Waste ash from coal could save billions in repairing US bridges and roads

March 29, 2011

Coating concrete destined to rebuild America's crumbling bridges and roadways with some of the millions of tons of ash left over from burning coal could extend the life of those structures by decades, saving billions of dollars of taxpayer money, scientists reported here today at the 241st National Meeting & Exposition of the American Chemical Society. They reported on a new coating material for concrete made from flyash that is hundreds of times more durable than existing coatings and costs only half as much.

Study leader Charles Carraher, Ph.D., explained that the more than 450 coal-burning electric power plants in the United States produce about 130 million tons of "flyash" each year. Before air pollution laws, those fine particles of soot and dust flew up smokestacks and into the air. Power plants now collect the .

"Flyash poses enormous waste disposal problems," Carraher said. "Some of it does get recycled and reused. But almost 70 percent winds up in landfills every year, where space is increasingly scarce and expensive. Our research indicates that this waste could become a valuable resource as a shield-like coating to keep from deteriorating and crumbling as it ages."

Carraher, who is with Florida Atlantic University, said that the new material can be used to coat and protect from corrosion steel reinforcing bar, or "rebar," rods embedded in concrete to reinforce and strengthen it. The coating also is suitable for repairing damaged concrete. This is part of a joint project between industry (Felix Achille, of Blue World Crete) and academia (Charles E. Carraher, Ph.D., Dept. of Chemistry and Biochemistry; Madasamy Arockiasamy, Ph.D., Dept. of Civil Engineering; and Perambur Neelakantaswamy, Ph.D., Dept. Electrical Engineering and Computer Science).

Laboratory tests have shown that the coating has excellent strength and durability when exposed to heat, cold, rain, and other simulated environmental conditions harsher than any that would occur in the real world, Carraher said. The coating protected concrete from deterioration, for instance, that involved exposure to the acids in air pollution that were 100,000 times more concentrated than typical outdoor levels environment. Coated concrete remained strong and intact for more than a year of observation, while ordinary concrete often began to crumble within days, he said.

Carraher cited U.S. Environmental Protection Agency estimates for the cost for repair, restoration, and replacement of concrete in domestic wastewater and drinking water systems. They range up to $1.3 trillion, and by some accounts must be completed by 2020 to avoid environmental and public health crisis problems. Crumbling concrete roads and bridges will require hundreds of billions more.

Use of the could extend the lifespan of those structures, with enormous savings, while helping to solve the flyash disposal problem, Carraher noted.

Explore further: 'Pollution' may be key ingredient in concrete mixtures, researcher says

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5 / 5 (3) Mar 29, 2011
Wasn't there this whole issue with fly ash containing dangerous levels of arsenic, chromium, mercury...? I wonder how they're going to handle all that.
not rated yet Mar 29, 2011
Yeah i was wondering the same. If anything, coal ash will be a trade off in strengthening our infrastructure it seems.
4 / 5 (4) Mar 29, 2011
Don't forget about radioactive materials in the coal ash.
5 / 5 (2) Mar 29, 2011
The rest of the world uses pulverised fuel ash (PFA) regularly as a replacement for some of the cement in concrete. It not only uses up a cheap waste product but also adds useful properties and durability to the concrete. Plus it has been shown to reduce CO2 emissions by 17% when replacing 30% of the cement. In the USA and to some extent the UK however, they've classified it as a hazardous waste product because there was a landslide in a big pile of it once!
Environmental agencies need to get their acts together and promote reuse of waste products.
not rated yet Mar 29, 2011
Extract from CIA/DETR report:
DEFINING & IMPROVING ENVIRONMENTAL PERFORMANCE IN THE CONCRETE INDUSTRY, Effects of ground granulated blastfurnace slag and pulverised-fuel ash upon the environmental impacts of concrete, D HIGGINS, L PARROTT & L SEAR, JANUARY 2000
For strength equivalence at 28-days, 50% ggbs or 30% pfa replacement, produced clear reductions of environmental impact:
· 'greenhouse gas' emissions reduced by 40% with the ggbs replacement, and 17% with pfa,
· 'acidification' reduced by 34% with the ggbs replacement, and 15% with pfa,
· 'winter smog' reduced by 34% with the ggbs replacement, and 15% with pfa,
· 'eutrophication' reduced by 32% with the ggbs replacement, and 13% with pfa,
· 'primary energy' requirements reduced by 29% with the ggbs replacement, and 14% with pfa,
Mineral extraction is dominated by the effects of the aggregates and smaller impacts were apparent (a reduction of 8% with ggbs and 4% with pfa).
not rated yet Mar 29, 2011
CIA/DETR project showed that using 30% PFA for equal 28 day strength in a concrete mix that:
Greenhouse gas emissions are reduced by 17%
Acidification reduced by 15%.
Winter smog reduced by 15%.
Eutrophication reduced by 13% .
Primary energy requirements reduced by 14%.
not rated yet Mar 29, 2011
Just curious if gasification of coal would create fly ash?
5 / 5 (3) Mar 29, 2011
Can we rebuild America using something other than coal?
5 / 5 (2) Mar 29, 2011
Another effort to "socialize risk" and a profit vector for Big Coal at the expense of the public purse. Without some life-cycle testing to determine public and environmental health risks, it would be the height of irresponsible idiocy to go forward with this.
not rated yet Mar 29, 2011
Another effort to "socialize risk" and a profit vector for Big Coal at the expense of the public purse. Without some life-cycle testing to determine public and environmental health risks, it would be the height of irresponsible idiocy to go forward with this.

Say public health to any EPA official and watch them whine and tilt their head like a confused dog. They don't have the money to do the tests to see if stuff is safe, save that kind of worrying for 10 years from now when everyone who eats something off the street gets cancer.
5 / 5 (2) Mar 30, 2011
Does this help make our environment better, or is another incentive for polluters to continue poisoning our environment so they can make another buck off of us? Hmmmmm. Let's make more fly ash!
not rated yet Mar 30, 2011
whatever they do i hope they find a way to take the razor edges off the stuff.in the St Croix Valley area of Minnesota they tried spreading it on the roads in the winter rather than sand and it cut the car tires up so fast the program was stopped after one winter.there is a power plant near Stillwater Mn with a huge pile of fly ash.this was back in the late 70's and after a winter of daily commutes i needed new rubber all the way around and when i asked at the local shop that was the story i got.
not rated yet Mar 30, 2011
Hardly a new use for coal waste, in UK we have breeze / brieze blocks from "late 16th century: from French braise, (earlier) brese 'live coals'" Over there you have cinder / clinker blocks. I don't see a Big Coal conspiracy. In Mayhew's London Labour and London Poor he talks about people sorting this out to sell for brick manufacture.
not rated yet Mar 30, 2011
In this country, in my state, nobody is interested in prolonging the longevity of roads and bridges. The planned lifecycle of these public works is job security for the criminals and cheats who control the Department of Transportation. I would wager it is like this in most states. Graft abounds in many construction industries.
not rated yet Mar 30, 2011
Fly Ash has been used as a partial substitute for cement in ready mix blends for years. Cement uses a huge amount of energy to produce most all of it comes from Asia nowadays. The article just keep referring to the "coating" so I'm not quite sure if its an after treatment to restore older concrete or a new concrete blend.
not rated yet Mar 30, 2011
The pirates that run the show are not interested in long lasting infrastructure.

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