The concrete these Dutch researches have created is coated with titanium dioxide, stuff that's already being used in paint for it's 'self-cleaning' properties (dirt does not attach to it). It has the additional property being 'photocatalytic'; converting nitrogen oxides into nitrate using sunlight. Nitrate is easily 'cleaned' by rain as it's soluble in water.
The concrete these researchers developed has actually already shown promising results in real world tests. The potential applications of the stuff are broad: it could be mixed with asphalt for roads, used for pavements in tiles and even to build walls with. That sounds like just about all you need to build a modern-day city :).
Incorporating the addition of titanium dioxide to concrete's production cycle is supposedly not very complicated. Next to that, the stuff is very durable; it does not need any extra maintenance (it even cleans itself ;)) and doesn't wear off. It is a tad more expensive, but the payback is evident. Until the electric future is upon us, this sounds like a very good way to cut back on air pollution.
» Photo by romainguy