From the Eindhoven University of Technology. This is a neat idea that helps to solve a real pollution problem by automobiles. Cost of course is a factor, but considering some other schemes this may be a bargain. Now if they can just design some special cool asphalt for use around climate monitoring stations, we’ll really have something. – Anthony
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Road surfaces can make a big contribution to local air purity. This conclusion can be drawn from the first test results on a road surface of air purifying concrete. This material reduces the concentration of nitrogen oxides (NOx) by 25 to 45 per cent, said prof. Jos Brouwers in his inaugural lecture last Friday.
The tests were carried out in the municipality of Hengelo, where the busy Castorweg road was resurfaced last fall. As part of the project, around 1,000 square meters of the road’s surface were covered with air-purifying concrete paving stones. For comparison purposes, another area of 1.000 square meters was surfaced with normal paving stones.
Researchers at Eindhoven University of Technology (TU/e) carried out three air-purity measurements on the Castorweg last spring, at heights of between a half and one-and-a-half meters. Over the area paved with air-purifying concrete the NOx content was found to 25 to 45 per cent lower than that over 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 prof. Brouwers. Further measurements are planned later this year.
Asphalt
Brouwers, who has been professor of building materials in the TU/e Department of Architecture, Building and Planning since September 2009, sees numerous potential applications, especially at locations where the maximum permitted NOx concentrations are now exceeded. The concrete stones used in the tests are made by paving stone manufacturer Struyk Verwo Infra, and are already available for use. For roads where an asphalt surface is preferred the air-purifying concrete can be mixed with open asphalt, according to Brouwers. It can also be used in self-cleaning and air-purifying building walls.
The use of air-purifying concrete does not have a major impact on the cost of a road, Brouwers has calculated. Although the stones themselves are 50 per cent more expensive than normal concrete stones, the total road-building costs are only ten per cent higher.
Self-cleaning
Vehicle exhaust gases contain nitrogen oxides (NOx), which cause acid rain and smog. The air purifying concrete contains titanium dioxide, a photocatalytic material that removes the nitrogen oxides from the air and converts them with the aid of sunlight into harmless nitrate. The nitrate is then rinsed away by rain. These stones also have another advantage: they break down algae and dirt, so that they always stay clean.
Jos Brouwers, professor of building materials at Eindhoven University of Technology, delivered his inaugural lecture on the afternoon of Friday 2 July.
Can this stuff retread the tires as well?
Just asking.
Wow very cool stuff.
As for coolness, if you had an asphalt of high silica content, it would absorb heat and hold it, reconducting it into the ground, like a space shuttle tile. Pumice gravel would be a suitable substitute. Its thermal conductivity is 50 times less than crystalline quartz, so it absorbs heat and holds onto it for a long time. This would moderate night temperatures around a surface station but would prevent high daytime highs that could result from excessive reflection or rapid re-radiation of heat by a surface.
Ideally you would pack pumice gravel into a dense clay substrate which would give excellent load bearing and traction properties.
The 2x cost of the NOx paving stones can likely be reduced through mass production. Interesting science project. Uses experiments and measures stuff – what an idea!
Unless the surface can magically absorb CO2, not many will care. In Norway diesel powered cars have come very popular because the taxing system now favours them. The reason? Diesel cars emit less CO2, just about the only thing they emit less of. NOx, however, …
Sounds fantastic, but I’m concerned on what happens to the nitrates. Do they have any figures on the quantity of nitrates that would be produced? If, as I suspect, it’s lower than the run off from garden/farm fertilisation, then I think this is a great idea! In particular, I’d like to see it used in tunnels, where air quality can be a problem.
Best solution is dedicated bike trails. Second best is electric cars. It takes me just as long to drive to work as it takes me to ride, so I almost never drive – unless the roads are too icy.
I’m not buying any of that.
Automotive exhausts are hot, and therefore rise.
Any consequential ‘absorption’ which might take place would be incidental.
Oh, and another thing: NOx doesn’t cause so-called ‘acid rain.’ So that part of the story causes me no end of heartburn, and the intellectual ‘sniff test’ fails on that part for sure.
OT, but amusing ad was displayed:
Ads by Google
Rajendra Pachauri -Nobel Peace Prize Winner at The London Speaker Bureau
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Perhaps not quite their target audience 🙂
the total road-building costs are only ten per cent higher
Well then, much cheaper than Steven Chu’s brainstorm:
Surprised they didn’t mention that titanium dioxide is so pure snow white so it can raise the albedo too, combat some of the UHI.
As a lifelong summer barefooter in California, I can assure you that you can get great local cooling by painting the asphalt under the thermometers with the white striping paint used on roads.
Every single kid who was doing the Huck Fin thing through town would dash from paint stripe to paint stripe. You can simply walk or stand on the stripe, even when the black part is so hot you start doing the rain dance.
I’d love to set up a Stevenson Screen and MMTS somewhere, over both asphalt and grass, and document the differential. Then you could paint the asphalt white and repeat the test…
Amino Acids in Meteorites says: July 7, 2010 at 10:13 pm
“the total road-building costs are only ten per cent higher”
Well then, much cheaper than Steven Chu’s brainstorm:
Painting the
rosesroofs white might have the same effect as the paving stones. Now that they’ve outlawed lead, titanium dioxide is the main pigment in white paint. See, you don’t have to be as bright as Hillary to score big. You just have to be lucky.Nice to see that real science is alive and kicking and producing useful results.
Uh-huh.
What is the grip like in the wet?
899: time to rename, suggest 900. 😉
stevengoddard says:
July 7, 2010 at 9:56 pm
“Best solution is dedicated bike trails.[…]”
Unfortunately that potential has largely been depleted in Europe already so we will have to pay for this special “makes roads only 10% more expensive so it doesn’t really hurt, especially when we make the evil car owners pay for it by incrasing fuel tax” concrete. Can one step barefoot on that concrete on a sunny day without being absorbed catalitically?
BTW, this study sounds a lot like the maker of the stones paid for it. You have a new product, you pay a research institute to do some tests on it and you or the people from the institute get the opportunity to exploit the measured data from the test in some papers.
Do the three-way catalytic convertors that have been required on all U.S. autmobiles manufactured after 1981 somehow not work if they were required on cars in other countries?
/sarc off
As an alumnus from TU/e I am delighted to see a good idea put into practice, measurements being planned and executed, a reference being built into the experiment. It is likely that computer simulations were used in the design of the asphalt but using good engineering practices the performance has been confirmed through experiment. If only global warming science would adhere to these basics.
Titanium dioxide dust (see: http://en.wikipedia.org/wiki/Titanium_dioxide#Health_and_safety) may be carcinogenic if inhaled. I would be interested to learn if the study has included possible the effects on health.
“…titanium dioxide, a photocatalytic material that removes the nitrogen oxides from the air and converts them with the aid of sunlight into harmless nitrate. The nitrate is then rinsed away by rain.”
So what about the impact on nitrate concentrations in surface water (>groundwater quality)? In recent years, many countries (all of the EU member states) have issued regulations to prevent nitrates from agricultural sources polluting ground and surface waters … So now that the farmers have invested in all kinds of techniques to get their nitrates down, let others go ahead and “pollute”.
Yes I know, nitrogen oxdes are more harmful than nitrates, but still, I can imagine how those conscientious farmers will feel.
Anthony,
Having a rough time with this story.
People actually tested this in a laboratory before testing again in the field?
No computer model?
Real measurements, with predicted values compared to actual?
I guess there are still some real scientists out there.
Amino Acids in Meteorites says:
July 7, 2010 at 10:13 pm
Thank you Amino. Very funny.
I’ve been referring to wind turbine as bird grinders. Now I can start referring to Choo Choo.
Painting asphalt roofs with titanium dioxide pigments may create other problems since asphalt shingles need to absorb UV light to avoid moisture under the shingles (rotting roofs) and to extend the shingle’s life since the heat helps keep the shingle from becoming too brittle and degrading. A metal roof might be the best overall since it can be coated, has a very long life and sound really cool when it rains. Maybe with enough nuclear power plants we could just melt all our old metal and make metal roof panels/shingles. One still needs energy and as cheaply as possible.
I agree with Steven Goddard on this one: “Best solution is dedicated bike trails. Second best is electric cars.”
How about if we spend the extra 10% on those two solutions (which will also help with other problems) rather than this one?
They could build all roads so they only drive downhill. Save on fuel.
As long as we have fear, we will see urgency in funding crazy notion research.