http://www.fhwa.dot.gov/
This will be a somewhat repetitive dispatch; but, with some additional information.
We submit it primarily to provide some original-source documentation and to begin further addressing one question that was raised to us by one of our informal consultants, which we have treated somewhat briefly in earlier reports.
There will be a lot of future ground to cover, but:
The document we enclose, via the initial link above, is one about which we have previously reported.
Last December, in an earlier dispatch, now accessible on the West Virginia Coal Association's web site via:
we made report of a continuing education course for road construction, or any, really, civil, engineers, that had been put together by a private contractor for the US Federal Highways Administration, represented as:
"Fly Ash Facts for Highway Engineers; Course No: T06-003; Continuing Education and Development, Inc.; Stony Point, NY 10980; (Reference): Report No. FHWA-IF-03-019; Title: Fly Ash Facts for Highway Engineers; 2003; American Coal Ash Association; Contract No. DTHF61-02-X-00044; Sponsoring Agency: Federal Highway Administration. Coal fly ash is a coal combustion product that has numerous applications in highway construction."
As noted, that continuing education course was based on the original Federal Highways Administration "Report No. FHWA-IF-03-019; Title: Fly Ash Facts for Highway Engineers", and, herein, we wanted to provide you with linkage to that original, unabridged, source documentation.
The FHWA contract specifics are as stated in our previous report, and we won't recap them here.
However, a few excerpts from the Abstract and Summary seem in order, as follows:
"Fly Ash Facts for Highway Engineers; Report Number: FHWA-IF-03-019; Contract: DTFH61-02-X-00044
Date: June 13, 2003
Coal fly ash is a coal combustion product that has numerous applications in highway construction.
Since the first edition of 'Fly Ash Facts for Highway Engineers' in 1986, the use of fly ash in highway construction has increased and new applications have been developed. This document provides basic technical information about the various uses of fly ash in highway construction that advances its use in ways that are technically sound, commercially competitive, and environmentally safe."
Fly ash has been used in roadways and interstate highways since the early 1950s.
In 1974, the FHWA encouraged the use of fly ash in concrete pavement with Notice N 5080.4, which urged states to allow partial substitution of fly ash for cement whenever feasible.
In addition, in January 1983, the Environmental Protection Agency published federal comprehensive procurement guidelines for cement and concrete containing fly ash to encourage the utilization of fly ash and establish compliance deadlines.
(A question: Is a copy of those EPA "procurement guidelines" lying open and well-used on the desk of every single design and contract engineer in the West Virginia Department of Transportation's Division of Highways and the Pennsylvania Department of Transportation's Bureau of Construction and Materials? Those are, we believe, the appropriate design and specification offices.)
This document is sponsored by the U.S. Department of Transportation, through the Federal Highway Administration, in cooperation with the American Coal Ash Association and the United States Environmental Protection Agency.
The United States Environmental Protection Agency supports the beneficial use of coal combustion products as an important priority and endorses efforts by the Federal Highway Administration as described in this document.
FLY ASH IN PORTLAND CEMENT CONCRETE: Fly ash is used in concrete admixtures to enhance the
performance of concrete. Portland cement contains about 65 percent lime. Some of this lime becomes free and available during the hydration process. When fly ash is present with free lime, it reacts chemically to form additional cementitious materials, improving many of the properties of the concrete.
Benefits. The many benefits of incorporating fly ash into a Portland Cement Concrete (PCC) have been demonstrated through extensive research and countless highway and bridge construction projects. Benefits to concrete vary depending on the type of fly ash, proportion used, other mix ingredients, mixing procedure, field conditions and placement.
Some of the benefits of fly ash in concrete (include): Higher ultimate strength; Improved workability; Reduced bleeding; Reduced heat of hydration; Reduced permeability; Increased resistance to sulfate attack; Increased resistance to alkali-silica reactivity (ASR); Lowered costs; Reduced shrinkage; Increased durability.
FLY ASH IN STABILIZED BASE COURSE: Fly ash and lime can be combined with aggregate to produce a quality stabilized base course. These road bases are referred to as pozzolanic-stabilized mixtures (PSMs). Typical fly ash contents may vary from 12 to 14 percent with corresponding lime contents of three to five percent. Portland cement may also be used in lieu of lime to increase early age strengths. The resulting material is produced, placed, and looks like cement stabilized aggregate base.
FLY ASH IN FLOWABLE FILL: Flowable fill is a mixture of coal fly ash, water, and portland cement that flows like a liquid, sets up like a solid, is self leveling, and requires no compaction or vibration to achieve
maximum density. In addition to these benefits, a properly designed flowable fill may be excavated later. For some mixes, an optional filler material such as sand, bottom ash, or quarry fines, is added. Flowable fill is also referred to as controlled low-strength material, flowable mortar, or controlled density fill. It is designed
to function in the place of conventional backfill materials such as soil, sand, or gravel and to alleviate problems and restrictions generally associated with the placement of these materials.
The benefits ... include: placement in any weather, even under freezing conditions; 100 percent density with no compactive effort; Fills around/under structures inaccessible to conventional fill placement techniques; Increases soil-bearing capacities; Prevents post-fill settlement problems; Increases the speed and ease of backfilling operations; Decreases the variability in the density of the backfilled materials; Improves safety at the job site and reduces labor costs; Decreases excavation costs; Allows easy excavation later when properly designed.
FLY ASH IN STRUCTURAL FILLS/EMBANKMENTS: Fly ash can be used as a borrow material to construct fills and embankments. When fly ash is compacted in lifts, a structural fill is constructed that is capable of supporting highway buildings or other structures. Fly ash has been used in the construction of structural fills/embankments that range from small fills for road shoulders to large fills for interstate highway embankments.
When used in structural fills and embankments, fly ash offers several advantages over soil and rock (i.e.,): Cost-effective where available in bulk quantities; Eliminates the need to purchase, permit, and operate a borrow pit; Can be placed over low bearing strength soils; Ease of handling and compaction reduce construction time and equipment costs.
FLY ASH IN SOIL IMPROVEMENT: Fly ash is an effective agent for chemical and/or mechanical stabilization of soils. Typical applications include: soil stabilization, soil drying, and control of shrink-swell.
Fly ash provides the following benefits when used to improve soil conditions: Eliminates need for expensive borrow materials; Expedites construction by improving excessively wet or unstable subgrade; By improving subgrade conditions, promotes cost savings through reduction in the required pavement thickness; Can reduce or eliminate the need for more expensive natural aggregates in the pavement cross-section.
FLY ASH IN ASPHALT PAVEMENTS: Fly ash can be used as mineral filler in HMA paving applications. Mineral fillers increase the stiffness of the asphalt mortar matrix, improving the rutting resistance of pavements, and the durability of the mix. Fly ash will typically meet mineral filler specifications for gradation, organic impurities, and plasticity. The benefits of fly ash include: Reduced potential for asphalt stripping due to hydrophobic properties of fly ash; Lime in some fly ashes may also reduce stripping; May afford a lower cost than other mineral fillers.
FLY ASH IN GROUTS FOR PAVEMENT SUBSEALING: Grouts are proportioned mixtures of fly ash, water, and other materials used to fill voids under a pavement system without raising the slabs (subsealing), or to raise and support concrete pavements at specified grade tolerances by drilling and injecting the grout under specified areas of the pavement. Fly ash grouts can: Be used to correct undermining without removing overlying pavement; be accomplished quickly with minimum disturbance to traffic; Develop high ultimate strength."
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Should you have enough interest in such potentials for the constructive and profitable use of our solid Coal Utilization Byproducts to want more information, we do suggest you examine the full, official United States Government document as accessible via the initial link; and, as also accessible in somewhat abridged form in our earlier report concerning "Fly Ash Facts for Highway Engineers; Course No: T06-003; Continuing Education and Development, Inc.", as cited above.
One issue we did want to address somewhat further herein, however, is the use of Coal Ash, as above, in such things as "Stabilized Base Course; Flowable Fill; Structural Fills/Embankments; and, Soil Improvement".
When Fly Ash is utilized, as the FHWA suggests, as a raw material in the making of Portland Cement, and, as an additional aggregate, in Portland Cement Concrete, as we've documented now in numerous reports, such as:
West Virginia Coal Association | Canada Coal Ash Cement | Research & Development; concerning: "United States Patent 5,837,052 - Process for Producing Cement Clinker Containing Coal Ash; 1998; Assignee: Lafarge Canada, Inc.; Abstract: Contaminated coal ash, for example flyash contaminated with carbon is introduced to hot clinker in a cooler downstream of a cement kiln; the carbon is combusted in the cooler to provide a cement clinker having an effective content of flyash free of carbon; this permits use of flyash contaminated with carbon without the need for separate special steps for carbon removal; volatile contaminants or contaminants having a volatile component, for example adsorbed ammonia are similarly removed in the cooler by volatilization"; and:
West Virginia Coal Association | California "Builds It Green" with Coal Ash Concrete | Research & Development; concerning: "Coal Fly Ash: The Most Powerful Tool for Sustainability of the Concrete Industry; P.K. Mehta; University of California, Berkeley, CA; It has recently been proved that use of high volumes of coal fly ash can produce low cost, durable, sustainable cement and concrete mixtures that would reduce the carbon footprint of both the cement and the power generation industries. The nature of fly ash, tiny spherically shaped particles that act as ball bearings, make it able to fill small voids and produce denser concrete that requires less water for installation, resulting in water savings. Its density makes it less permeable to water in finished form, protecting reinforcing steel and increasing the concrete’s durability";
any objectionable elements and molecules which might, or might not, be contained in the Coal Ash, and which some of our tremulous brethren fear might sneak into our environment and poison our progeny, would, if not destroyed in the cement-making process, be chemically and mechanically locked up in the cement and concrete tighter than a bull's butt at fly time well unto the end of the world as we know it, over vast geologic epochs.
However, in the other uses for Coal Ash, such as "Stabilized Base Course; Flowable Fill", etc., there is much less chemical bonding or transformation taking place; and, concerns have been raised that objectionable elements, especially metals of various sorts, and their compounds, might somehow "leach" out of the Coal Ash emplacements and contaminate the environment.
As we've documented in a number of previous reports, such as:
West Virginia Coal Association | USDOE Says Coal Ash Could End Aluminum Ore Imports | Research & Development; concerning the: "Economic Metal Recovery from Fly Ash; 1981; Research Organization: Oak Ridge National Laboratory, USDOE; Abstract: Although most coal combustion ash produced in the United States is discarded as a waste, results are presented to show that fly ash can be an economical source of Al2O3, Fe2/O3, and possibly several other metals, many of which are presently being imported. Although several metal recovery processes were studied, only the two of greatest economic potential and widest applicability were given detailed economic evaluation; the direct acid leach of ash with HCl (a minimum treatment process) and a pressure digestion-acid leach (a maximum recovery process). Results show that both methods can remove from fly ash all metals that would otherwise be available for release to the environment after disposal and that a major portion of the leached metals can be separated in saleable form. Economic analyses indicate that the direct acid leach process is most attractive. A capital investment of $38.2 million (to process a specified amount) of ash per year (will generate) a net yearly cash flow of $15.2 million. Additional economic benefits will result from the recovery of these metals through elimination of the higher ash disposal costs that may be required for fly ash containing trace metals. National benefits will also result from reduced importation of metals and ores";
the two major metal constituents, Iron and Aluminum, of Coal Ash can, in fact, be profitably extracted from Coal Ash, using processes that would also, if implemented, enable the further extraction of "several other metals" from that Coal Ash; and, the subsequent use of the extracted Ash residue, without any significant amounts of metal left in that residue to be leached out.
In point of fact, the work on the development of technologies for metals extraction from Coal Ash has been so extensive, that, based on the profitable extraction technologies for Iron and Aluminum, virtually all metals of any significance in Coal Ash can be extracted, leaving behind a residue, which, as will be seen in future reports, is, by all sensible parameters, totally innocuous and would be perfectly suitable for use in any of the applications suggested above by the Federal Highways Administration.
Further, a large number of studies, including one of some significance performed by WVU, which we might or might not treat in future reports, strongly supports the conclusion that, whether or not most or all of the metals are first removed from Coal Ash, as via the above-cited USDOE report "Economic Metal Recovery from Fly Ash", Coal Ash, utilized without chemical transformation or mechanical encapsulation, i.e., as in its uses as a raw material for cement and as an aggregate in concrete, but, instead, relatively unconsolidated, as in the FHWA's "Flowable Fill" and "Soil Improvement" applications, still represents a largely innocuous material that can be utilized in environmental applications without presenting contamination hazards that exceed established guidelines.
The reports of studies demonstrating such facts are so carefully, courtesy inhibits our use of a less delicate adjective, worded, however, with no one, apparently, having the intestinal fortitude to openly confront the, we contend deliberately, cultivated image of Coal Ash as some sort of hazardous waste, that parsing out their true results and presenting them in clear fashion is proving something of a challenge.
We'll keep trying to apply both industry and civility to that task; but, in the meantime, following, from Minnesota, where maybe they're a little more plain-spoken, is one evaluation of the use of Coal Ash in its raw, unconsolidated and un-extracted, form as, as in the FHWA's "FLY ASH IN SOIL IMPROVEMENT: Fly ash is an effective agent for chemical and/or mechanical stabilization of soils", applied to, and blended into, soils for the purposes of ground stabilization.
As seen in excerpts from the following link:
Energy Citations Database (ECD) - - Document #824927
"Environmental Evaluation for Utilization of Ash in Soil Stabilization
August, 2001
USDOE Contract: FC26-98FT40321; OSTI ID: 824927
Authors: D. J. Hassett and L. V. Heebink
Research Organization: University of North Dakota
Abstract: The Minnesota Pollution Control Agency (MPCA) approved the use of coal ash in soil stabilization, indicating that environmental data needed to be generated. The overall project goal is to evaluate the potential for release of constituents into the environment from ash used in soil stabilization projects. Supporting objectives are: (1) To ensure sample integrity through implementation of a sample collection, preservation, and storage protocol to avoid analyte concentration or loss. (2) To evaluate the potential of each component (ash, soil, water) of the stabilized soil to contribute to environmental release of analytes of interest. (3) To use laboratory leaching methods to evaluate the potential for release of constituents to the environment. (4) To facilitate collection of and to evaluate samples from a field runoff demonstration effort. The results of this study indicated limited mobility of the coal combustion fly ash constituents in laboratory tests and the field runoff samples. The results presented support previous work showing little to negligible impact on water quality. This and past work indicates that soil stabilization is an environmentally beneficial CCB (i.e., "Coal Combustion Byproduct") utilization application as encouraged by the U.S. Environmental Protection Agency. This project addressed the regulatory-driven environmental aspect of fly ash use for soil stabilization, but the demonstrated engineering performance and economic advantages also indicate that the use of CCBs in soil stabilization can and should become an accepted engineering option."
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Clearly stated, in sum:
Coal "ash used in soil stabilization" has "negligible impact on water quality" and "is an environmentally beneficial CCB (i.e., "Coal Combustion Byproduct") utilization application" with "demonstrated engineering performance and economic advantages" that "should become an accepted engineering option".