Herein we submit yet more documentation of the facts that Coal Ash can serve as a property-enhancing component of Portland-type Cement and, after some processing, as an additional or alternative aggregate in Portland Cement Concrete.
First, both of the Coal Ash utilization technologies we submit herein were developed by scientists in the employ of W.R. Grace and Company; who, if you are unfamiliar with them, are most definitely not an insignificant or un-credible source.
More about them can be learned via:
W. R. Grace and Company - Wikipedia, the free encyclopedia; wherein we're told, that, although surprisingly founded all the way back in 1854, in the nation of Peru, they are now headquartered in Maryland; and, are composed of "two main divisions, Davison Chemicals and Performance Chemicals. The Davison unit makes chemical catalysts, refining catalysts, and silica-based products that let other companies make products from refined crude oil. Its Performance Chemicals unit makes cement and concrete additives, fireproofing chemicals, and packaging sealants. Grace has more than 6,400 employees in nearly 40 countries, and annual sales of more than $2.5 billion".
First, as excerpted from the initial link in this dispatch, Grace tells us how Coal Ash can be utilized as an additional cementitious and reactive component, in combination with, and semi-replacement for, a reduced amount of Portland Cement, in the blending of concrete:
"United States Patent 4,210,457 - Portland Cement-Fly Ash-Aggregate Concretes
Date: July, 1980
Inventors: Vance Dodson and Lawrence Roberts, MA
Assignee: W.R. Grace and Company, Cambridge, MA
Abstract: Concretes containing Portland cement, fly ash and aggregate are disclosed which are capable of attaining high compressive strength and which contain relatively low proportions of Portland cement and relatively high proportions of a select fly ash component. The inventive concretes may be formulated as highly dense masses particularly suited for use in the manner of conventional structural concretes in buildings, bridges, dams, etc. Comparatively low density concrete masses may also be produced which are light in weight and have thermal insulation value rendering them particularly suited for use as thermal insulating components of roofs and as protective coatings for a variety of substrates.
Claims: A dry, hydratable concrete composition comprising a mixture of Portland cement and fly ash, and, in addition, aggregate in particulate form, said Portland cement and fly ash being present in a weight ratio of from 1 part cement to at least 1 part ash, said aggregate being present in an amount of at least 50 percent by volume of the total volume of the composition, said fly ash upon analysis having a total calcium oxide content greater than about 10 percent by weight, the total additive amount of SiO2, Al2O3 and Fe2O3 present in said fly ash being less than about 80 percent by weight, said fly ash further not having been first treated to promote activity prior to incorporation in said concrete composition.
(Note - with advance apologies for what will be a necessarily extended interruption - that, concerning the above Fly Ash compositional requirements, Ash from our eastern bituminous Coal might not, initially, meet those requirements. The "total calcium oxide", CaO, in eastern Ash could well be too low, and the "amount of SiO2, Al2O3 and Fe2O3" too high. We've reviewed some comparative compositional analyses, and been advised by a couple of our informal, fully-functional and much more competent, advisors, and that is, for the most part, almost certainly the case.
Discussion on how the various relative compositions of CaO and "SiO2, Al2O3 and Fe2O3" in the Ash can affect Cement and Concrete containing the Ash can be accessed via:
http://facta.junis.ni.ac.rs/
Medhat, CCR Vol. 29, The effect of fly ash composition on the chemistry of pore solution in hydrated cement pastes.pdf on jett; "The effects of fly ash composition on the chemistry of pore solution in hydrated cement pastes; Medhat H. Shehata, et. al., Department of Civil Engineering, University of Toronto, Canada"; and:
Medhat, CCR, Vol 30, The effect of fly ash composition on the expansion of concrete due to ASR.pdf on jetty.ecn.purdue.edu; "The effect of fly ash composition on the expansion of concrete due to alkali-silica reaction; Medhat H. Shehata, et. al., Department of Civil Engineering, University of Toronto; This paper presents the results from expansion tests on concrete prisms and mortar bars containing reactive aggregate and different types and levels of fly ash. Eighteen fly ashes representing those commercially available in North America were tested. The results show that the bulk chemical composition of the fly ash provides a reasonable indication of its performance in physical expansion tests but cannot be used to accurately predict the degree of expansion or the minimum safe level of fly ash required to suppress expansion to an acceptable limit. Generally, for a given fly ash replacement level (RL), the expansion increases as the calcium or alkali content of the ash increases or its silica content decreases. A corollary to this is that the minimum level of fly ash required to limit the expansion to an acceptable level increases as the calcium or alkali content of the ash increases or its silica content decreases. Most of the variation in fly ash performance can be explained on the basis of pore solution composition; those ashes effective in reducing the alkalinity of the pore solution extracted from cement paste samples were also efficient in controlling expansion. The data from this study provide further support for the use of the accelerated mortar bar test as a means for evaluating the efficacy of pozzolans in controlling expansion due to alkali-silica reaction".
The upshot is that there are trade-offs between the relative amounts of CaO and other components in the Coal Ash. Keeping in mind that CaO is a primary constituent of Portland Cement in the first place, the initial subject of our presentation herein "United States Patent 4,210,457 - Portland Cement-Fly Ash-Aggregate Concretes" actually devolves into what is known as a "Composition of Matter" patent.
See: Composition of matter - Wikipedia, the free encyclopedia.
Further, again keeping in mind that CaO is a primary constituent of Portland Cement itself, any shortfall of CaO could be made up by simply lowering the amount of low-CaO Fly Ash that is to be blended, according to the specifications of "United States Patent 4,210,457", with the Portland Cement.
Otherwise, CaO, which is, in one aspect, calcined limestone, can be added in an appropriate amount to the mix, or, perhaps more preferably, depending on location and costs of transport, Ash from relatively high-CaO, lower-SiO2, Al2O3 and Fe2O3 lignite Coal can be blended with Ash from relatively low-CaO, higher-SiO2, Al2O3 and Fe2O3 Ash bituminous Coal to achieve a balanced composition.
And, that is, in fact, as we might document in future reports, an alternative that has been proposed.)
The concrete composition ... wherein said ratio of cement to fly ash is from 1 part cement to at least 1.5 parts fly ash.
The concrete composition ... wherein said ratio is from 1 part cement to at least 2 parts fly ash.
(Note, that, as we have previously documented, Portland Cement can, depending on the composition of the specific Fly Ash, be replaced by Fly Ash on a more than one-to-one basis in Cement and Concrete mixes; and, that, perfectly acceptable Cement compositions consisting of two-thirds, and, as we will later document, even more of Coal Ash, can be blended.)
The concrete composition ... wherein said aggregate has a dry bulk density greater than about 80 pounds per cubic foot (and) comprises a mixture of coarse and fine aggregate, said fine aggregate having a particle size less than about 3/8 inch (and) wherein said aggregate comprises a mixture of sand and stone and is present in an amount greater than about 50 percent by volume of the total composition.
(Note the immediately-above summation of claims. It is of importance relative to the second United States Patent we document, further on, in this dispatch.)
The concrete composition ... to which is additionally added sufficient water to render the dry mixture plastic.
A dense, hard, hydrated concrete mass produced by addition of water to the dry mixture ... and thereafter allowing the resulting wet mixture to harden, said mass having a dry density greater than about 120 pounds per cubic foot.
The concrete composition ... wherein said aggregate is selected from the group consisting of gravel, granite, limestone, shale, silica sand, and mixtures thereof.
The concrete composition ... wherein said aggregate has a dry bulk density of less than about 15 pounds per cubic foot.
(Note the above two, widely-varying, specifications for aggregate; which cover both normal- and light-weight Concrete, as Grace goes on to specify in some detail; and, both of which can be, as we will see, satisfied through the utilization of even more Coal Ash.)
Background: This invention relates to cementitious compositions containing Portland cement and fly ash. More particularly, this application concerns novel Portland cement concrete compositions containing relatively low proportions of cement together with relatively high proportions of a select fly ash component, which compositions when mixed with water and allowed to set harden into masses exhibiting unexpectedly high compressive strengths.
Summary: It has been found that certain fly ashes when combined with Portland cement in weight ratios of 1 part cement to 1, preferably about 1.5 parts fly ash up to weight ratios of 1 part cement to about 15 parts fly ash produce surprisingly high strengths in concrete, mortar and pastes which it is believed, cannot be entirely accounted for by the conventional "pozzolanic reaction". The fly ashes combined with Portland cement in these relatively high ratios to produce unexpectedly high strength mixtures according to the invention are those characterized as having a total analyzable calcium oxide greater than about 10, preferably greater than about 15, percent by weight and a combined silica (SiO2), alumina (Al2O3), and iron oxide (Fe2O3) content of less than about 80, preferably less than about 75, percent by weight. Particularly valuable are high density mixtures of such cement/fly ash combinations with aggregate such as sand and/or stone to produce structural concretes where strength is most important. These "structural" concretes according to the invention exhibit high strength when measured at early as well as later stages of hydration with minimum cement content. A practical result of the invention is the ability to formulate high strength structural Portland cement concrete mixes containing less Portland cement than conventional Portland cement structural concrete mixtures."
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Which immediately-above results would lead not only to the profitable, and immensely beneficial, utilization of a widely-vilified byproduct arising from our essential use of Coal in the generation of economical electric power; but, since it would result in a reduction in demand for Portland Cement, would also reduce Carbon Dioxide emissions from the combined process of Coal-fired power generation and Portland Cement manufacture, which, in the calcination of limestone to produce Cement, generates Carbon Dioxide according to the equation CaCO3 + Heat = CaO + CO2.
In any case, to make Concrete for use in any genuinely structural applications out of any type of Cement requires the addition of aggregate, i.e., the "gravel, granite, limestone, shale, silica sand, and mixtures thereof" noted in the Disclosure of "United States Patent 4,210,457 - Portland Cement-Fly Ash-Aggregate Concretes".
And, W.R. Grace has that base covered, as well, through the use of Coal Ash; as seen in:
"United States Patent: 4336069 - High Strength Aggregate for Concrete
Date: June, 1982
Inventors: Vance Dodson and Lawrence Roberts, MA
Assignee: W.R. Grace and Company, Cambridge, MA
Abstract: Concretes containing a hydratable cementitious binder such as Portland cement and a high strength aggregate material are described. The high strength aggregate material is produced from hydrated cementitious compositions which contain relatively low proportions of Portland cement and relatively high proportions of a select fly ash component. The high strength aggregate material is produced by mixing the aforementioned Portland cement and fly ash components with water and allowing such to hydrate. The hydrated aggregate product may then be reduced in size (e.g. by crushing) and screened prior to combination with the cementitious binder to produce concrete compositions. Concretes can be prepared with such aggregate which have at least comparable compressive strengths to concrete prepared using conventional crushed stone aggregate.
Summary: It has been found that a strong aggregate meeting the above requirements and suited for use in preparing concrete compositions can be prepared from hydrated mixtures of Portland cement and a select fly ash component described in our previous U.S. Pat. No. 4,210,457.
(As reported above, we perhaps unnecessarily point out.)
Aggregate suited for use in concrete can be prepared from such hydrated mixtures, for example by crushing or otherwise reducing the size thereof, followed optionally by screening to give a desired particle size. Alternatively, aggregate from such hydrated mixtures can be produced in a manner which makes crushing unnecessary. For example, non-hydrated or partially hydrated particles of the desired size can first be formed by known methods of pelletizing, etc., followed by complete hydration to produce the high-strength aggregate. The aggregate produced according to the invention is thereafter mixed with any of the conventional hydratable cementitious binders used in concrete, and also water, and thereafter allowed to hydrate or "cure" to a hardened "concrete" mass of high strength. Any of the conventional additives used in concrete can be used in the concretes produced from the aggregates of the invention. For example, chemicals may be included to regulate setting time, to enhance strength, to entrain air, etc. Also, additional aggregate of the conventional type such as sand, etc., can be included in the concretes produced according to the invention."
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We acknowledge that, as seen for one instance in:
Consol Converts Coal Ash to Concrete Aggregate | Research & Development; concerning: "United States Patent 5,364,572 - Process for Making High-Strength Synthetic Aggregates; 1994; Assignee: Consolidation Coal Company, Pittsburgh; Abstract: A process for making high-strength aggregates including hydrating calcium oxide containing coal combustion ash for a sufficient period of time to convert a high percentage of the calcium oxide to calcium hydroxide prior to forming the aggregates and curing the aggregates in high humidity. The moisture of the hydrated material is monitored to vary the hydration moisture to the desired set point. Further, the process involves producing high-strength aggregates from calcium hydroxide containing FGD ashes such as generated from duct sorbent injection and spray dryer processes";
the use of Coal Utilization Byproducts in the making of high-strength Concrete aggregate is not unknown among people who trouble themselves to look into the matter.
But, in conclusion, note, according to "US Patent 4,210,457 - Portland Cement-Fly Ash-Aggregate Concretes", that, we can make a superior Concrete out of a Cement blend composed "of 1 part cement to 1, preferably about 1.5 parts fly ash" and "aggregate (which) is present in an amount greater than about 50 percent by volume of the total composition" and, which aggregate, according to "US Patent 4,336,069 - High Strength Aggregate for Concrete", can itself be made out of more Coal Ash.
We've previously documented how much Portland Cement, and how much Concrete aggregate, is manufactured, quarried and consumed on a yearly basis in the United States of America.
And, the import of it all is, that, if we would just get off our cans and get to work doing the sensible things that need doing, we would wind up with a significant, profitable business supplying the Cement and Concrete industries with the solid byproducts arising from our, to beat it to death, absolutely essential use of Coal in the generation of economical electric power; a business so robust, that, based on our analyses of the published numbers, we would not only consume and utilize all of the solid byproducts currently arising from our essential use of Coal in the generation of genuinely economical electric power, but, might well be compelled to start "mining" older deposits of those products that have, in previous generations, been stockpiled, land filled or otherwise shoved to the side.
We might have our work cut out for us; but, we miners of Coal aren't afraid of a little hard work, are we?
We're not really expecting pennies to rain down on us from the clouds, or, to waft up to us all through some little old holes carpetbaggers are poking into the shale, are we?
If so, then, to our great sorrow, all of our work here over the past years has certainly been wasted