Search Results (108)

This study evaluates the performance of asphalt concrete incorporating steel slag aggregates coated with recycled polyethylene terephthalate (PET). The aim was to enhance adhesion between aggregate and binder while addressing environmental concerns related to waste management. Laboratory testing was carried out to assess Marshall stability, indirect tensile strength, and tensile strength ratio, which are commonly used indicators of strength and moisture resistance in asphalt mixtures. The results showed that PET coating enhanced binder-aggregate bonding, resulting in higher stability, which indicates an improved resistance to plastic deformation and moisture damage compared to uncoated slag mixtures. Among the tested combinations, the mixes containing 20% slag with 10% PET and 30% slag with 15% PET demonstrated the most balanced performance. These mixes achieved greater durability while maintaining satisfactory strength values, indicating that PET-coated slag can serve as an effective partial replacement for natural aggregates in asphalt concrete. The study also highlights that the approach can help reduce reliance on natural stone, lower construction costs, and promote recycling of industrial byproducts and plastic waste. This contributes to more sustainable pavement practices while addressing issues of waste disposal and environmental degradation. The findings suggest that PET-coated steel slag can be considered a practical and resource-efficient material for asphalt mixtures. The research not only adds technical evidence to the growing interest in waste-based construction materials but also provides guidance for adopting such methods in developing countries, where cost and sustainability are critical factors. Full article

Accurate information on waste composition is essential for strategic planning in waste management and developing environmental technologies. However, detailed analyses of individual waste containers are both time- and cost-intensive, resulting in a limited number of available samples. Therefore, it is crucial to apply statistical methods that enable reliable estimation of average waste composition and its variability, while accounting for territorial differences. This study presents a statistical approach based on territorial stratification, aggregating data from individual waste container analyses to higher geographic units. The methodology was applied in a case study conducted in the Czech Republic, where 19.4 tons of mixed municipal waste (MMW) were manually analyzed in selected representative municipalities. The method considers regional heterogeneity, monitors the precision of partial estimates, and supports reliable aggregation across stratified regions. Three alternative approaches for constructing interval estimates of individual waste components are presented. Each interval estimate addresses variability from the random selection of waste containers and the selection of strata representatives at multiple levels. The proposed statistical framework is particularly suited to situations where the number of samples is small, a common scenario in waste composition analysis. The approach provides a practical tool for generating statistically sound insights under limited data conditions. The main fractions of MMW identified in the Czech Republic were as follows: paper 6.7%, plastic 7.3%, glass 3.6%, bio-waste 28.4%, metal 2.1%, and textile 3.0%. The methodology is transferable to other regions with similar waste management systems. Full article

This study explored the functionalization of sodium caseinate (NaCas) using environmentally friendly approaches to improve the mechanical and structural properties of the derived films. NaCas functionalization was achieved through casein crosslinking using two approaches: (i) thermal treatment at an alkaline pH to induce the formation of lysinoalanine (LAL) and (ii) riboflavin-mediated photo-oxidation to induce the formation of di-tyrosine (di-Tyr). Starting from NaCas (not functionalized, control) obtained from pasteurized milk, three functionalized NaCas samples were prepared: one sample crosslinked by LAL, and two samples crosslinked by di-Tyr formed under LED light either with or without riboflavin. The amount of crosslinking was evaluated in the acid hydrolysates through HPLC methods using either fluorescence (di-Tyr) or MS (LAL) detection. Heat treatment at pH 9 induced the formation of up to 3540 µg of LAL/g casein, whereas LED light exposure in the presence of riboflavin promoted the formation of up to 500 µg of di-Tyr/g casein. The formation of crosslinks at the intermolecular level, which resulted in protein aggregation, was detected by SDS-PAGE. Films were obtained by mixing the water solutions of the four NaCas samples with glycerol as the plasticizer and casting them. The FTIR spectra revealed that the formation of crosslinks also induced changes in the secondary structure of NaCas, which were conserved in the derived films. Mechanical testing demonstrated that di-Tyr crosslinks enhanced film ductility, while LAL crosslinks increased tensile strength and stiffness. Full article

The growing disposal of used tyres and plastic waste in landfills poses a significant environmental challenge. This study investigates the potential of utilizing used tyre rubber and macro-synthetic fibres (MSFs) made from recycled plastics in fibre-reinforced rubberized concrete (RuFRC). Various percentages of tyre rubber shreds were used to replace coarse aggregates, calculated as 10%, 20%, and 30% of the volume of fine aggregates; fibre dosages (0%, 0.25%, 0.5%, 0.75%, and 1% by volume) were incorporated into the mix, and a series of physical, mechanical, and durability properties were evaluated. The results show that, as the fibre and rubber content increased, the slump of RuFRC decreased, with the lowest value obtained for concrete with 1% fibre and 30% rubber. The density of RuFRC decreases as the rubber percentage increases due to air voids and increased porosity caused by the rubber. The strength properties of RuFRC were found to decline with the increase in the rubber content, with mixes containing 30% rubber exhibiting reductions of about 60% in compressive strength, 27% in tensile strength, and 13% in flexural strength compared to the control specimen. Durability testing revealed that an increased rubber content led to higher water absorption, water penetration, and chloride ion permeability, with 30% rubber showing the highest values. However, lower rubber content (10%) and higher fibre dosages improved the durability characteristics, with water absorption reduced by up to 5% and shrinkage strains lowered by about 7%, indicating better compaction and bonding. These results indicate that RuFRC with moderate rubber and higher fibre content offers a promising balance between sustainability and performance. Full article

Heparan sulfate proteoglycans (HSPGs) within the neuronal niche are expressed during brain development, contributing to multiple aspects of neurogenesis, yet their roles in glial lineage commitment remain elusive. This study utilised three human cell models expanded under basal culture conditions followed by media-induced lineage induction to identify a reproducible and robust model of gliogenesis. SH-SY5Y human neuroblastoma cells (neuronal control), ReNcell CX human neural progenitor cells (astrocyte inductive) and ReNcell VM human neural progenitor (mixed neural induction) models were examined. The cultures were characterised during basal and inductive states via Q-PCR, Western Blotting, immunocytochemistry (ICC) and calcium signalling activity analyses. While the ReNcell lines did not produce fully mature or homogeneous astrocyte cultures, the ReNcell CX cultures most closely resembled an astrocytic phenotype with ReNcell VM cells treated with platelet-derived growth factor (PDGF) biased toward an oligodendrocyte lineage. The glycated variant of surface-bound glypican-2 (GPC2) was found to be associated with lineage commitment, with GPC6 and 6-O HS sulfation upregulated in astrocyte lineage cultures. Syndecan-3 (SDC3) emerged as a lineage-sensitive proteoglycan, with its cytoplasmic domain enriched in progenitor-like states and lost upon differentiation, supporting a role in maintaining neural plasticity. Conversely, the persistence of transmembrane-bound SDC3 in astrocyte cultures suggest continued involvement in extracellular signalling and proteoglycan secretion, demonstrated by increased membrane-bound HS aggregates. This data supports HSPGs and HS GAGs as human neural lineage differentiation and specification markers that may enable better isolation of human neural lineage-specific cell populations and improve our understanding of human neurogenesis. Full article

Recycling plastics waste into concrete represents one of the possible approaches for its valorization, offering both economic and environmental benefits. Although numerous studies have explored the mechanical properties of concrete with plastics waste, its durability performance remains largely unexplored. In this context, this study aims to assess the electrochemical behavior of rebars embedded in reinforced concrete modified by partially replacing natural aggregates with recycled plastics, comparing their behavior to that of conventional concrete. The corrosion of reinforcing steel bars was evaluated by wet and dry cycles (w/d) in calcium chloride solutions, monitoring corrosion potential and potentiostatic polarization resistance, and recording electrochemical impedance spectroscopy (EIS) and polarization curves. In addition, the chloride diffusion tendency and the mechanical performances were assessed in unreinforced samples. The findings indicate that in environments with lower chloride concentrations, concrete with plastic granules provides good protection against rebar corrosion. Although the mechanical results of the studied mixes confirmed that incorporating plastic granules as aggregates in the concrete matrix causes a reduction in compressive strength, as known in the literature, the modified concrete also exhibits improved post-cracking behavior, resulting in enhanced ductility and fracture toughness. Full article

Aminotris(methylene phosphonic acid) (ATMP) and poly(acrylic acid) sodium salt (PAA) have shown favorable results in the treatment of porous building materials against weathering damage, showing promising potential as mixed-in additives during the production of lime-based mortars. This study investigates the impact of these additives on microstructure and mechanical properties. Additives were introduced in various concentrations to assess their influence on CaCO₃ crystallization, porosity, strength, and carbonation behavior. Results revealed significant modifications in the morphology of CaCO₃ precipitates, showing evidence of nanostructured CaCO₃ aggregates and vaterite stabilization, thus indicating a non-classical crystallization pathway through the formation of amorphous CaCO₃ phase(s), facilitated by organic occlusions. These nanostructural changes, resembling biomimetic calcitic precipitates enhanced mechanical performance by enabling plastic deformation and intergranular bridging. Increased porosity and pore connectivity facilitated CO₂ diffusion towards the mortar matrix, contributing to strength development over time. However, high additive concentrations resulted in poor mechanical performance due to the excessive air entrainment capabilities of short-length polymers. Overall, this study demonstrates that the optimized dosages of ATMP and PAA can significantly enhance the durability and mechanical performance of lime-based mortars and suggests a promising alternative for the tailored manufacturing of highly compatible and durable materials for both the restoration of cultural heritage and modern sustainable construction. Full article

This study presents a performance-based concrete mix design methodology rooted in the paste–aggregate binary framework, aiming to reduce binder content while ensuring optimal workability and strength. We found that inter-particle spacing (SPT) and paste rheology jointly govern fresh concrete behavior, with slump increasing nonlinearly with SPT and a critical transition zone around 20–35 µm; paste yield stress controls slump, while plastic viscosity governs segregation resistance. A two-level strength model was developed to predict concrete strength from paste properties based on compactness and hydration (R² = 0.90). Fixing SPT at 25 µm was identified as optimal for achieving balanced flowability with minimal paste volume. This approach effectively decouples aggregate packing optimization from paste calibration, offering a physically interpretable and practical framework for designing sustainable, low-carbon, and low-shrinkage concrete. Full article

Underground mining creates voids that require filling to prevent ground subsidence and mitigate post-mining issues. Traditionally, sand has been used as the primary backfilling material. However, the increasing demand from the construction sector and the slow natural replenishment of sand have necessitated the search for alternative materials. Researchers have explored fly ash (FA) as a potential substitute; however, its slow settling rate and the development of hydrostatic pressure limit its effectiveness. To address these issues, this study investigated the development of fly ash–plastic aggregate (FPA) as a suitable material for hydraulic backfilling by mixing FA with high-density polyethylene (HDPE) plastic in an 80:20 ratio. Initial investigations revealed that adding plastic as a binder significantly improves the physical, mechanical, and morphological properties of FA. The results further demonstrate that FPA satisfies and exceeds the standard requirements for hydraulic backfilling, as outlined in previous studies and case reports. These findings suggest that FPA is a promising alternative to both sand and FA for hydraulic backfilling applications. Full article

This study underscores the importance of sustainable practices by exploring the utilization of recycled plastic within the global construction industry. Plastic recycling has emerged as a crucial strategy that aligns with environmental, social, and economic sustainability indicators. Currently, substantial volumes of plastic waste are either deposited in landfills or incinerated, neglecting the potential to harness its embodied energy and the energy consumed for producing virgin materials. A key advantage of plastic lies in its promising mechanical properties. Concrete mix design is fundamental to a wide range of construction applications, including brick walls, reinforced concrete slabs, and concrete pavements. Despite the adoption of recycled plastic in construction materials in various countries, its widespread implementation remains limited. This is primarily due to the scarcity of experimental research in this area and the absence of a robust waste management system. This research specifically investigates the reuse of two common types of plastic waste: polyethylene terephthalate (PET) and high-density polyethylene (HDPE) to mitigate plastic waste accumulation in landfills and enhance the performance of construction materials. The study investigates the use of recycled HDPE and PET as a replacement for coarse aggregates in concrete pavement mixtures. While recycled PET is more prevalent in concrete applications, recycled HDPE has demonstrated exceptional efficiency and durability. The recycling method used in this research is the mechanical recycling method due to its superior effectiveness in comparison with other methodologies. This research assesses the performance of recycled PET and HDPE in concrete pavement, aiming to diminish non-renewable energy consumption by 15–20%, curtail the carbon footprint by 15–30%, and decrease plastic waste in landfills by 20–30% compared to conventional concrete. Full article

The scarcity of natural aggregates and the growing accumulation of waste materials have driven the demand for sustainable and circular economy solutions in transportation infrastructure, and this has led to the utilization of waste materials in transport infrastructure, such as recycled rubber. Although numerous laboratory experiments have been conducted on granular mixtures mixed with rubber, predicting the complex stress–strain behaviour of these mixtures mathematically and capturing the influence of rubber on the geotechnical properties of waste mixtures are imperative. This paper presents a comprehensive review of the constitutive models developed to predict the stress–strain behaviour, dilatancy, and shear strength of rubber-mixed waste materials, including sand–rubber, coal wash–steel furnace slag–rubber crumbs, and coal wash–rubber crumbs in various transport infrastructure applications under static loading. This paper also highlights the innovations and limitations of these existing constitutive models on rubber-mixed materials. It was found that existing constitutive models based on hyperbolic, hypoplastic, critical state, and bounding surface plasticity approaches can capture the behaviour of these materials under static loading conditions. However, further developments are required to incorporate the influence of the type and size of the rubber, particle breakage, and damping properties and also account for train-induced cyclic loading in models developed for railway substructures. This paper contributes to advancing future research aimed at deepening the fundamental understanding of rubber-mixed materials used in transportation infrastructure. Full article

This study explores the integration of recycled polypropylene (PP) plastic (PL) pellets into concrete mixtures, to evaluate their impact on compressive strength, workability, and weight reduction. Concrete samples were prepared by replacing conventional aggregates with PL pellets at varying percentages (1%, 3%, and 5%) by weight. The primary objective was to determine the optimal PL content that enhanced the properties of concrete. The experimental results demonstrated that incorporating 3% PP-PL pellets led to an 11.3% increase in compressive strength compared with the reference mix (0% PL). Furthermore, the 3% PL mix maintained a slump value comparable to that of the reference mix, indicating that this level of PL inclusion did not negatively affect workability. However, increasing the PL content beyond 3% resulted in a significant reduction in workability, suggesting that excessive PL may limit practical applications. The inclusion of PL pellets also contributed to a decrease in the overall weight of the concrete, showcasing the potential for producing lightweight, high-performance concrete. These findings highlight the feasibility of utilizing recycled PL in concrete production as a sustainable strategy to enhance material properties while addressing the growing issue of PL waste. This study identified 3% PL as the optimal dosage for achieving the best balance between strength, workability, and weight reduction. This research contributes to the development of more sustainable construction materials while also offering insights into the role of recycled PL in improving concrete performance. Future research could focus on evaluating the long-term durability, microstructural behavior, and environmental impact of PL-modified concrete to better understand its potential for broader application in eco-friendly infrastructure, ensuring it meets the demands of sustainable and cost-effective construction practices. In addition, this study’s findings pave the way for future investigations into optimizing other types of recycled PL for use in concrete. Full article

In Mexico, approximately 6.5 million tons of plastic waste is generated, of which 38–58% is improperly managed and has the potential to leak into the environment. Furthermore, producing natural aggregates is associated with the unsustainable use of non-renewable resources. In this sense, this work aimed to evaluate the influence that recycled aggregates from plastic waste have on the behavior of concrete. Coarse aggregates of thermoplastic paint (TP) from paving waste were prepared and incorporated into four mixes, with concentrations of 5 to 20%. In addition, three mixes with fine aggregates from PET were evaluated as one reference mix. The studied properties were slump, compressive strength, flexural strength, rebound number, density, absorption, and porosity. The results indicate that both aggregates have significant potential for use in concrete, including structural use, when replacement percentages of around 5% are considered, with property losses not exceeding 8%. Their use is proposed for active mobility infrastructure, with percentages of up to 20% analyzed in this study. Finally, it is necessary to analyze the influence that the incorporation of plastic waste has on mitigating environmental impacts, as well as the durability properties. Full article

The efficient separation and removal of carbon dioxide (${CO}_2$) from its mixtures is an important technological challenge to limit effects resulting from the increase of the carbon dioxide concentration in the atmosphere. Membrane technology is an environmentally friendly approach, highly scalable and less energy-consuming than conventional methods such as adsorption, absorption and cryogenic separation. Hybrid membrane materials incorporating inorganic filler nanostructures in polymer matrices having polyethylene glycol (PEG) as a plasticized additive are promising membrane materials given the presence of ${CO}_2$-philic polar functional groups of PEGs and the structural refinements on the blend matrix consequent to the filler distribution. In this review, literature information on hybrid polymer/PEG membranes are critically reviewed to discuss how filler dispersion in the blend matrix gives rise to enhanced ${CO}_2$ separation performances with respect to those obtained with traditional mixed matrix membranes where filler nanostructures are dispersed in the neat polymer. The discussion will be focused on the correlation between the ${CO}_2$ transport properties, membrane structural properties and defect resulting from the polymer-filler incompatibility. It is shown that hybrid polymer/PEG membranes with dispersed filler nanostructures simultaneously offer improved ${CO}_2$ separation performances and enhanced mechanical properties compared with nanocomposite ones where filler particles are dispersed in the neat polymer matrix. PEG addition enhances the filler-matrix compatibility, delays filler aggregation and limits the formation of filler-matrix interface defects. Full article

The use of waste, recycled, and modified materials is increasingly popular in roadway construction for sustainability and pavement longevity. This research examines the combination of steel slag (SS) and low-density polyethylene (LDPE), commonly used in plastic bags and steel manufacturing by-products, to mitigate environmental pollution. LDPE was tested as a binder modifier in two bitumen grades, 60–70 and 80–100, at concentrations of 3%, 5%, and 7% by weight. SS was used as a replacement for coarse aggregate. The physical properties of both modified and unmodified bitumen grades and SS were analyzed before creating and testing hot-mix asphalt (HMA) samples. The dynamic modulus of these samples was measured at temperatures of 4.4 °C, 21.1 °C, 37.8 °C, and 54.4 °C with frequencies of 0.1 Hz, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz, and 25 Hz. Master curves were developed, and the dynamic modulus data underwent design of experiment (DOE) and computational intelligence (CI) analyses. Using KENPAVE, a mechanistic–empirical tool, the analysis assessed the design life and enhancements in damage ratio for each modifier and grade. The results showed that adding LDPE increases the softening point and penetration grade but decreases ductility due to increased bitumen stiffness, leading to premature fatigue failure at higher LDPE levels. Both 3% LDPE and 3% SS-modified LDPE improved Marshall Stability and dynamic modulus across all temperature and frequency ranges. Specifically, 3% LDPE enhanced stability by 13–16% and 3% SS-LDPE by 30–32%. The KENPAVE results for 3% LDPE showed a design life improvement of 19–25% and a damage ratio reduction of 15–18%. In comparison, 3% SS-LDPE demonstrated a design life improvement of 50–60% and a damage ratio reduction of 25–35%. Overall, this study concludes that 3% LDPE- and 3% SS-LDPE-modified HMA in both bitumen grades 60–70 and 80–100 provide optimal results for improving pavement performance. Full article