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Tue 19 January 2021:

If you are a responsible citizen, you probably recycle your trash. You put your plastic waste into a special container so that it would be recycled into something new. However, most people don’t know that soft plastics, such as plastic bags, are very difficult to recycle and usually end up in landfills.

But what can be done about that? Scientists from the RMIT University and their industrial partners developed a special plastic aggregate for concrete.

It is not impossible to recycle soft plastics. It is just that because it is so flimsy, it requires a different process. And so it usually doesn’t end up being recycled. It would be better to use it as is – without washing and melting. But where?


Scientists and engineers developed a plastic aggregate, called Polyrok, for concrete. Concrete needs an aggregate filler, which improves its stability and adds desired characteristics. Usually gravel and sand are used, but those resources are also scarce and quarrying does damage the environment as well. Meanwhile Polyrok has multiple advantages over conventional aggregates and is generally a good way to recycle soft plastics.


First of all, it reduces plastic waste. A parking lot and a footpath in the City of Frankston have already been made using this plastic and it works great. It is estimated that 105,000 tonnes of soft plastics could be converted into Polyrok in one factory in Melbourne alone, which is a huge reduction of landfill waste. Polyrok also improves acoustic characteristics of concrete and is very light and easy to work with. It is just great and rather cheap. Although for now only 10 % of concrete is Polyrok, in the future the mixture could be improved.

Mixing plastic with concrete is not easy. Longer strands of plastics may trap air and those pockets can then be filled with water, which weakens the concrete. However, Polyrok granules are dense and they mix in with concrete very well. In the future scientists would like to use this plastic-enhanced concrete for 3D printing buildings. Although this study has been conducted in Australia, where 1.3 million pieces of soft plastic per day are returned to recycling bins, this method could be introduced in many countries around the world. Polyrok can reduce waste, while making concrete better suited for some applications.

Pollution needs to be addressed in many different ways. However, in order to really combat it you have to come up with something that brings economic benefits as well. Polyrok is relatively cheap, homogenous, has good sound absorption characteristics. Hopefully in the future more parking lots and other structures will be made from plastic-enhanced concrete.

Source: RMIT University




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