Researchers propose eco-friendly pothole fix using unlikely material

18 Aug 2020

Image: © mbruxelle/

With potholes being the bane of many a road user, researchers have found a way to fix them using a common by-product of wastewater treatment.

Ireland is no stranger to potholes, some of which can fit a person in them, with estimates that 60pc of Irish drivers have damaged their car or bike as a result of hitting one. Typically, repairing potholes involves filling them with hydrocarbon-containing asphalt that can leach out and pollute the wider environment.

However, researchers set to present their findings at the latest virtual meeting of the American Chemical Society later today (18 August) have proposed a way to fix potholes in an eco-friendly way using the grit from wastewater treatment that is usually sent to landfill.

“We had an idea to divert wastewater grit from landfills and turn it into a marketable product,” said Zhongzhe Liu of California State University, Bakersfield. “We formulated it into a ceramic mortar that could be used as a patch for pothole repair.”

When wastewater is processed, clean water is released into waterways and the waste grit is collected. Unprocessed grit is heavy, non-biodegradable and made up from sewage, food scraps and other waste. Because it contains pathogens and impurities that make it unsuitable for direct recycling, it is usually taken to landfill and buried.

A side-by-side image of wastewater grit and the ceramic mortar material coloured white.

From left: Wastewater grit compared with the new ceramic mortar that can fill potholes. Image: Zhongzhe Liu

Lasts longer than asphalt

Taking this material, the researchers incorporated it into a chemically bonded phosphate ceramic (CBPC), routinely used to treat hazardous or radioactive waste for disposal. Until now, no one had used this on wastewater products.

Because CBPC contains ingredients that would inactivate microbes, the researchers thought this could be a good way to kill pathogens and end up with a material that could be safely applied to roads.

“In the first step of making a CBPC, we mix the wet grit with calcium oxide and magnesium oxide, which form an alkaline grit slurry that prevents the proliferation of pathogens,” Liu said.

“The second step is to add a weak acid, potassium dihydrogen phosphate, into the pathogen-minimised alkaline slurry to form the grit-CBPC mortar.”

This new substance, referred to as grit assisted patch (GAP), has been analysed in the lab showing it to have a comparable strength to asphalt but lasting longer. The researchers are now hoping to commercialise GAP, to conduct large-scale testing on an operational, busy road, and to test other additives to improve its durability.

Colm Gorey was a senior journalist with Silicon Republic