Papers by Keyword: Recycling

Abstract: The reuse of reclaimed asphalt pavement (RAP), sourced from the milling of existing pavements, offers an eco-friendly alternative to natural aggregates. It offers significant environmental benefits by reducing landfill waste and limiting the exploitation of natural resources. This study investigates the potential incorporation of fine RAP (FRAP) in the production of sand concrete, a particular type of concrete composed solely of fine aggregates. Firstly, five sand concrete mixtures were designed by partially or fully replacing natural sand with FRAP and were then assessed in terms of their mechanical characteristics and durability-related indicators. The results revealed that FRAP can be successfully used to produce sustainable sand concrete at replacement levels up to 50%, meeting all the mechanical performance requirements for pavement applications. The incorporation of FRAP also resulted in increased water absorption by immersion and higher sorptivity values. Yet, these values remained within the permissible limits for mixtures with 50% or less FRAP. Furthermore, given the critical role of elastic modulus in rigid pavement design, three predictive models were evaluated to estimate the elastic modulus of FRAP mixtures. The findings indicated that, when incorporating a correction factor reflecting aggregate quality, the ACI 318 model provided the highest accuracy, achieving a root mean square error of 1.5 GPa. The study confirmed the feasibility of reusing RAP in sand concrete, offering practical guidance for engineers to adopt this technique in pavement applications and encouraging greener construction practices.

Abstract: The structural-phase compositions of the alloy obtained through reduction melting with oxide waste use from the production of high-alloy steels and alloys with different charge compositions have been studied. It is crucial to determine the technological parameters that ensure the reduction of alloying element losses during the production and use of the alloying material. In the phase composition of the resulting alloy, a solid solution of alloying elements and carbon in the lattice of γ -Fe, Fe3C, as well as FeNi in the case of adding alloyed metal chips to the charge has been found.At the same time, a relative increase in the content of alloying elements in the studied areas of the alloy has been ensured (wt.%): Cr – from 1.84–32.90 to 0.59–43.98; Ni – from 1.41–20.74 to 4.24–45.02; Mo – from 0.35–1.30 to 0.00–11.89; W – from 0.00–0.08 to 0.00–21.37, respectively. This led to the formation of new phase structures containing refractory elements, presumably of carbide and intermetallic nature, which been observed in microstructural images. The proportion of residual carbon in the form of carbide component and residual unreacted reductant is aimed at providing the required reducing capacity during the alloy usage. The studies have identified new technological aspects of processing high-alloy industrial waste, resulting in a resource-efficient alloying material with the potential to partially replace standard ferroalloys in steel production.

Abstract: The research focused on investigating the physical and mechanical properties of stretch films containing recycled materials. The objective of the study was to examine how the use of recycled materials affects the structure and physical and mechanical properties of 5-layer stretch films. The results showed that incorporating up to 50% recycled materials in the stretch films can be a viable option for securing containers on pallets, provided that the film's composition is appropriately modelled using specific primary polymers in the film layers. The study employed extrusion methods to create the stretch films.

Abstract: The study emphasizes the interconnectedness of a healthy economy, equitable societies, environmental well-being, and the path towards sustainable development. While current sustainability assessments acknowledge ecological, social, and economic factors, they frequently miss the mark on space pollution and its related metrics. Space sustainability, envisioned as the peaceful and equitable access to and utilization of outer space, and is portrayed as a multi-faceted concept requiring consideration of various aspects to ensure responsible space conduct. Specifically, space debris in Earth's orbit poses a formidable challenge to achieving sustainable space activities, yet this critical dimension continues to be understudied within the broader sustainability framework. The study aims to fill this research gap by identifying Key Performance Indicators (KPIs) for evaluating product sustainability, emphasizing a comprehensive understanding across terrestrial and extraterrestrial dimensions. It advocates for integrating space-related factors into sustainability assessments, emphasizing the need for a holistic approach that spans both Earth's immediate environment and the broader universe. The proposed space-related KPIs aim to address unique challenges and opportunities associated with space activities. This study pushes the boundaries of sustainability, calling for a comprehensive approach that connects earthly principles with the vast reality of space. It emphasizes the need for responsible practices both on Earth and in orbit, highlighting the growing risks associated with space debris and advocating for effective space management strategies. For businesses, the study signifies a paradigm shift – challenging them to consider the impact of their activities on space sustainability by integrating the 'Dimension of Space' and its associated indicators into their sustainability frameworks. This holistic approach is critical for cultivating responsible space practices, ensuring the long-term viability of space exploration, and safeguarding our shared orbital commons for future generations. Keywords: Space Industry, Sustainable Practices, Space Product Eco-labeling and Certification, Mitigation Strategies, Pollution Reduction, Resource Recovery and Recycling.

Abstract: Nowadays, environmentally conscious manufacturers make their products from partly or fully recycled materials. However, recycling of polymer blends can be difficult. In immiscible polymer blends, the components often contain reactive functional groups, therefore polymers with reactive functional groups can be used as reactive compatibilizers. I investigated the mechanical, thermal, and morphological properties of different recycled rPET/rHDPE blends. I used an anhydride modified polyethylene (HDPE-g-MAH) as a compatibilizer. I found that without compatibilizer, the elongation at break decreased with the increase of rHDPE. As the amount of compatibilizer increases, the elongation at break is gradually increased. Furthermore, based on the SEM images, it can be observed that the size of the dispersed rHDPE phase in the rPET matrix decreased with the addition of a compatibilizer, and the dispersion of the dispersed phase also improved.

Abstract: Dross formation during the melting of twitch aluminium scrap using boric acid washing method, was investigated employing a Taguchi-based approach. The study aimed to analyse the impact of different treatment durations with a 1M concentration of boric acid on dross formation characteristics. Experimental trials involved treating twitch aluminium scrap samples with boric acid solutions for 15 to 60 minutes. Subsequently, dross formation characteristics were analysed using statistical techniques based on Taguchi analysis. Results unveiled significant variations in dross formation among treatment durations, indicating that longer treatment times led to decreased dross formation, particularly notable beyond the 30-minute mark. Taguchi's analysis confirmed the significance of treatment duration on dross formation, underscoring the effectiveness of the boric acid washing method in reducing dross formation during twitch aluminium scrap melting. This study offers valuable insights into optimising the boric acid washing method to diminish dross formation during twitch aluminium scrap melting, thereby enhancing efficiency and quality in aluminium recycling processes. Notably, the aim of the research systematically investigate the influence of treatment duration with a 1M concentration of boric acid on dross formation characteristics, providing practical guidance for implementing the boric acid washing method in industrial settings. Keywords: Dross, twitch aluminium scrap, boric acid, Taguchi analysis, recycling, waste management.

Abstract: Field-assisted sintering technology also known as spark plasma sintering is starting to be recognised as a potential route for metals processing and near net shaping for a range of sectors. FAST/SPS is an effective way of rapidly consolidating powder and particulate feedstocks, including waste streams such as machining swarf into shaped billets with as-forged properties. FAST/SPS can also be used as an intermediate step prior to conventional closed die forging or hot rolling (FAST-forge and FAST-roll, respectively). The solid-state technique has also been demonstrated to be an effective way to functionally grade and diffusion bond different alloys in the same FAST billet (FAST-DB). In this paper, we summarize some of the developments at The University of Sheffield around FAST/SPS over the last few years, with examples from different particulate types for a range of different sectors.

Abstract: In the process of iron production in a blast furnace, a large amount of dust is generated as a by-product. The main components of this dust include iron and carbon, so a circular process should be implemented to protect the environment and reduce production costs. In this investigation, blast furnace dust (BFD) was used to produce pellets with iron ore as raw charging materials into the blast furnace. The mixture consists of BFD, iron ore, and 2 % in mass of bentonite as a binder in the pelletization process, with the ratio of BFD in the mixtures with fine iron ore being 0:100, 10:90, 20:80, and 30;70, respectively. Green pellets were dried at 105 °C for 24 hours obtaining dried pellets. Dried pellets are fired at 1200 °C in the atmosphere for 60 minutes to achieve the required mechanical properties obtaining fired pellets. The fired pellets were reduced at 1000 °C and 1100 °C for 45 minutes by coke breeze. XRD and SEM were then used to analyze the properties of the pellets. The results showed that the pellets exhibited improved metallurgical properties, making them suitable for charging material into the blast furnace.

Abstract: A structural composite material is obtained by incorporating continuous and strong fibres in a polymer matrix. Such a design leads to materials with exceptional mechanical properties over a very small density. This family of composite materials can be extended further by combining special designs of composite sub-parts, like in honeycomb structures. Thanks to their performances, these composites are increasingly used in a range of applications mainly in the energy, construction, automotive and aerospace sectors. However, it is very difficult to dismantle composite materials in multi-material structures for recycling purposes; currently, they are mainly incinerated to produce energy. The present paper proposes adding “smart chemical additives” during composite manufacturing and assembly, which will facilitate both the separation of multi-material structures into single blocks, and the separation of composite sub-parts into raw materials. This innovative “debonding on-demand” function provides a significant incentive to using composite materials in a circular economy, i.e. promoting the repair, reuse and recycling of these materials.

Abstract: In this article, a regulatory processes study and technological properties of polyamide waste agglomerate modification is carried out. The legal support issues for polymer waste management in Ukraine are considered, ways to improve the most problematic aspects in this area are proposed. The technological properties of polyamide-6 waste agglomerate modification processes were studied in order to improve its technological and strength characteristics. MW-PA CB10 masterbatch modifier impact on the polyamide-6 waste agglomerate technological and strength characteristics complex was studied. It was established that the best is polyamide-6 waste agglomerate with 2 % wt. of masterbatch MW-PA CB10. For this composition the impact strength is 43.5 MPa, breaking stress during bending is 126.4 MPa, tensile strength is 342 N and elongation at break is 117 %. It can be recommended for reuse in traditional fields of primary polyamide-6 to obtain engineering and technical products.