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US team uses composite waste to strengthen permeable pavement

With urban flooding on the increase around the world, planners are making increasing use of permeable pavements that allow water to drain away, thereby controlling storm-water run-off.

Indeed, here in the UK, permeable paving accounts for an increasingly high proportion of all new paving that’s installed.

permeable pavement
Water runs through Washington State University's pervious pavement

However, because permeable paving is highly porous, it’s not as durable as the traditional concrete that is used on major roads and can therefore be more expensive to maintain.

In response, a team of researchers at Washington State University have demonstrated that the strength of permeable pavements could be significantly improved through the addition of waste carbon fibre composite material.

Famed for their lightweight and strength, Carbon fibre composites are used widely across a range of industries, and with the market growing at around 10 per cent per year, and with industries struggling to easily recycle their waste, composite scrap is an abundant, and relatively untapped resource.

The Washington team’s recycling method, described in the March issue of the Journal of Materials in Civil Engineering, involved adding carbon fibre composite scrap supplied by Boeing to their pervious concrete mix. The added material greatly increased both the durability and strength of pervious concrete.

The group used mechanical milling techniques to refine the composite pieces which were then dispersed throughout the pavement mix to provide uniform strength.

"In terms of bending strength, we got really good results - as high as traditional concrete, and it still drains really quickly," said one of the project leaders Somayeh Nassiri, an assistant professor in the Department of Civil and Environmental Engineering.

Whilst the researchers have shown that the material works at the laboratory scale, they are now beginning to conduct real-world tests on pavement applications and also working with industry to begin developing a supply chain.

"In the lab this works to increase permeable pavement's durability and strength," said Nassiri, "The next step is to find out how to make it mainstream and widespread.