Crushed wine bottles and other recycled glass could replace sand in vital tunnelling supports, cutting construction costs and improving the sustainability of sand mining.
University of Queensland engineers are working on the second phase of an industry-sponsored project using crushed waste glass (CWG) to replace sand in shotcrete used to support tunnels and underground spaces.
Dr Mehdi Serati from UQ’s School of Civil Engineering said the amount of sand in the world is finite, so ingenuity is necessary to solve the problem of a looming shortage.
“Over the past 20 years the cost of sand has increased by six times, and it’s the second most consumed natural product globally, after freshwater,” Dr Serati said.
CWG is made up of recycled glass from wine bottles and other products, which are usually stockpiled or sent overseas for other countries to process and store as waste.
Dr Serati said CWG has a number of advantages as a potential replacement for sand.
“It’s a cheaper product because it’s using waste from one industry and turning it into treasure for another,” he shared.
“It also uses less water, as glass has zero water absorption, so really there is a triple benefit in terms of conservation, cost and saving water.”
Results are positive after one year of testing and Dr Serati said the next phase of the project could be to manage the combinations of recycled glass and other ingredients to optimise shotcrete for CWG rather than for sand.
“And it’s timely because we’re right at the start of a tunnelling boom in Australia,” he said.
“I think by 2030, five or six out of ten infrastructure projects in Australia will be either directly or indirectly linked to tunnelling.”
Niki Jackson from GCP Applied Technologies said the project is very promising.
Photography credit: Glenn Hunt. Image courtesy of the University of Queensland.
“The results so far show that using CWG as a replacement for natural sand is a viable option as the concrete was able to meet and sometimes exceed the results from the base mix,” Mr Jackson said.
“This would allow the industry to look at alternative options for replacing natural sands with a viable solution, in that CWG can be used in shotcrete for tunnels and civil works.”
“There would need to be a further study carried out on the fire resistance of concrete containing CWG for the shotcrete to be able to be used in all aspects of the civil tunnel environment.”
UQ Adjunct Professor and Aurecon’s Dr Harry Asche said the results so far were exciting, and confirmed a significant opportunity in concrete and shotcrete technology.
“Replacing sand with recycled glass is a great opportunity to improve sustainability in tunnelling,” Dr Asche said.
“One of the exciting things about this technology is that it could be implemented on major projects very soon.”
The idea for this project came from UQ research using CWG to strengthen soil in the construction industry. Industry and individual support from Dr Harry Asche (Aurecon), Niki Jackson of GCP Applied Technologies (Sydney, Australia), and Enviro Sand has allowed the project’s extension.
