Eindhoven, Netherlands – A new air-purifying concrete applied as a road surface can reduce exhaust pollutants, according to researchers at the Eindhoven University of Technology in the Netherlands.

The material reduces the concentration of nitrogen oxides (NOx) by 25 to 45 per cent, said Professor Jos Brouwers.

The tests were carried out on a busy road that was resurfaced last fall. As part of the project, around 1,000 square metres of surface were covered with air-purifying concrete paving stones, and as a control, another area was surfaced with normal paving stones. Three air purity measurements showed that the area over the air-purifying concrete had a NOx content that was 25 to 45 per cent lower than the area paved with normal concrete.

“The air-purifying properties of the new paving stones had already been shown in the laboratory, but these results now show that they also work outdoors,” said Brouwers, who also said that further measurements are planned later this year.

The concrete contains titanium dioxide, a photocatalytic material that removes NOx from the air and converts it into harmless nitrate with the aid of sunlight. The nitrate is then rinsed away by rain. Since the stones also break down algae and dirt, they always stay clean.

The concrete stones used in the test are made by paving stone manufacturer Struyk Verwo Infra and are already available for use. For asphalt surfaces, the concrete can be mixed with open asphalt. It can also be used in building walls.

The stones themselves are 50 per cent more expensive than normal concrete stones, but the total road building costs are only ten per cent higher, Brouwers said.

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