"The municipality of Hengelo and the University of Twente (UT) are paving a test road section in Hengelo with air-purifying stones. The top layer of the concrete stones converts nitrogen oxide from exhaust fumes into harmless nitrates," says the university.
The top layer of the paving stones is made of air-purifying concrete. This concrete contains titanium dioxide, a photocatalytic material which uses sunlight to convert the nitrogen oxides in the air into harmless nitrates. The rain then washes the streets clean.
