We've documented for you in a number of reports that Coal Ash added to Portland-type Cement can, as seen, for example, in:
West Virginia Coal Association | Coal Ash Concrete More Durable, Resists Chemical Attack | Research & Development; concerning: "United States Patent 5,772,752 - Sulfate and Acid Resistant Concrete and Mortar; 1998; Assignee: New Jersey Institute of Technology; Abstract: The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction and other applications, which hardenable mixtures demonstrate significant levels of acid and sulfate resistance while maintaining acceptable compressive strength properties"; and:
West Virginia Coal Association | US Government Coal Ash Cement Stronger than Portland Cement | Research & Development; concerning: "United States Patent 4,256,504 - Fly Ash-based Cement; 1981; Assignee: The United States of America (as represented by the Secretary of the Interior); Abstract: A cement composition comprising a high calcium-content fly ash and calcium sulfate, and mortar and concrete compositions containing the cement. 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. 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. 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";
result in the production of a Portland-type Cement, and subsequently Concrete, that is stronger; more resistant to chemical attack and corrosion, specifically sulfate attack, and, costs less than standard Portland Cement Concrete.
Some of those facts are confirmed again herein by both our United States Government technical experts in the US Patent and Trademark Office, and by the largest manufacturer of Cement in Japan, who maintain manufacturing facilities throughout the Asian Pacific region.
Comment follows excerpts from the initial link in this dispatch to the recent:
"United States Patent 8,133,317 - Cement Additive and Cement Composition
Patent US8133317 - Cement additive and cement composition - Google Patents
Cement additive and cement composition - Taiheiyo Cement Corporation
Date: March 13, 2012
Inventors: Hiroshi Hirao, et. al., Japan
Assignee: Taiheiyo Cement Corporation, Tokyo, and DC Co. Ltd., Kawasaki-shi
(TAIHEIYO CEMENT; Taiheiyo Cement - Wikipedia, the free encyclopedia)
Abstract: A cement additive contains industrial waste and has the effect of inhibiting formation of monosulfate in a hardened cementitious material. The cement additive contains specifically calcium carbonate, gypsum and coal ash and/or blast-furnace slag powder. This enables efficient use of industrial waste, allows inhibiting monosulfate formation in the hardened cementitious material, and allows producing a hardened cementitious material having good durability (sulfate resistance).
Claims: A cement additive containing industrial waste and having an effect of inhibiting monosulfate formation in a hardened cementitious material, said cement additive comprising calcium carbonate, gypsum, blast-furnace slag powder and coal ash, wherein said calcium carbonate is blended in an amount of 0.5 to 160 parts by weight and said gypsum (anhydrous basis) is blended in an amount of 5 to 150 parts by weight relative to 100 parts by weight of said coal ash and said blast-furnace slag powder, and a blending ratio (weight basis) of said gypsum and said calcium carbonate is 1:0.1 to 15.
(The needed "gypsum", we remind you, can, as seen for only one example in:
West Virginia Coal Association | Pittsburgh Makes Coal Flue Gas Gypsum for Fly Ash Cement | Research & Development; concerning: "United States Patent 5,312,609 - Sulfur Dioxide Removal from Gaseous Streams with Gypsum Product Formation; 1994; Assignee: Dravo Lime Company, Pittsburgh; Abstract: A method is provided for removing sulfur dioxide from a hot gaseous stream while directly producing .alpha.-hemihydrate gypsum from a scrubber effluent";
itself be made from the effluent of a Coal flue gas desulfurization scrubber. The needed additive "calcium carbonate" is just plain old Limestone, as Taiheiyo Cement does get around to specifying, and which is pretty much standard raw material feed for a Cement kiln, in any case.
Note, too, that "blast furnace slag", another Coal-related industrial by-product, isn't really needed. There are a great many published technologies concerning the manufacture of "blast furnace slag" Cement, similar to those concerning the use of Fly Ash as a Cement-making raw material. We haven't dealt with those over the course of our reportage since there just aren't any Coal-fired, steel-making "blast furnaces" operating in the United States right now, at least on a scale that would make exposition of and reportage on such slag-use technologies pertinent and useful.)
The cement additive ... containing coal ash and/or blast-furnace slag powder as said industrial waste; calcium carbonate as said industrial waste and/or calcium carbonate not as said industrial waste; and gypsum as said industrial waste and/or gypsum not as said industrial waste.
(Again, as in "and/or", the "blast-furnace slag" isn't required. And, as in our above citation of our report concerning "United States Patent 5,312,609 - Sulfur Dioxide Removal from Gaseous Streams with Gypsum Product Formation", we should much prefer that "gypsum as ... industrial waste" be used herein in conjunction with the "coal ash”.)
The cement additive ... containing limestone powder as said calcium carbonate.
Background and Field: The present invention relates to a cement additive using industrial waste as main raw material, and to a cement composition comprising such a cement additive.
The durability of ... hardened cementitious material decreases markedly when the hardened cementitious material gives rise to sulfate expansion.
(It) is an object of the present invention to provide a cement additive, and a cement composition comprising the cement additive, that allows efficient use of industrial waste, and that allows producing a hardened cementitious material having good durability (sulfate resistance), by inhibiting monosulfate formation in the hardened cementitious material.
The ... invention ... enables efficient use of industrial waste, allows inhibiting monosulfate formation in a hardened cementitious material, and allows achieving good durability (sulfate resistance) in the obtained hardened cementitious material by preventing sulfate expansion in the hardened cementitious material.
Preferably, the cement additive in the above invention ... comprises calcium carbonate, gypsum, and coal ash ... as the industrial waste; calcium carbonate as the industrial waste and/or calcium carbonate not as the industrial waste; and gypsum as the industrial waste ... .
(The resulting reactions afford) good durability (sulfate resistance) and good strength development in the hardened cementitious material.
In the (invention), preferably, the cement additive comprises at least the coal ash, and the calcium carbonate is blended in an amount of 0.5 to 160 parts by weight and the gypsum (anhydrous basis) is blended in an amount of 5 to 150 parts by weight relative to 100 parts by weight of the total of the coal ash ... .
(A wide range of Coal Ash content ratios seems admissible; from a little to a lot.)
(The) invention allows effectively inhibiting monosulfate formation in the hardened cementitious material even when the calcium carbonate content in the cement additive is equal to or smaller than the gypsum content, thus affording good durability (sulfate resistance) and good strength development in the hardened cementitious material. The cement additive of the above invention may comprise at least coal ash, and may or may not comprise blast-furnace slag powder.
(Again, only Coal Ash is really required. The "blast-furnace slag powder" isn't necessary.)
In the (invention) the cement additive contains limestone powder as the calcium carbonate.
The present invention provides also a cement composition comprising the cement additive according to the above inventions. Hardening a cement composition of such an invention allows effectively inhibiting monosulfate formation in the obtained hardened cementitious material, and allows achieving good durability (sulfate resistance) and good strength development in the hardened cementitious material. Such a cement composition allows also inhibiting alkali-aggregate reaction in the obtained hardened cementitious material, and allows achieving a hardened cementitious material having good acid resistance and seawater resistance. Also, a cement composition comprising a cement additive containing at least coal ash allows reducing heat of hydration during hardening of the cement composition.
(Gosh, that old "coal ash" does a lot of good things for this "cement composition", doesn't it?)
The cement additive of the present invention enables effective use of industrial waste, and allows producing a hardened cementitious material having good durability (sulfate resistance). The cement composition of the present invention allows effectively inhibiting monosulfate formation in a hardened cementitious material obtained by hardening the cement composition, and allows producing a hardened cementitious material having good durability (sulfate resistance).
As the calcium carbonate ... limestone powder is preferred herein on account of its low cost. Limestone powder is produced by crushing (and if needed, drying and classifying) limestone, which is a natural raw material. As other kinds of calcium carbonate there may also be used crushed dust of shells, coral or the like having calcium carbonate as a main component, or processed products of the foregoing.
As the gypsum there may be used, for instance, ... industrial waste in the form of flue-gas desulfurization gypsum ... .
As coal ash there may be used industrial waste such as fly ash, clinker ash or the like. These may be used singly or in arbitrary combinations of two or more.
When the cement additive of the present invention contains at least coal ash, preferred blending ratios of the various raw materials in the cement additive are 0.5 to 160 parts by weight of calcium carbonate, and 5 to 150 parts by weight of gypsum (anhydrous basis) relative to 100 parts by weight of the total of coal ash ... .
When the cement additive of the present invention contains at least coal ash, the blending ratios (weight basis) of calcium carbonate and gypsum in the cement additive are not particularly limited, but the content of calcium carbonate and the content of gypsum are preferably substantially identical. Preferably, the blending ratio of gypsum to calcium carbonate (weight basis) is of 1:0.1 to 15, more preferably of 1:0.3 to 10, and yet more preferably of 1:0.5 to 5. A blending ratio of gypsum to calcium carbonate within the above ranges allows more effectively inhibiting monosulfate formation in the hardened cementitious material.
(The full Disclosure, as immediately above, goes into a great deal of detail about blending ratios of the various components, relative to other variables. We didn't think such detail was really warranted, and aren't producing any of it here. It might be of value to Concrete blenders dealing with specific applications.)
Besides calcium carbonate, gypsum, and coal ash ... the above-described cement additive of the present invention may also contain various types of slag such as urban-waste molten slag, steelmaking slag, sewage sludge molten slag and the like, and may contain also various kinds of incineration ash such as urban-waste incineration ash or the like.
(Interesting that they should mention "sewage sludge molten slag". See our report of:
West Virginia Coal Association | Coal Ash and Sewer Sludge to Lightweight Concrete Aggregate | Research & Development; concerning: "United States Patent 5,342,442 - Lightweight Aggregate from Flyash and Sewage Sludge; 1994; Assignee: Wisconsin Electric Power Company; Abstract: A method is shown for producing a lightweight aggregate by treating flyash and sewage sludge. Our invention involves the mixture of sewage sludge with flyash, agglomerating the mixture such as by pellitizing, and indurating the agglomerated mixture in a rotary kiln. The resultant nodular product, after cooling, can be used as a lightweight aggregate for concretes, masonry, or insulation purposes”.)
The cement additive of the present invention may be added to cement to yield a cement composition. No particular limitation is imposed on the cement to which there can be added the cement additive of the present invention, which can be added to any cement. Specific examples of such cement include, for instance, Portland cements such as ordinary Portland cement, high-early strength Portland cement, moderate-heat Portland cement, low-heat Portland cement; blended cements such as blast furnace slag cement, fly ash cement; and cements (eco-cements) comprising gypsum and a pulverized product of a combustion product produced using urban-waste incineration ash and/or sewage sludge incineration ash as raw materials. Using eco-cement as the cement is preferable as it allows increasing waste usage.
Preferably, the content of cement additive (cement proportion) in the cement composition is 90 wt % or less, in particular 5 to 70 wt %. When the content of the cement additive in the cement composition exceeds 90 wt %, the strength development and/or durability of the obtained hardened cementitious material may be impaired. The cement additive of the present invention and a cement composition comprising such a cement additive allow using large amounts of industrial waste.
(A) cement composition comprising a cement additive containing at least coal ash allows reducing heat of hydration. Inhibition of the alkali-aggregate reaction is believed to be the result of, among other factors, alkali ion fixation and/or structure compacting by the coal ash ... contained in the cement additive, while inhibition of chloride ion penetration appears to arise, among other factors, from chloride ion fixation and/or structure compacting by the Al2O3 in the coal ash ... .
As described above, the cement additive of the present invention and a cement composition comprising such a cement additive allow improving the sulfate resistance of an obtained hardened cementitious material and inhibiting the alkali-aggregate reaction, and penetration of chloride ions, in the hardened cementitious material. The cement additive of the present invention and a cement composition comprising such a cement additive allow also improving acid resistance in a hardened cementitious material obtained by hardening the cement composition.
Also, a cement composition comprising a cement additive containing at least coal ash allows reducing heat of hydration. Inhibition of the alkali-aggregate reaction is believed to be the result of, among other factors, alkali ion fixation and/or structure compacting by the coal ash ... , while inhibition of chloride ion penetration appears to arise, among other factors, from chloride ion fixation and/or structure compacting by the Al2O3 in the coal ash ... contained in the cement additive.
Industrial Applicability: The cement additive and the cement composition of the present invention are useful for efficient use of industrial waste, and are useful in the production of a hardened cementitious material having good durability (sulfate resistance)."
---------------------------
Our excerpts, and we apologize, might be a little over-long; but, we wanted to emphasize the point that a very major international producer of Cement and Concrete has established quite specific guidelines for the use of Coal Ash, and of Coal flue gas scrubber Gypsum, in the making of a Concrete, through the intermediate production of what they label a "cement additive", that outperforms standard Portland Cement Concrete in a number of key areas critical to maximizing the value of our investments in Concrete infrastructure.
The fact, that, as in our citation of "United States Patent 4,256,504 - Fly Ash-based Cement", such Coal Ash Cement compositions are likely to cost less, as well, would serve to maximize the value of those investments even further.
And, again it is clearly demonstrated, that, the solid residua resulting from our economically essential use of Coal in the generation of truly abundant and genuinely affordable electric power comprise a valuable mineral resource.
While sparing virgin resources from extraction, Coal Ash enables the production, at lower costs, of better, stronger, corrosion-resistant and more durable, Cement and Concrete.