP 12 fibers (40/60%), and HP 6 fibers (10/20%). A series of tests, including tensile strength tests, were conducted as part of this study to determine the effect of the applied additives on the ultimate tensile force and maximum deformations. Abrasion resistance tests were also carried out to evaluate the impact of basalt powder as a filler on enhancing the abrasion resistance of the designed repair compound. Additionally, SEM and EDS analyses were used to evaluate the uniformity and distribution of the additives within the sample. This study examined samples containing varying percentages of basalt powder and fibers, both virgin and milled. The most significant reinforcement effect was observed for sample E/20HP/20bp, where its tensile strength decreased by 8%, while its abrasion resistance increased by 44% compared to the reference sample. The obtained results confirm that incorporating waste materials as additives into epoxy resin can significantly enhance the mechanical properties of repair compounds while reducing cost and promoting environmental protection. In addition, the repair compound developed complies with the selected principles within the 6Rs environmental regulations: RECYCLING (reuse of waste glass fibers), RETHINK (reduce environmental impact by avoiding landfill), REDUCE (minimize the use of virgin glass fibers in the production of repair compounds) and REPAIR (increase the efficiency of repairing damaged concrete structures). Furthermore, as the percentage of basalt powder increases, the abrasion resistance of the repair compound improves. The obtained repair compounds may serve as an alternative to currently used compounds for the repair of bridges and factory floors. Full article