Article

How to use glass waste as a sustainable alternative to sand in construction


Glass waste can be a great sustainable alternative building material to natural sands in various construction applications (credit: noomcpk on Shutterstock)
Glass waste can be a great sustainable alternative building material to natural sands in various construction applications (credit: noomcpk on Shutterstock)

Of key current concern is that we are using earthen materials more quickly than they can be replenished. This is why Earth Overshoot Day is now observed every year! Earth Overshoot Day is the date on which we have used all earthly resources available for that year. In 2022, it already fell on 28 July, which means we were close to using twice as much earthen materials as were available.
Currently, the sector that uses the most earthen resources is the construction sector. This sector uses, for example, much stone, gravel, and sand. Construction sand is usually taken from beaches, quarries, and riverbeds. It is estimated that between 32 and 50 billion tonnes of sand and gravel are used globally every year! This is between 5,500 and 8,700 Great Pyramids of Giza! And what makes it worse: the use is expected to increase by 5% per year.
As sand is a limited natural resource, it is unsustainable to continue using it at the current rate. That is why it is important to develop more sustainable approaches in construction. The following video nicely elaborates on this point (4:47–7:12):
https://youtu.be/bVaf5kyO6Ts


One approach is using self-healing concrete. Another way is using waste materials in place of natural sources, such as crushed waste glass. This helps solve two pressing challenges at the same time: sand depletion and reducing the ever-increasing amount of waste glass ending up in landfills. 
Using waste materials also helps the transition into a circular economy. A circular economy is an economy in which products are used as long as possible by sharing, reusing, repairing, and refurbishing them, and at the end of their life use their materials for new products. Transitioning to this economy is essential to ensure that we also have enough earthen resources available for the expected world population of nearly 10 billion by 2050. 
This is why crushed waste glass is a great, sustainable alternative to sand:
Crushed waste glass could replace natural sand in geotechnical construction applications (credit: Dr Danish Kazmi, published with permission)
Crushed waste glass could replace natural sand in geotechnical construction applications (credit: Dr Danish Kazmi, published with permission)


Characteristics

The first reason why crushed waste glass can be a great, sustainable alternative to natural sand is because of the similar engineering characteristics. For example, the chemical composition of both sand and crushed waste glass is similar as both largely consist of silica. This is because glass is produced by melting sand. Likewise, the densities achieved by traditional sand and crushed waste glass particles are similar. Density means how tightly particles can be packed together.
While sand and crushed waste glass have certain characteristics in common, they also differ. For example, beach sand particles are typically more rounded than crushed waste glass particles. Their more angular shape makes these particles interlock more easily, which increases strength. Also, waste glass can be crushed to varying particle sizes. This is important because engineering characteristics of building materials differ with different particle sizes.
Natural beach sand (left) and crushed waste glass (right) have different particle shapes, with glass particles often being more angular than natural beach sand particles; credit: Dr Danish Kazmi, published with permission)
Natural beach sand (left) and crushed waste glass (right) have different particle shapes, with glass particles often being more angular than natural beach sand particles; credit: Dr Danish Kazmi, published with permission)


Performance

The second reason why crushed waste glass can be a great, sustainable alternative to natural sand is because of its similar or improved engineering performance. Depending on various parameters, the engineering behavior of crushed waste glass can be similar, or sometimes even superior, to that of natural sand. For example, the strength of both materials is similar when the particles are dry. But interestingly, the strength of crushed waste glass is higher when the particles are submerged in water. This may be because the water and glass particles attract each other.
Also, crushed waste glass performs better than natural sand with respect to abrasion and permeability. This means that glass particles wear away less quickly and allow water to pass through pores more easily. The higher permeability may be because of the non-porous and smooth surfaces of the glass particles, facilitating the flow of water. 

Example application

Because of the similar or improved engineering characteristics and performance of crushed waste glass, it can be used in a wide range of applications. One of these applications is in granular columns to strengthen weak soils such as clay. Granular columns are vertical boreholes created in the ground and filled with compacted granular materials (such as sand, gravel, or crushed stone) that are stiffer than the original soil. These columns make the weak soil relatively stronger and denser. They also help drain water from the soil. This increases strength, the downward vertical movement (settlement), and helps reduce damage caused by earthquakes. Together, this supports the stability of the overlying infrastructure.

Granular columns make weak soil stronger (© Dr. Erlijn van Genuchten)
Granular columns make weak soil stronger (© Dr. Erlijn van Genuchten)

This is also clearly explained and shown in an animation in this video (5:21–5:54):


Typically, sand and stone are used as granular materials to fill these columns. But crushed waste glass could also be used and may be even better suited because glass particles are stiffer than sand particles.
One issue with granular columns is that they are likely to bulge when they carry a heavy load. Bulging means that the diameter of the column widens. This could weaken the column and make water drainage less effective. Also, it may cause the surrounding soil to enter the granular column and reduce its stability. This problem can, for example, be resolved by encasing the granular column in a special geotextile that helps keep the particles in place and the column intact.

Conclusion and how we can take action

So, crushed waste glass can be a great alternative to natural sand in many construction applications because its relevant engineering characteristics and performance are similar, or sometimes superior, to that of traditional sands. It can, for example, be used in granular columns to strengthen weak soils and make these soils suitable for construction.
Here are practical ideas about what you and I can do to support glass waste being used in construction:
  • Depositing glass waste to designated bins,
  • Discussing with construction companies, consultants and regulators the potential use of crushed waste glass as an alternative to natural sand in construction,
  • Using crushed waste glass instead of natural sand for different building applications, such as tiles and bricks,
  • Becoming a responsible consumer in general by changing mindsets, and
  • Supporting activities and research promoting the transition to a circular economy
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Did you enjoy this article? Then I’m sure you’ll love my book “A Guide to A Healthier Planet” as well. Have a peek inside the book at:


About the author Dr. Erlijn van Genuchten is a an internationally recognized environmental sustainability expert. She is a science communicator, helping scientists in the fields of nature and sustainability increase the outreach of their results and allowing us all to put scientific insights into practice and contribute to a sustainable future. Erlijn has inspired thousands of people around the world  — for example — by supporting the United Nations with her expertise, her book “A Guide to A Healthier Planet” published by Springer Nature, her YouTube channel Xplore Nature, and her posts on social media.



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Additional material

In this video, the scientists who performed this research provide a clear overview of the importance of research like this and why desert sand is unsuitable for construction:


In this picture and video, you can see how the experiments were conducted (3:16–3:42):
An experiment is being set up to investigate the feasibility of using crushed waste glass in backfilling granular columns (credit: Dr Danish Kazmi, published with permission)
An experiment is being set up to investigate the feasibility of using crushed waste glass in backfilling granular columns (credit: Dr Danish Kazmi, published with permission)




In this video, the sand and glass particle characteristics in granular columns are explained in more detail:


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Credit
This article is based on:
Kazmi, D., Serati, M., Williams, D. J., Qasim, S., & Cheng, Y. P. (2021). The potential use of crushed waste glass as a sustainable alternative to natural and manufactured sand in geotechnical applications. Journal of Cleaner Production, 284, 124762.
Kazmi, D., Serati, M., Williams, D. J., Olaya, S. Q., Qasim, S., Cheng, Y. P., & Carraro, J. A. H. (2022). Kaolin clay reinforced with a granular column containing crushed waste glass or traditional construction sands. International Journal of Geomechanics, 22(4), 04022030.
Connect with the scientists through LinkedIn or UQ Researchers Page.
  • George Kariuki

    2 w

    This is brilliant! Using crushed glass as an alternative to sand is a fantastic sustainable solution. Love the idea of a circular economy where we reuse and repurpose materials!

    4
    • Sarah Chabane

      2 w

      Super interesting! I remember learning that we will run out of sand quite soon, so we need alternatives!

      2
      • Saustine Lusanzu

        2 w

        We want to reduce massive plastic pollution, this is a good project for the earth sustainability

        7
        • walter lungayi

          2 w

          This is a commendable practice that helps reduce environmental impact. By recycling glass into construction materials, we can decrease the demand for natural resources like sand while diverting waste from landfills, promoting a more circular economy.

          8
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