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Waste glass a superior alternative for ground improvement

PhD candidate Danish Kazmi is investigating the geotechnical performance of ground improvement columns made entirely from crushed waste glass and comparing this with the traditional use of sand. The columns are designed to strengthen the ground many metres below buildings and improve their load-bearing characteristics.

{{quote-A:R-W:175-I:2-Q:“The use of crushed waste glass as an alternative to traditional sand would also reduce the demand for finite and expensive sources of traditional sand” -who:Danish Kazmi, University of Queensland}}It is estimated Australians consume more than 850,000 tonnes of glass each year, of which 60 per cent remains unrecycled and accumulating in stockpiles. Its disposal has become a worsening environmental challenge due to its limited end uses and non-biodegradable nature.

“The use of crushed waste glass in ground improvement columns could potentially consume much of the increasing stockpile of waste glass, as the demand for development on poor ground close to cities increases and the scarcity and cost of traditional sand continues to increase,” Kazmi said.

“The use of crushed waste glass as an alternative to traditional sand would also reduce the demand for finite and expensive sources of traditional sand.”

Higher permeability, abrasion resistance

According to Kazmi, both sand and waste glass possess a similar chemical composition, meaning they are expected to behave similarly when optimally used in geotechnical construction.

His research has broadly consisted of two stages. First, he analysed the characteristics and geotechnical parameters of crushed waste glass and compared them with traditional natural and crushed sand.

In that study, Kazmi found the permeability and abrasion resistance of crushed waste glass was relatively higher compared with the other two sands. Altogether, the results indicated crushed waste glass could be a potential alternative to traditional sands in geotechnical applications.

Building on those findings, Kazmi’s latest research is investigating the behaviour of both sand and waste glass columns in a weak soil for ground improvement.

“Crushed waste glass outperformed traditional sand in tests, which strengthens my hypothesis that it can potentially be used in ground improvement columns offering similar, or even superior, geotechnical performance to traditional sand columns.”

{{image3-a:r-w:275}}Kazmi said that while crushed waste glass has previously been studied in other civil engineering applications, he is among the first to investigate its use in ground improvement columns. He plans to study the behaviour of crushed waste glass at different particle size ranges.

“In concrete, the use of crushed waste glass may lead to a reduction in concrete workability, and the impurities attached to crushed waste glass may impact the performance of concrete. Therefore, crushed waste glass may only partially replace traditional sands in a concrete mix,” he said.

“I believe that crushed waste glass offers more potential to replace traditional sands in ground improvement columns since it has similar or improved geotechnical behaviour. Based on my current knowledge, I believe the particle size and shape, gradation, and shear strength of crushed waste glass support its use in ground improvement columns.”

Kazmi is currently a PhD candidate in the Geotechnical Engineering Centre in the University of Queensland’s School of Civil Engineering and guided by PhD advisors Professor David Williams and Dr Mehdi Serati.


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