Waste Plastics can Improve the Performance of Soil !

Some of the soil types found in nature are listed below:

• Sandy soil: Contains small particles of weathered rock, as it’s formed by disintegration of granite, limestone and quartz type of rocks.
• Silt Soil: Contains smaller particles compared to the sandy soil, and is more fertile compared to other soil types.
• Clay Soil: Contains particles of smallest size which are tightly packed together with each other. It is the densest and heaviest type of soil which is difficult to drain and hardly provides space for flourishment of plant roots.
• Loamy Soil: This is a combination of above three soil types, and is most suitable for farming.

There may be other classifications and nomenclatures involved, but above is one of the common types of soil classification. Can you comment about other soil classifications and their names?

Of the types of soils classified above, clay soils are very important in applications such as geology and construction attributed to their impermeability and containment barrier ability; wherein, knowledge of swelling characteristics namely swelling pressure, swelling potential and swelling index is important to be understood and be optimal. As per studies this soil deforms on cyclical drying and wetting limiting their usage in construction of building foundations, drainage channels, buffers in radioactive waste disposals, etc.

In order to overcome problems, usage of natural reinforcing agents such as twigs, grass, leaves etc. was first suggested by Vidal in 1969 improving soils stability and shear resistance. However, recently several research works have reported usage of waste plastic in place of the natural reinforcing agents, which are not only non-biodegradable, long lasting, but also available in humungous amounts through various sources.

Some of the recent research studies in the field are mentioned below:

• Alvarex et al., utilized 3-5 mm length crushed recycled polyethylene terephthalate (PET) as a reinforcing material to stabilize and improve the mechanical properties of the high plasticity clay soil, and found optimal performance improvement at 1% addition.
• Yarbasi et al., investigated the effect of addition of waste PET fiber as reinforcing agent in clayey soils for being suitable to be used in geotechnical applications; which were tested for mechanical and freeze-thaw resistance, and determined maximum strength values when added with 0.3 % waste PET fiber and cured for 28 days.
• Salazar et al., determined that addition of 20% crushed PET optimally improved the soil performance and can be positively used in geotechnical works.
• Louzada and Casagrande prepared PET flakes reinforced soil and found that 3 and 5% addition of it significantly improved the friction angle and cohesion of soil-PET mixtures.
• Researchers namely Taha et al. even investigated the usage of polypropylene fibers as soil reinforcing agents with best improvements obtained at 3% addition.

These are some interesting studies, wherein plastics are projected as soil improvers rather than its usual image as spoilers. However, some questions which can still pop up could be:

• Can the additives in the plastics leach out and affect the soils performance in long term?
• What will be done with this reinforced soil after its intended period of usage, as this soil still contains waste plastic?
• Can the plastic affect the biological life nearby?
• Which applications are more suitable and which are not preferable with this approach of soil reinforcement?
• How much will the cost of this soil be compared to non-reinforced soils, as here one has to cut waste plastic to a defined size, weighed to a defined quantity and mixed using an equipment requiring electricity which would also require appropriate work area and manpower? Will it be sustainable for commercialization or will remain an academic research?

There could be many other questions, but one thing is certain, there is a way to utilize waste plastic in a non-conventional way which is rather interesting.

Dear Readers, do go through the above literature and let me know your viewpoints in the Comments section.

Thanks for reading!

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References:

• Alvarez, A., et al. “Improved mechanical properties of a high plasticity clay soil by adding recycled PET.” MS&E 758.1 (2020): 012075.
• YARBAŞI, Necmi, and Ekrem Kalkan. “The mechanical performance of clayey soils reinforced with waste PET fibers.” International Journal of Earth Sciences Knowledge and Applications 2.1 (2020): 19-26.
• Salazar, Leo Astorayme, Franco Ramón Díaz, and Gary Durán Ramírez. “Shear strength of a reinforced clayey soil with crushed polyethylene terephthalate.” 2019 Congreso Internacional de Innovación y Tendencias en Ingenieria (CONIITI). IEEE, 2019.
• Taha, Mazahir MM, Cheng Pei Feng, and Sara HS Ahmed. “Influence of Polypropylene Fibre (PF) Reinforcement on Mechanical Properties of Clay Soil.” Advances in Polymer Technology 2020 (2020).
• Gunaydin, Osman, et al. “CHARACTERISTICS OF SOILS IMPROVED WITH POLYETHYLENE TEREPHTHALATE WASTES.” Environmental Engineering & Management Journal (EEMJ) 18.2 (2019).
• Louzada, Nathalia dos Santos Lopes, José Adriano Cardoso Malko, and Michéle Dal Toé Casagrande. “Behavior of Clayey Soil Reinforced with Polyethylene Terephthalate.” Journal of Materials in Civil Engineering 31.10 (2019): 04019218.
• Louzada, N. S. L., and M. D. T. Casagrande. “Study of the Mechanical Behavior of a Clayey Soil with the Insertion of Polyethylene Terephthalate Flakes.” Geo-Chicago 2016. 2016. 885-892.
• Biradar, S. V., and Md Khaja Moniuddin. “Soil Stabilization using Waste Pet Fiber Material.”

• https://byjus.com/biology/types-of-soil/
• https://www.thespruce.com/understanding-and-improving-clay-soil-2539857
• https://www.fnp.com/blog/different-types-of-plant-soils-in-india
• https://isequalto.com/iet-app/ask-the-world/OVdi4185-how-is-clayey-soil-useful-for-crops?