Asphalt Gets a Hot, Green Makeover

money talks b/s walks sometimes hindsite still isnt 20/20

Green asphalt? The fact is that the aromatic hydrocarbons in asphalt, (including polyaromatic hydrocarbons) have been proven carcinogens. There's nothing green about taking the sludge with the leftovers from the refinery and making a road out of it. Furthermore, we seal driveways and parking lots with a thick layer of coal-based sealant, which has even more toxic hydrocarbons. The water from roads flows into the drinking water supply systems downstream. If it causes cancer in mice, how is it "Green"? Come on PopSci, you're supposed to present reality as we know it through science, not as people spin it for their own financial gain.

It is just not feasible to continually use our dwindling supplies of petroleum to create short-lived roads. We need steel rails, which are non-toxic and long-lived, to move people and goods across long distances, and within towns. Bricks, concrete, and gravel are also good green long-term investments, but tearing up toxic roads and replacing them using slightly less polluting technologies is never going to be a viable solution to our economic and environmental problems.

EParker - While no asphalt is "green," certainly you have no qualms with existing processes becoming "greener" by not being as bad as they were.

Clearly, we are not going to stop paving roads any time soon, so the cleaner that process is, the beter.

I perfer a dollar to a dime, but I will still bend over to pick up a dime (most profitable 3 seconds of my day).

Oakspar-
Calling this technology "greener" is like putting ointment on a bleeding leg which really needs a tourniquet, and claiming to have "helped" the situation. It's a pure distraction from the real issue of how we create a transportation system that is viable in the long run, and fools the general public into thinking everything is going to be OK, and that serious overhaul isn't needed.

In fact, we already HAVE begun to cut road paving sharply, due in part to rising asphalt prices:
http://www.nytimes.com/2008/06/29/nyregion/nyregionspecial2/29Rasphalt.html?n=Top/Reference/Times%20Topics/Sub...

I know the roads near my house are degrading faster than they are being repaired, and the declining economy is only adding to the pain. Even if this process is slightly less expensive, it will still require millions of dollars to pave each mile of highway. Never mind Jevon's paradox, which states that this technology will actually INCREASE the total amount of asphalt used, by lowering the incremental cost. See http://en.wikipedia.org/wiki/Jevons_paradox

The question is, do we continue to pump our limited capital into rapidly degrading, increasingly expensive and toxic roads, or do we take a longer view and shift that funding into light and high-speed rail systems that will endure for centuries? We used to have the best rail system on the planet, and now we're well behind the Europeans and Japanese because we continue to believe that cheap pavement will solve all of our transportation problems.

One question, Why is the picture of a Concrete Truck when the article is about Asphalt.....Carolyn, do you know the difference? (besides color)

Ooops thought of a 2nd question, What is the most Recycled building material in the US?.........That's right, Asphalt...nothing else even comes close...

Warm mix sounds like a good idea, but I'd like to see it tested in a Cold climate. We have enuf pot holes in MN and a large amount of them are because the mix was not put down hot enuf....they're usually where there are seems and where they "Quit for the day"...

The comment from EParker is not accurate. Asphalt is actually an environmenatally sustainable material -- i.e., very green.

First - because it is America's most recycled material. Around 100 million tons of reclaimed asphalt pavement is used every year. This doesn't include all the materials from other industries (such as crumb rubber from tires) that are incorporated into asphalt pavement. With future technology, we may be able to build roads from 100 percent recycled material, so there would be no mining of aggregates and no extraction of crude oil.

Second - because asphalt has by far the lowest carbon footprint of any pavement material. The industry is reducing the carbon footprint even further by using new warm-mix asphalt technologies. These are different from the cold mixes that are used for pothole patching. They have been used in every climate and region of the U.S. and performance looks excellent.

Third - because porous asphalt pavements all over the country are improving water quality.

Fourth - asphalt pavements can be perpetual. They are built to last indefinitely, and the only maintenance needed is "mill and fill" - remove the surface for recycling, and replace it with an overlay that is smooth, quiet, safe, and durable

As to coal tar sealants -- coal tar is not asphalt, and asphalt pavements do not need to be sealed with coal tar. Let asphalt be asphalt!

Here's an idea - what about building in heat sinks underneath the asphalt that collect heat on hot summer days and then transfer that heat into electrical energy?

I'm sure this is a crazy idea, but if there were a way to do it, it's another way of generating electricity without using fossil fuels. :-)

I like hypnometal's idea. Heat from the sun warms blacktop in some areas of the country so hot that you can fry an egg on it. If pipes or hoses were embedded into the asphalt (this might be a bit costly, but it could be worth it, maybe), water could be run through them and heated. Though there isn't enough heat to boil the water, the heat difference between the hot water and the air could be used in a stirling engine. Water would, after flowing through the pipes, enter a chamber attached to the engine and then exit again, cold, and would re-enter the pipe system. The engine would cool itself with a radiator. Stirling engines work by slight temperature differences (I've seen one in a catalog that can run off the heat from a person's hand), so it could be viable. The heat could also be used to heat water in water heaters or pools to reduce natural gas consumption.

This is a photo of a concrete truck not a cement truck.
Cement is an ingredient in concrete along with aggregates, sand other additives,i.e. set retarder and water