Recycling Of Waste Materials Research Articles

Performance evaluation of controlled low-strength blended cement concrete modified with recycled waste materials

Purpose This work aims to investigate the feasibility of recycling waste plastic (polyethylene terephthalate) as a coarse aggregate for producing blended cement concrete modified with fly ash and pond ash. Design/methodology/approach The low, medium and high controlled strength blended cement concrete modified with varied proportions of fly and pond ashes were produced. Manufactured sand and recycled plastic coarse aggregate (RPCA) replaced normal fine and coarse aggregates. Concrete samples were tested for workability, mechanical and durability characteristics. Microstructural analysis was performed on cement concrete blended with fly and pond ashes and compared to conventional concrete samples. Findings All concrete mixes showed better flowability with values greater than 200 mm. Besides, the maximum flow time was approximately 8 s. The wet density of blended cement concrete-RPCA-based concretes was approximately 30% lower than that of conventional concrete. The compressive strengths of the controlled strength mix at 7 and 28 days were within the specified ranges. While the conventional concrete had slightly higher permeability, the blended cement concrete-RPCA-based concretes had better thermal resistivity and lower thermal conductivity. The scanning electron microscopy analysis revealed the densification of the microstructure due to the filler effects of fly and pond ashes. Originality/value This study establishes the prospects of substituting RPCA with normal coarse aggregate in the production of controlled low-strength blended cement concrete, offering benefits of structural fill concrete, lower permeability and thermal conductivity, higher thermal resistivity and reduced density and shrinkage.

Constitutive behaviour of a granular matrix containing coal mine waste intermixed with rubber crumbs

AbstractTraditional railway substructure materials (i.e., natural crushed rock aggregates used for ballast and capping layers) degrade under service loads, incurring higher periodic maintenance costs compared to recycled materials. Using recycled waste materials such as coal wash and rubber crumbs for infrastructure upgrades not only reduces construction and maintenance costs but also supports environmental sustainability. By exploring unconventional avenues, earlier studies have delved into the viability of blending rubber crumbs (RC) and coal wash (CW) as an innovative substitute for traditional railway substructure materials, with a specific focus on the capping layer. This study introduces a semi-empirical constitutive model to simulate the response of mixtures of coal wash and rubber crumbs (CWRC) using the bounding surface plasticity framework. The novelty of this study is that a modified volumetric strain expression is introduced to capture the compressibility of rubber, thus enabling a more accurate representation of the internal deformation of rubber within the granular matrix. The variation of rubber content in the mixture is captured by the corresponding critical state void ratio surface and the hardening modulus. The theoretical model is then calibrated and validated using static drained triaxial test data for CWRC mixtures as well as mixtures of steel furnace slag, coal wash, and rubber crumbs (SFS + CW + RC).

Optimum Use of Recycled Waste Materials as Partial Replacement of Fine Aggregate in Portland Cement Concrete Mixes

This study explored the independent utilization of five common waste materials - rubber, plastic, glass, slag, and sewage sludge ash (SSA) - as partial replacement of fine aggregate in Portland cement concrete (PCC) mixes. The main objective was to determine an optimum substitution range for each waste material that would offer well performing concrete in terms of workability, compressive strength, and durability. To this end, multiple concrete batches were prepared, incorporating each waste material at four different levels: 5%, 10%, 15%, and 20% by weight of fine aggregate. Then, concrete samples (100-mm diameter × 200-mm tall cylinders) were cast from each batch and were moisture-cured for 7, 14, and 28 days prior to testing. Also, the chemical composition of each waste material was identified using FTIR spectroscopy to understand its impact on the development of concrete strength. While most waste led to the diminished strength gains at all substitution rates, the addition of glass, slag, and SSA contributed positively to the strength development at specific replacement levels: 5% for glass, 10 - 15% for slag, and 5 – 15% for SSA. Furthermore, these additions of glass and slag exhibited comparable workability and durability although SSA did not exhibit comparable workability and durability. The findings of this study can hold significant implications for environmental sustainability and cost effectiveness in construction projects.

Integrating Management Strategy and Porter’s Five Forces Model for the Sustainable Recycling of Textile Waste

The purpose of this paper was to address the compatibility of management strategies with the competitive needs of textile waste recycling companies by applying Porter’s model. In conjunction with Porter’s model, it is appropriate to assess the attractiveness of the industry based on the balance of opportunities and threats, which determines whether the industry is attractive or less attractive. From this assessment, it is possible to decide whether to remain in the given industry and to identify strategies that indicate success. In terms of the European Green Agreement, it is necessary to ensure the faster and more efficient development of the circular economy, with a focus on resource-intensive sectors, including the textile industry. Given the adoption of the EU Strategy for Sustainable and Circular Textiles in June 2023, it is essential to address the issue of sustainable textile waste recycling. The importance of this strategy lies in strengthening the industry through reuse and repairs, as well as addressing the problem of textile waste. The prioritization of textile waste recycling has gained even greater importance with the arrival of the new automotive company, Volvo Cars, in eastern Slovakia. This development underscores the need for enhanced recycling efforts to manage the expected increase in industrial textile waste associated with the automotive sector’s expansion in the region. In Slovakia, four companies are involved in textile waste recycling: SK-TEX s.r.o., PR Krajné s.r.o., HOVEBA s.r.o., and LYKOTEX Slovakia s.r.o. This paper provides information on the possibility of expanding textile waste recycling capacities in eastern Slovakia. The quadratic graph method was used to identify an optimal location for textile waste recycling. The results of this analysis will help determine which enterprise in eastern Slovakia can enhance its competitiveness by leveraging this strategic location.

Effect of costus lucanius bagasse fibre on fresh and hardened concrete using RSM modelling

This investigation purposes to use the recycling waste materials in concrete to produce a sustainable environment for construction. The Costus lucanius bagasse fiber (CLBF) was utilized as supplementary cementitious material (SCM) to analyse the workability and mechanical properties of blended cement concrete. The concrete samples were made with the inclusion of 5–20% of CLBF at several w/c ratio by applying RSM modelling and optimization. Moreover, the cubical specimens were cast to study the compressive strength (CS), while beams were used to investigate the flexural strength (FS) on 28th days correspondingly. The outcomes show that the compressive and flexural strengths were decreased with rise in proportion replacement in concrete at various w/c ratio. The highest flexural and compressive strengths was attained at 5% of CLBF at 28 days respectively. Across the tested specimens, the values of compressive strength and flexural strength ranged from 30.20 to 53.92 N/mm2 and 2.15–8.81 N/mm2 for CLBF correspondingly. Besides, the workability and water absorption of concrete is getting decreased as the content of CLBF increases while it is recorded increasing as w/c ratio increases from 0.20 to 0.40. Furthermore, response model predictions were constructed and verified applying ANOVA at an acceptable level of significance of 95%. The coefficients of R2 for the mathematical models ranged from 98 to 99.99%. The research study also indicated that cement can be substituted by CLBF in the production of concrete for various construction purposes.

Performance Study of Stabilized Recycled Aggregate Base Material with Two-Gray Components.

This article studies the practical road performance of recycled materials from construction waste, relying on the paving test section of the supporting project for the Qingdao Cross-Sea Bridge. The research focuses on the construction technology and road performance of using recycled construction waste materials in urban road sub-base construction. Through indoor tests such as sieving and unconfined compressive strength tests, relevant technical indicators were obtained and analyzed. Additionally, periodic core sampling, compaction tests, and rebound deflection tests were conducted on-site according to relevant standards to thoroughly investigate the specific effects of using construction waste in practice and to analyze and evaluate the actual feasibility of the materials for road use. The results indicate that the particle gradation of the construction mix in the test section aligns well with the target gradation, and the dosage of the mixing agent meets the design requirements. The 7-day unconfined compressive strength already satisfied the technical requirements for heavy and extremely heavy traffic on highways as specified in the "Technical Specifications for Construction of Highway Pavement Subbase" (JTG/T F20-2015), with the 14-day strength generally reaching 7 MPa. Core sampling revealed good aggregate gradation, smooth and straight profiles, and the thickness and strength of all parts meet the specifications. The compaction levels met the testing requirements, the surface deflection values showed a decreasing trend, and the deformation resistance was good, consistent with the general development patterns of semi-rigid sub-bases.

A Study on Recycling Waste Materials in Construction Industry

The development of the construction industry has been greatly increasing over these decades. The high construction number produces several issues including waste. Waste materials in the construction industry have been one of the concerns due to high generation and most of them ended up in landfill. However, it is believed that these waste materials are recyclable. It is also adequate to be used in the construction industry for environmental sustainability as well as to reduce dependence on natural resources. Therefore, the primary objective of this research is to identify practices applied in the construction industry in recycling waste materials. Moreover, this study also serves the purpose to analyse the advantages and disadvantages of the common practices applied in recycling waste materials. Last but not least, it is expected as well throughout this study, that a recommendation may be made based on the effectiveness of recycling. To test the theories, an online questionnaire survey was conducted with 66 respondents from experts in the construction industry. The collected data further will be analysed using Statistical Package for Social Sciences (SPSS) version 26.0 software. From the results, the majority of the construction industry companies in Malaysia are aware of the waste management issue and practice waste materials recycling. The most recycled wastes are paper, cardboard, timber, and metal while the least recycled wastes are glass and asphalt due to their difficulties. Some of the waste categories are recycled by direct reuse methods such as timber and cardboard. Moreover, there is still room to improve the effectiveness of the current recycling system specifically in terms of operational cost. The current recycling system is beneficial in terms of resources, economic, and natural resource dependencies. Furthermore, the quality and reliability of the recycled products still need further improvement to be used as the main materials in the construction industry.

Study on use of recycled waste materials on the performance of asphalt binder and mixes: A comprehensive review

All aspects of daily living frequently involve the use of plastics. Due to the lack of effective waste treatment methods, massive global environmental problems will be caused by the accumulation of waste plastics. The use of waste materials in road building is of tremendous interest since it has the potential to reduce hazards and pollution while conserving natural resources. High-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), ethyl vinyl acetate (EVA), and polyvinyl chloride are the most appropriate and relevant of waste plastics. There are other types of waste materials used in the asphalt such as reclaimed asphalt pavement (RAP), crumb rubber (CR), steel slag, glass powder etc. These all-waste materials have been briefly discussed. In this review article several concerns have been raised about the physical and chemical qualities, of asphalt pavements that have been mixed with waste materials. Using waste materials in asphalt pavements can raise several concerns regarding the physical and chemical qualities of the resulting mixtures. These concerns typically revolve around factors such as durability, performance, environmental impact, and overall sustainability. This research article provides a thorough analysis of the wet and dry procedures used to mix different types of waste plastics. Overall, including waste plastics into asphalt mix improved rutting, fatigue, and moisture resistance. Additionally, recycling waste plastics in this manner helps in reducing environmental pollution and conserving natural resources. Overall, the inclusion of waste plastics in asphalt mixtures can contribute to the development of more sustainable and durable pavements with improved performance in terms of rutting, fatigue, and moisture resistance. There are still certain issues like compatibility and low temperature performances that need to be addressed. To overcome the aforementioned issues, many strategies are used, including the use of nanomaterials, chemical additives, and polymer additives. Additional research should be conducted to investigate the ageing effect, pavement performance monitoring, polymer stability, and the economic and environmental considerations associated with the usage of plastics in asphalt pavements.

Sustainable multi-story building design utilizing recycled marble and ceramic waste

This study explores the design of a multi-story structure utilizing recycled waste materials. Locally produced materials from recycled sources were used for making concrete and bricks. The design of a 10-story building was carried out using ETABS software. In the process, 10% of the cement in the concrete was replaced with waste marble powder (WMP), while the bricks were made by replacing 12% of clay with waste ceramic powder and 15% with waste brick powder. The materials were developed in a laboratory, adhering to ASTM standards, and their properties were input into the software for analysis and design. The results were compared to a structure made with traditional materials. The analysis showed that using recycled materials led to the conservation of 164 tons of cement and 475 cubic meters of fertile clay while maintaining the required stability standards as per building codes. The design also prevented the release of 148 tons of carbon dioxide into the atmosphere and reduced the energy demands associated with cement production. Additionally, the building utilizing waste materials was found to be Rs. 5.8 million more economical than one made with conventional materials.

Recovery of pure PET from wool/PET/elastane textile waste through step-wise enzymatic and chemical processing

Textile waste is mostly incinerated because few recycling processes are available to recover valuable materials. In this work, a feasible chemo-enzymatic recycling process of wool/polyethylene terephthalate (PET)/elastane blends to recover pure PET is for the first time successfully demonstrated. Two novel enzyme formulations were selected for wool hydrolysis, whereas the recovered amino acids were quantified using high-performance liquid chromatography and two assays (Ninhydrin and Folin–Ciocalteu). Kinetic studies on the amino acid formation alongside reaction observations by scanning electron microscopy proved sufficient removal of wool within 8 hours with the new enzyme formulation, marking an acceleration compared to previous studies. Finally, elastane was separated with a non-hazardous solvent to obtain pure PET. Tensile tests on the recovered PET fibres reveal only slight changes through the enzymatic treatment and no changes induced by the applied solvent. The enzyme formulation was successfully tested on five different post-consumer wool/PET textile waste samples. This valorization approach enhances the circular economy concept for textile waste recycling.

Preliminary Study of Stone Sawing Sludges-based Alkali Activated Materials (AAMs) for the Conservation of Archaeological Ceramics

This paper presents research into the feasibility of using stone sawing sludge-based Alkali Activated Materials (AAMs) for conservation of Cultural Heritage. Sawing sludges are a stone processing waste product resulting from the mixing of rock powder with the water used to cool down the cutting blades. The chemical composition of the sawing sludges, when aluminosilicatic, is suitable for acting as a precursor to produce AAMs. AAMs are known for their low environmental impact and versatility since their existence is drawn from recycling waste materials. One of their possible applications is in the conservation of Cultural Heritage objects. This work presents a preliminary investigation into three sawing sludge-based AAMs with different mineralogical compositions and contributes to formulating guidelines for applying them as fillers on modern and archaeological ceramic pottery based on the evaluation of their workability, appearance and physical properties over time from the moment of application and up to 30 days. Dynamic Vapor Sorption and X-Ray Diffraction results provided an overview of the structural and mineralogical changes under high RH conditions, where the tested AAMs showed a type II isotherm curve, as expected for concrete-like materials, as well as disappearance of thermonatrite after one isothermal cycle. Ultrasonic Pulse Velocity test demonstrated the general homogeneity of the AAMs despite the lower velocity exhibited by one of the formulations, probably due to its internal pore distribution and possible presence of microstratification. The Oddy tests, application tests and colourimetric measurements evidenced the advantages and weaknesses of the AAMs, with overall encouraging results ensuing investment in further in-depth studies of these innovative conservation materials in view of their future use in the field of conservation of Cultural Heritage as a result of a circular economy model.

Pilot Studies to Produce Steel from Mill Scale: Novel Approach to Recycle Waste Material

Pilot Studies to Produce Steel from Mill Scale: Novel Approach to Recycle Waste Material

Investigating a siderophore-based approach for the recovery of critical metals from waste streams and leach solutions using microorganisms

As technological advancements progress and unsustainable consumerism of electrical devices rapidly increases, the demand for critical metals continues to rise. The limited supply of these metals, driven by the depletion of non-renewable natural resources, calls for the recycling of waste materials and the development of sustainable and cost-effective extraction methods. Conventional methods of leaching such as pyrometallurgy pose threats to the environment by creating slags and releasing toxic secondary materials. Biohydrometallurgy emerges as an environmentally friendly method to extract metals from low-grade ores and waste material. Siderophores are secondary metabolites secreted by microorganisms that have the ability to selectively chelate certain metals. By immobilizing these siderophores for subsequent bioleaching, target metals can be extracted from multielement solutions. This research focuses on optimizing the immobilization efficiency of the siderophore desferrioxamine B (DFOB) in sodium alginate using physical entrapment for the removal of gallium. Four parameters were varied to find optimal conditions: sodium alginate concentration (1 – 4 % w/v), calcium chloride concentration (1 – 10% w/v), agitation time (0.25 – 10 hours), and DFOB concentration (1 – 4 mM). Using UV-Vis spectroscopy, free siderophore concentration could be determined. After 30 runs, the highest immobilization yield of 80.05% was determined at 2.5% sodium alginate, 10% calcium chloride—the highest concentration tested—after 5.13 hours with a concentration of 2.25 mM DFOB. Design Expert-13 software was used to analyze all experimental results. 2D graphs support that DFOB immobilization depends on responsive parameters, CaCl2 demonstrating the largest impact.

Cost-effective walnut shell biosorbent for efficient Cr(VI) removal from water: Batch adsorption and optimization using RSM-BBD

The conversion or recycling of waste materials into usable products is a sustainable and ecologically benign strategy, aligning with sustainable development and circular economy principles. This study presents a straightforward and cost-effective method for transforming walnut shells, commonly found in agricultural waste, into a biosorbent material highly effective in eliminating hexavalent chromium (Cr(VI)) from water. The prepared material underwent several analyses to determine its physical characteristics and surface chemistry, revealing an amorphous structure similar to lignocellulosic materials. Using Response Surface Methodology (RSM-BBD), we accurately forecasted and optimized the Cr(VI) adsorption process, evaluating and enhancing factors such as pH, biosorbent dosage, pollutant concentration, and adsorption time. Significant enhancement in the removal percentage (%R) was achieved, reaching 100 % after optimization. The RSM-BBD model provided high-quality prediction for data fitting (R² = 0.999). Various kinetic models, including PFO, PSO, and IPD models, were employed, with the PSO model providing the best depiction of adsorption. Equilibrium data analysis using the Langmuir, Freundlich, Redlich-Peterson and Temkin models revealed that the Freundlich model and R-P better fit the adsorption isotherm of Cr(VI) on treated walnut shell (WST). Furthermore, examination of Gibbs free energy and enthalpy indicated that the adsorption of Cr(VI) onto walnut shells is a spontaneous and exothermic reaction, resulting in the release of thermal energy.

A Promising Recycling Strategy via Processing Polypropylene/Recycled Poly(ethylene terephthalate): Reactive Extrusion Using Dual Compatibilizers.

Enhancing interfacial adhesion in polypropylene (PP)/recycled polyethylene terephthalate (rPET) blends is crucial for the effective mechanical recycling of these commercial plastic wastes. This study investigates the reactive extrusion of PP/rPET blends using a dual compatibilizer system comprising maleic anhydride grafted polypropylene (PP-g-MA) and various glycidyl methacrylate (GMA)-based compatibilizers. The effects of backbone structure and reactive group on the morphological, mechanical, and thermal characteristics were systematically studied. This study sheds light on the effective compatibilization mechanisms using characterization methods such as Fourier Transform Infrared Spectroscopy (FTIR) and morphological analyses (SEM). The results indicate that GMA-based compatibilizers play a bridging role between rPET and PP-g-MA, resulting in improved compatibility between the blend components. A combination of 3 phr PP-g-MA and 3 phr ethylene-methyl acrylate glycidyl methacrylate terpolymer (EMA-GMA) significantly improves interfacial adhesion, leading to synergistic enhancements of mechanical performance of the blend, up to 217% and 116% increases in elongation at break and impact strength, respectively, compared to the uncompatibilized sample. Moreover, a significant improvement in onset temperature for degradation is observed for the dual compatibilized sample, with 40 °C and 33 °C increases in onset temperature relative to the uncompatibilized and the single compatibilized samples. These findings underscore the immense potential of tailored multi-component compatibilizer systems for upgrading recycled plastic waste materials.

A Mapping of Textile Waste Recycling Technologies in Europe and Spain

A Mapping of Textile Waste Recycling Technologies in Europe and Spain

Development of a Non-Structural Prefabricated Panel Based on Construction and Demolition Waste for Sustainable Construction

The study focuses on developing a prefabricated panel for non-structural purposes by optimizing mortar mix designs incorporating recycled microplastic (RMP) and construction demolition waste (CDW) at various ratios (0, 10, 20, 30, and 100%). Experimental procedures encompassed material characterization, mortar specimen manufacturing, compression resistance testing, and thermal/acoustic panel tests following Colombian technical standards. Results indicate that incorporating 20% CDW enhances material strength, with cylinder number 3 (20% of CDW) achieving a resistance of 31.45 MPa. Panels incorporating recyclable waste materials show improved acoustic and thermal insulation properties, with up to 39 dB reduction in sound transmission and a 21 °C decrease in thermal transmission observed (5.6% and 35% for panel and door, respectively). This research advances sustainable construction practices demonstrating the potential of prefabricated panels using recyclable materials, offering eco-friendly solutions with enhanced performance characteristics for construction applications.

Liberation of Cathode Active Materials by Grinding Process for Direct Recycling of Waste Materials from Lithium Ion Battery Manufacturing Process

Liberation of Cathode Active Materials by Grinding Process for Direct Recycling of Waste Materials from Lithium Ion Battery Manufacturing Process

Influence of Waste Rubber Nano-Material Utilization on The Engineering Properties of Asphalt Matrix

Abstract The highway pavement construction industry is widely recognized as the most suitable establishment for recycling waste materials. Consequently, selecting sustainable materials constitutes a crucial concept for developing an innovative pavement construction characteristic. This research investigation aims to explore the consequences of utilizing waste rubber nanomaterial as a sustainable supplementary at four various weight ratios (0.5, 1, 1.5, and 2) in bituminous material. The assessment involved physical features such as viscosity, ductility, penetration, penetration index, and softening point. A dry mixing process is also accomplished for modified asphalts by conducting a high shear mixer at 5000 rpm for 30 minutes at 160 °C was chosen to ensure optimal dispersion of the waste rubber nanomaterial. Overall, the results demonstrated that adding waste rubber nanomaterial increased viscosity and softening point temperature but decreased ductility and penetration. The enhanced penetration index values of the modified asphalts result from the incorporation of residual rubber nanomaterial. In contrast, the binder modified with 2% residual rubber nanomaterial and nano-rubberization exhibited a greater penetration index (PI); thus, it positively impacts the resistance to rutting failure.

Temperature Optical Sensor Made of Recycled Waste Materials and Implementation of Machine Learning Method to Expand Its Measurement Range

Temperature Optical Sensor Made of Recycled Waste Materials and Implementation of Machine Learning Method to Expand Its Measurement Range