Engineers have discovered a way to replace all of the conventional aggregates in concrete with rubber from discarded tyres.

A team from RMIT University says the new greener and lighter concrete meets building codes and could reduce manufacturing and transportation costs significantly.

Small amounts of rubber particles from tyres are already used to replace these concrete aggregates, but efforts to replace all of the aggregates with rubber have produced weak concrete that failed to meet the required standards – until now.

The RMIT team has come up with a manufacturing process for structural lightweight concrete where the traditional coarse aggregates in the mix are completely replaced by rubber from used car tyres.

“We have demonstrated with our precise casting method that this decades-old perceived limitation on using large amounts of coarse rubber particles in concrete can now be overcome,” says RMIT lead author Mohammad Momeen Ul Islam.

“The technique involves using newly designed casting moulds to compress the coarse rubber aggregate in fresh concrete that enhances the building material’s performance.”

Research team leader, Professor Jie Li, says this manufacturing process will unlock environmental and economic benefits.

“As a major portion of typical concrete is coarse aggregate, replacing all of this with used tyre rubber can significantly reduce the consumption of natural resources and also address the major environmental challenge of what to do with used tyres,” he said.

Used tyres in Australia cannot be exported, making new methods for recycling and reprocessing them locally increasingly important. About 1.2 billion waste tyres will be disposed of annually worldwide by 2030.

The greener and lighter concrete could also greatly reduce manufacturing and transportation costs, Dr Li said.

“This would benefit a range of developments including low-cost housing projects in rural and remote parts of Australia and other countries around the world.”

The team’s manufacturing process could be scaled up cost effectively within a precast concrete industrial setting in Australia and overseas, Mr Islam said.

Following successful testing in the workshop, the team is now looking into reinforcing the concrete to see how it can work in structural elements.

More details are accessible here.