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Incorporation of E-Waste Plastics into Asphalt: A Review of the Materials, Methods, and Impacts: History
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Contributor: Sepehr Mohammadi , Dongzhao Jin , Zhongda Liu , Zhanping You

This paper presents a comprehensive review of the environmentally friendly management and reutilization of electronic waste (e-waste) plastics in flexible pavement construction. The discussion begins with an overview of e-waste management challenges and outlines key recycling approaches for converting plastic waste into asphalt-compatible materials. This review then discusses the types of e-waste plastics used for asphalt modification, their incorporation methods, and compatibility challenges. Physical and chemical treatment techniques, including the use of free radical initiators, are then explored for improving dispersion and performance. Additionally, in situations where advanced pretreatment methods are not applicable due to cost, safety, or technical constraints, the application of alternative approaches, such as the use of low-cost complementary additives, is discussed as a practical solution to enhance compatibility and performance. Finally, the influence of e-waste plastics on the conventional and rheological properties of asphalt binders, as well as the performance of asphalt mixtures, is also evaluated. Findings indicate that e-waste plastics, when combined with appropriate pretreatment methods and complementary additives, can enhance workability, cold-weather cracking resistance, high-temperature anti-rutting performance, and resistance against moisture-induced damage while also offering environmental and economic benefits. This review highlights the potential of e-waste plastics as sustainable asphalt modifiers and provides insights across the full utilization pathway, from recovery to in-field performance.

  • electronic waste
  • e-waste
  • e-waste plastics
  • plastic-modified asphalt
  • e-waste plastic-modified asphalt
  • rheological performance
Rapid global economic growth and technological advancements have led to the continuous introduction of new electrical and electronic products, rendering older devices obsolete at an accelerating rate. In recent years, growing urbanization, increased mobility, further industrialization, and higher levels of disposable incomes have led to a rapid increase in the consumption of electronic equipment worldwide. With the ongoing expansion of the global electronic equipment market, the lifespans of equipment are getting shorter. After the usage and disposal of electronic equipment, a complex waste stream emerges, comprising both toxic substances and recoverable resources. This waste stream, which includes common electronic products such as computers, televisions, monitors, VCRs, copiers, fax machines, hard drives, and other similar products, is referred to as electronic waste (e-waste). E-waste is growing at an accelerating pace annually and is now recognized as the fastest-growing form of waste globally [1][2][3][4][5].
End-of-life processing for this waste stream is an extremely challenging problem worldwide owing to its high consumption rate, large volume, short lifespan, and non-biodegradable structure. Moreover, the rapid growth of this technology is resulting in the obsolescence of many electronic products each and every day. According to the Global E-waste Monitor 2020 report, an estimated 53.6 million metric tons (Mt) of e-waste were generated globally in 2019 alone. This marks an increase of 9.2 Mt since 2014, with projections indicating that the total volume could reach 74.7 Mt by 2030. In stark contrast, only 9.3 Mt of e-waste, representing just 17.4% of the total generated, was formally documented as collected and recycled in 2019. The data reveal that e-waste recycling efforts are falling behind the rapid global increase in its generation. Rising e-waste levels present significant threats to environmental and public health, since many hazardous substances, including toxic metals such as barium (Ba), beryllium (Be), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), lithium (Li), and mercury (Hg), as well as persistent organic pollutants (POPs) such as dioxin, brominated flame retardants (BFRs), and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), are associated with these streams [2][6]. On the other hand, e-waste contains various valuable materials, including plastics that can be recovered and reused. However, recycling plastics from e-waste, which can account for up to 20% of the total stream, poses greater challenges than conventional plastic recycling, primarily due to the presence of BFRs [5][7]. Therefore, it is vital to not only increase the collection and recycling rate of e-waste and its environmentally friendly management but also identify alternative applications where e-waste can be utilized in a sustainable manner [2][8].
At the same time, the use of different waste products in asphalt binders and mixtures has become widespread due to their environmental and economic benefits. In recent years, researchers in the asphalt industry have placed a special emphasis on the utilization of different waste materials, such as waste plastics, waste crumb rubber, or bio-oils from different sources, in road pavements to not only alleviate the landfilling problems of these waste materials but also turn them into value-added new materials that can enhance the performance and durability of the pavements [9][10][11][12][13].
The use of waste plastics in road pavements is receiving growing attention, driven by the enhanced performance of asphalt binders and mixtures modified with plastic waste, as well as the associated economic and environmental benefits [9]. The use of e-waste plastics in road pavement applications has been the subject of growing interest among researchers. Reutilizing these non-degradable and potentially hazardous materials in pavement construction not only helps alleviate the burden on landfills and reduce environmental impacts but also contributes to significant resource savings [8][14].
This study explores how e-waste plastics can be integrated into asphalt production by examining and reviewing each stage of their reuse process, from the recovery stage of the plastics to their performance. After briefly discussing multiple perspectives on e-waste generation, handling, reuse, and the associated problems and challenges with these procedures, e-waste plastic recycling methods, as well as the available e-waste plastics for utilization in the asphalt industry and their incorporation methods, are reviewed.
Another part of the discussion also focuses on several key stages with the potential to significantly impact binder-plastic compatibility and the overall performance of e-waste plastic-modified asphalt binders. The study then evaluates the impact of e-waste plastics on the fundamental and rheological characteristics of asphalt binders, along with the mechanical performance of the resulting modified mixtures.
A review of the different stages in the utilization process of e-waste plastics can provide a better understanding of how to successfully incorporate these waste materials into road construction.

This entry is adapted from the peer-reviewed paper 10.3390/encyclopedia5030112

References

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  2. Forti, V.; Balde, C.P.; Kuehr, R.; Bel, G. The Global E-Waste Monitor 2020: Quantities, Flows, and the Circular Economy Potential; United Nations Institute for Training and Research: Geneva, Switzerland, 2020.
  3. Kumar, A.; Holuszko, M.; Espinosa, D.C.R. E-waste: An overview on generation, collection, legislation and recycling practices. Resour. Conserv. Recycl. 2017, 122, 32–42.
  4. Shahabuddin, M.; Uddin, M.N.; Chowdhury, J.I.; Ahmed, S.F.; Uddin, M.N.; Mofijur, M.; Uddin, M.A. A review of the recent development, challenges, and opportunities of electronic waste (e-waste). Inst. Ion. 2023, 20, 4513–4520.
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  7. Ma, C.; Yu, J.; Wang, B.; Song, Z.; Xiang, J.; Hu, S.; Su, S.; Sun, L. Chemical recycling of brominated flame retarded plastics from e-waste for clean fuels production: A review. Renew. Sustain. Energy Rev. 2016, 61, 433–450.
  8. Hasan, M.R.M.; Colbert, B.; You, Z.; Jamshidi, A.; Heiden, P.A.; Hamzah, M.O. A simple treatment of electronic-waste plastics to produce asphalt binder additives with improved properties. Constr. Build. Mater. 2016, 110, 79–88.
  9. Xu, F.; Zhao, Y.; Li, K. Using waste plastics as asphalt modifier: A review. Materials 2022, 15, 110.
  10. Solatifar, S.M.N. Optimized Preparation and High-Temperature Performance of Composite-Modified Asphalt Binder with CR and WEO. J. Mater. Civ. Eng. 2023, 35, 4022395.
  11. Jin, D.; Mohammadi, S.; Xin, K.; Yin, L.; You, Z. Laboratory performance and field demonstration of asphalt overlay with recycled rubber and tire fabric fiber. Constr. Build. Mater. 2024, 438, 136941.
  12. Jin, D.; Xin, K.; Yin, L.; Mohammadi, S.; Cetin, B.; You, Z. Performance of rubber modified asphalt mixture with tire-derived aggregate subgrade. Constr. Build. Mater. 2024, 449, 138261.
  13. Xu, X.; Leng, Z.; Lan, J.; Wang, W.; Yu, J.; Bai, Y.; Sreeram, A.; Hu, J. Sustainable Practice in Pavement Engineering through Value-Added Collective Recycling of Waste Plastic and Waste Tyre Rubber. Engineering 2021, 7, 857–867.
  14. Surya, M.; Bavithean, O.K.C.; Nandhagopal, A.R.; Snehasree, T. Stability study on eco-friendly flexible pavement using e-waste and hips. Int. J. Civ. Eng. Technol. 2017, 8, 956–965. Available online: http://iaeme.com/Home/issue/IJCIET?Volume=8&Issue=10http://iaeme.com (accessed on 10 December 2023).
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