United States Patent: 4256504


Herein, from the United States Department of the Interior, we have further confirmation of the fact that Coal power plant Fly Ash can be utilized as a raw material in the making of Portland-type Cement, and, thus, concrete; a use which, when combined with the potential for using additional Fly Ash in various forms as an aggregate for the concrete, offers an outlet of extraordinary size and volume for the solid by-products arising from our invaluable and essential use of Coal in the generation of electrical power.


We remind you that the Department of the Interior, through their Bureau of Reclamation, has a long history of productively utilizing Coal ash.

As we've separately documented in other reports, and as can be learned from the Federal Highways Administration via the link:


Fly Ash; wherein we're told: "The major breakthrough in using fly ash in concrete was the construction of Hungry Horse Dam in 1948, utilizing 120,000 metric tons of fly ash. This decision by the U.S. Bureau of Reclamation paved the way for using fly ash in concrete constructions";


it has long been known that Coal Ash can be utilized as a fine aggregate in high-performance structural concrete applications.


Further, as seen in our report of:


Consol Converts Coal Ash to Concrete Aggregate | Research & Development; concerning: "United States Patent 5,364,572 - Process for Making High-Strength Synthetic Aggregates; 1994; Consolidation Coal Company; Abstract: A process for making high-strength aggregates ... containing coal combustion ash";


we can produce coarse aggregates for use in concrete, as well, out of Coal Ash.


And, a close read of Consol's "United States Patent 5,364,572", as we point out in our report, reveals that Flue Gas Desulfurization, "FGD", wastes, consisting mostly of Calcium Sulfate, can be combined with the Fly Ash in the making of the cementitious compound from which the aggregates are formed.


That fact is actually key to yet another technology developed by the United States Department of the Interior's Bureau of Reclamation, in addition to the use of Fly Ash as an aggregate, as in the Hungry Horse Dam application noted above.


In confirmation of other documents attesting to the potentials we have brought to your attention, we see herein that a Bureau of Reclamation scientist developed proprietary technology, similar chemically to the above-cited Consol process of US Patent 5,364,572, wherein both Coal Fly Ash and the Calcium Sulfate product of FGD scrubbers can be combined in the making of a substitute Portland Cement.


Comment, and additional links, follow and are inserted within our excerpts from the initial link to:


"United States Patent 4,256,504 - Fly Ash-based Cement


Date: 1981


Inventor: Edwin Dunstan, Jr., CO


Assignee: The United States of America (as represented by the Secretary of the Interior)


(Note, the United States Patent and Trademark Office web-accessible version of this document is somewhat truncated, and the actual "Assignee", is somewhat unclear. However, a full facsimile of the original document itself, as maintained on an independent web site, and as accessible via the following link:


Fly ash-based cement;


confirms that our above reproduction is accurate. Further, via the link:


NRMCA Presents Awards at Annual Convention - Associations, Awards - Concrete Construction;


we can learn that:


"The National Ready Mixed Concrete Association has presented the following awards during its annual convention which was just completed in Las Vegas prior to the opening of this week’s ConExpo-Con/Agg 2011 Show:

2011 Richard D. Gaynor Award – Edwin R. Dunstan, Jr. ... Dunstan has worked as a concrete materials engineer for 38 years. From 1972-1980 he was a quality control and research engineer for the U.S. Bureau of Reclamation in Denver. From 1980-1988, he worked as an independent concrete materials consultant and educator in Colorado. He joined Florida Mining and Materials in 1988 as a concrete materials-quality control engineer and remained with the company through acquisitions by Southdown and Cemex. He retired from Cemex in August 2008 as director of technical services, ready mix. Now semi-retired, he remains active in the concrete industry as a concrete materials consultant and examiner for the Construction Materials Engineering Council in Orlando, FL. Dunstan holds Bachelor’s and Master’s degrees from Kansas State University in Manhattan";

and, thus, conclude that the inventor of our subject herein, Edwin Dunstan, was, indeed, employed by the United States Department of Interior's Bureau of Reclamation at the time the technology disclosed by our subject, "United States Patent 4,256,504 - Fly Ash-based Cement", was being developed.)

Abstract: A cement composition comprising a high calcium-content fly ash and calcium sulfate, and mortar and concrete compositions containing the cement.

Claims: A cement composition consisting essentially of (1) a major proportion of a fly ash ... and (2) about 5 to 15 percent by weight of calcium sulfate. 

The composition ... in which the calcium sulfate is anhydrous. 

The composition ... in which the calcium sulfate is anhydrite.

(Note, that, as can be learned, again from the Federal Highways Administration, via the link:

FGD Scrubber Material - Material Description - User Guidelines for Waste and Byproduct Materials in Pavement Construction - FH; concerning:


"User Guidelines for Waste and Byproduct Materials in Pavement Construction; FGD Scubber Material;

The burning of pulverized coal in electric power plants produces sulfur dioxide (SO2) gas emissions. The 1990 Clean Air Act and its subsequent amendments mandated the reduction of power plant SO2 emissions. The Best Demonstrated Available Technology (BDAT) for reducing SO2 emissions is wet scrubber flue gas desulfurization (FGD) systems. These systems are designed to introduce an alkaline sorbent consisting of lime or limestone (primarily limestone) in a spray form into the exhaust gas system of a coal-fired boiler. The alkali reacts with the SO2 gas and is collected in a liquid form as calcium sulfite or calcium sulfate slurry. The calcium sulfite or sulfate is allowed to settle out as most of the water is recycled";

a portion of FGD scrubber sludge comprises "calcium sulfite"; and, if that is unwanted, other web-based references attest that such "calcium sulfite" is readily converted into more of the specified "calcium sulfate" by the simple expedient of blowing air through water solutions or suspensions of the Calcium Sulfite.

Waste power plant heat, we suggest, could be utilized to render the "calcium sulfate ...anhydrous", or, more simply, "dry"; and, to convert it into the "anhydrite" form of the mineral.).

A mortar composition comprising a major proportion of sand and a minor proportion of the (claimed Fly Ash) cement composition.

(Note that fine Coal Fly Ash, as in the Hungry Horse Dam project, as cited above, could substitute for at least some of the "sand".)

The concrete composition comprising a major proportion of sand and an aggregate and a minor proportion of the (claimed Fly Ash) cement composition.

(Note that the Fly Ash-based product of Consol's "US Patent 5,364,572 - Process for Making High-Strength Synthetic Aggregates", as cited above, could substitute for at least some of the "aggregate".)

Description: Fly ash, the residue collected in the flues of coal-burning power plants, has been used as a component of concrete admixtures to replace a portion e.g., about 10 to 25 percent, of the conventionally-employed Portland cement. This combination of fly ash and Portland cement affords a substantial reduction in cost since the fly ash costs much less than Portland cement. Furthermore, Portland cement production requires large amounts of energy and, consequently, use of fly ash reduces energy demand.

(As we've previously documented, and as we will again address in reports to follow, the making of traditional Portland Cement, in addition to consuming "large amounts of energy", also generates large amounts of CO2; and, that, too, would be reduced through the substitution of Fly Ash for some of the Portland Cement.) 

It has now been found, according to the present invention, that a cement comprising a high calcium-content fly ash and calcium sulfate has similar advantages, but to a much greater degree since all of the Portland cement is replaced with much less expensive materials, and the energy required to produce the compositions of the invention is minimal.

Fly ash is the residue of powdered coal burned in power plants at temperatures generally in excess of 2500F. The chemical makeup of this residue is a function of the coal burned by the power plant. In particular, the amount of calcium bound in glass particles in the fly ash varies over a wide range. It has been found, as one aspect of the present invention, that a calcium content in excess of about 20 percent, and preferably in excess of 26 percent, by weight of the fly ash is essential to achievement of the necessary compressive strength to permit total replacement of Portland cement. Calcium content of the fly ash is readily determined by conventional means such as that outlined in ASTM designation C114, "Chemical Analysis of Hydraulic Cement", with the results usually being reported as percent CaO.

The calcium sulfate, which constitutes the other essential ingredient of the cement composition of the invention, may be of many forms, but is preferably anhydrous or in the form of the hemihydrate, i.e., CaSO4.1/2H.sub.2O (plaster of paris). It may consist of anhydrite, a naturally occurring CaSO4, or it may be prepared by dehydration of hydrated calcium sulfate such as gypsum.

(See, for instance, our report of:

Synthetic Gypsum from Coal Power Plant Flue Gas | Research & Development; concerning, in part: "United States Patent 7,776,150 - Process and Apparatus for Handling Synthetic Gypsum; 2010; Assignees: Koppern Equipment Company, NC, and Giant Cement Company, SC; Abstract: Method and apparatus for converting wet synthetic gypsum from a flue desulphurization process (FGD)".)

Optimum amounts of the calcium sulfate will depend on the specific fly ash and calcium sulfate employed. Suitable amounts, however, will generally range from about 5 to 15 percent by weight.

The cement composition of the invention is prepared by thorough admixing of the fly ash and calcium sulfate, in finely divided form, by conventional means. Since the fly ash normally occurs in finely divided form, most often collected electrostatically as a dust, further reduction is usually not necessary. The calcium sulfate is generally available in powder form suitable for admixture with the fly ash. Particle size of the calcium sulfate should be similar to that of Portland cement. Mortar or concrete compositions may be prepared from the cement of the invention by addition of conventional materials, i.e., sand or a combination of sand and an aggregate such as gravel, broken stones, pebbles, cinders, etc. These materials, and their amounts, are essentially the same as those employed with other cements, such as Portland cements, and are well known to those versed in the art.

Use of the cement and corresponding mortar and concrete compositions of the invention are also conventional and consist simply of addition and admixture of water in an amount sufficient to form a paste. The amount of water required is, however, generally considerably less than that required for Portland cement concretes.

Example:A mortar was prepared by admixing 675 grams of a fly ash from Commanche Power Plant, Pueblo, Colorado, containing 32 percent calcium, with 75 grams of finely divided anhydrous calcium sulfate. The latter was prepared by dehydration of technical grade CaSO4-2H2O at 200C.

302 grams of water ... and 2062 grams of silica sand graded according to ASTM designation C109 were added and thoroughly mixed with the cement to form a mortar which was then formed into 2- by 2-inch cubes according to the ASTM procedure. Compressive strengths of the cubes were then measured according to the procedure of the ASTM procedure.

Compressive strength at 28 days, the most common referenced strength, was 5770 pounds per square inch.

By comparison, cubes of Type II Portland cement mortar prepared and tested in the same manner showed a compressive strength of 5540 pounds per square inch."


Thus: The United States Department of the Interior owns the rights to a process that would enable the making of Cement that is at least as strong as, and perhaps a little stronger than, conventional Portland Cement, and which would require less energy and less water to make than conventional Portland Cement, out of our unwanted Coal-fired power plant Fly Ash, along with some material scrounged from our equally unwanted Flue Gas Desulfurization scrubber sludge.

And, such applications for Coal Ash, as we will, again, further document in coming reports, would reduce the total emissions of Carbon Dioxide, relative to the total combined amount of CO2 emitted by Coal-fired power generation and conventional Cement making as they are now separately practiced.

Finally, just as with the technologies we've previously documented via, for only two examples:

USDOE 1976 Atmospheric CO2 to Methanol | Research & Development; concerning: "United States Patent 3,959,094 - Electrolytic Synthesis of Methanol from CO2; 1976; Assignee: The USA as represented by the USDOE; A method and system for synthesizing methanol from the CO2 in air using electric power"; and:


USDOE 1986 Ethylene from Coal | Research & Development; concerning: "United States Patent 4,563,197 - Production of Ethylene and Other Hydrocarbons from Coal; 1986; Assignee: The USA, as represented by the USDOE; A process for the production of economically significant amounts of ethyl and other hydrocarbon compounds, such as benzene, from coal";


the process for utilizing Coal power plant Fly Ash and Coal power plant Flue Gas Desulfurization Sludge in the making of a higher-performance, more-economical Portland-type cement, as disclosed by our subject,

"United States Patent 4,256,504 - Fly Ash-based Cement", is a technology that was developed in United States Government labs owned by all United States citizens, a technology that was developed by United States Government scientists employed, and paid, through their taxes, by all United States citizens.


Why, as with the Government-owned "US Patent 3,959,094" and "US Patent 4,563,197", have the people who own this Fly Ash utilization technology, i.e., us, all of us, and especially those of us resident in West Virginia, Pennsylvania and the rest of United States Coal Country, not even been told that such a technology exists and that we own such a technology - much less been afforded the opportunity to put the technology into practice; and, to, thereby, improve both our environment and our economy in the course of bringing more jobs, more profit and a better future to United States Coal Country, all as a consequence of making such a higher-quality, higher-performance, but lower-cost, Cement out of our Coal-fired power plant Fly Ash?

West Virginia Coal Association - PO Box 3923 - Charleston, WV 25339 | 304-342-4153 | website developed by brickswithoutstraw