02/07/2014: EPA Evaluation Finds Use of Coal Ash in Concrete and Wallboard Appropriate
This is an EPA news release from just a few months ago, sort of reaffirming their prior approval and promotion of the use of Coal ash in "encapsulated" applications, specifically as an aggregate in, or additive to, cement and concrete.
Their reaffirmation also includes the use of desulfurization synthetic gypsum in wallboard.
Hadn't seen it elsewhere publicized - - never saw it posted on an FOC site, for instance, although it might well have appeared and we missed it - - but we wanted to make certain you were aware of it - we might or might not find a way to work it into a CoalTL post we're composing for dispatch tomorrow concerning the fact, that, interestingly, the White House is now making available on their own web site info about the constructive use of Coal Ash about which we reported some time ago via CoalTL.
The White House is making available a complete, down-loadable document we'll send along a file of..
We note that the EPA's statement: "use in concrete as a substitute for portland cement", as below, though in some cases, but not all, true, is a bit narrow.
Keep in mind that the chemical differences between Class F and Class C Ash affect the way they perform, the different ways they react, in cement mixes.
Class C can sometimes substitute directly for some of the "portland cement", Class F generally speaking can't.
But, Ash can also be used as a substitute for at least some of the fine and, with some processing, the coarse aggregate; and, in some of those applications it's, especially Class F's, pozzolanic properties enhance the ultimate performance of the cement, and, thus, of the overall composite.
A "Q&A" exposition of those issues, if they remain unfamiliar, can be had via:
http://www.boralna.com/flyash/faq.asp
But, as might be apparent, the chemistries are damnably complicated, so maybe generalizations are okay.
Keep in mind that Ash can, as well, in addition, be used a raw material for making the cement itself.
As a, perhaps interesting, aside, we reported some time ago that India was exporting Coal Ash to Saudi Arabia. Since then, a Saudi-owned company has been set up to facilitate Ash importation into, and Ash distribution within, the Kingdom. Their web site is still mostly in Arabic, though, with limited English translation so far. We'll wait to see if they flesh it out a bit before reporting on it.
Excerpts from the EPA news release follow. Hopefully of interest. Melissa and Joe
"EPA Evaluation Finds Use of Coal Ash in Concrete and Wallboard Appropriate
Release Date: 02/07/2014
Contact Information: Enesta Jones, Jones.enesta@epa.gov, 202-564-7873, 202-564-4355
WASHINGTON – Using a newly developed methodology, the U.S. Environmental Protection Agency (EPA) today released its evaluation of the two largest beneficial uses of encapsulated coal combustion residuals (CCR or coal ash): use in concrete as a substitute for portland cement, and the use of flue gas desulfurization gypsum as a substitute for mined gypsum in wallboard. EPA’s evaluation concluded that the beneficial use of encapsulated CCRs in concrete and wallboard is appropriate because they are comparable to virgin materials or below the agency’s health and environmental benchmarks.
These two uses account for nearly half of the total amount of coal ash that is beneficially used.
“The protective reuse of coal ash advances sustainability by saving valuable resources, reducing costs, and lessening environmental impacts, including reducing greenhouse gas emissions,” said Mathy Stanislaus, assistant administrator for EPA’s Office of Solid Waste and Emergency Response.
In evaluating these two beneficial uses, EPA used its newly developed, Methodology for Evaluating Encapsulated Beneficial Uses of Coal Combustion Residuals. The methodology is intended to assist states and other interested parties with evaluating and making informed determinations about encapsulated beneficial uses of CCRs.
Coal ash is formed when coal is burned in boilers that generate steam for power generation and industrial applications. Slightly more than half of coal ash is disposed of in dry landfills and surface impoundments. The remainder of coal ash is used beneficially, as well as in mining applications."