There is some debate over the greenness of coal fly ash. Fly ash is a by-product of coal burning, and it contains heavy metals like lead and mercury. But when added to concrete mixes, it has several advantages, including that it increases recycled content and reduces the amount of Portland cement needed in the mix.
Some environmentalists are eager to encapsulate the fly ash inside concrete; theoretically leaching rates would be much lower than through traditional disposal means. Proponents of fly ash recycling also point out that it reduces the amount of Portland cement needed in concrete. Portland cement is a very energy- and carbon-intensive product to produce, so some argue that fly ash therefore reduces the carbon footprint of the entire concrete mix.
In addition, because fly ash is a hazardous material, some wonder whether it renders the concrete hazardous too, during both use and disposal. The main concern is whether the fly ash leaches heavy metals after the concrete cures, introducing these toxic substances into homes. Finally, some environmentalists argue that green builders are buying into the coal industry’s efforts to rebrand hazardous waste as recycled material.
Even when a product is described as “0 g/L VOC” (“g/L” stands for “grams per liter”) it may still contain VOCs. The EPA’s reporting requirements for VOCs are limited to solvents that have a high potential to form ground-level ozone and smog. Organic solvents that have low smog and ozone-forming potential are classified as exempt in calculating the VOC content of a product, although they are still volatile and organic.
What’s LEED All About, Anyway?
“Always be on the lookout for hidden environmental costs,” says Dwayne Fuhlhage, sustainability and environment director at Prosoco, a manufacturer of specialty cleaners and protective treatments for masonry and concrete. “Some common concrete dust-proofer and hardener products are alkaline and require postapplication rinsing, with associated burdens to municipal treatment systems or offsite disposal,” he says. “Topcoats and waxes that require frequent stripping and reapplication are not a sustainable choice.”
Finished concrete floors can last as long as the building they’re housed in with proper maintenance. They contribute to good indoor air quality by minimizing dust and moisture sinks that can collect allergens and irritants.
More: 5 Benefits to Concrete Floors for Everyday Living