PORTLAND CEMENT MATERIALS

Portland cement is the most important hydraulic cement in the United States today. The use of this material has developed to such an extent that the total production of Portland cement is exceeded in value by only a few other manufactured products. The industry stands third as a consumer of coal. The manufacturing of Portland cement is not centralized, as is the case of steel manufacturing and other industries, but is distributed throughout the country on the basis of the availability of limestones and clays, cheap fuel, transportation, and markets. There are approximately 130 cement plants in operation in this country today.

Portland cement is obtained by burning to the point of fusion, a mixture of limestone and clay which contains definite proportions of lime, silica, alumina, and iron-oxides. The clinkers formed by this fusion are finely ground and the powdered material is marketed. In the burning of the raw material, calcium silicates and a calcium aluminate are formed. Reduction of the clinker to powder allows a speedy and intimate mixture with water, which is necessary, for the setting properties of the cement depend upon a reaction which will only take place in the presence of water.

When Portland cement "sets," the compounds which were formed by burning, liberate gelatinous silica and aluminate when mixed with water. The hardening of these gelatinous materials binds the filling material and renders the cement hard and strong. As the success of this cement is therefore dependent upon the formation of definite chemical compounds, it is clear that the materials utilized in its manufacture must conform in composition to definite chemical analyses.

The raw materials for manufacture of Portland cement should contain about 75% calcium carbonate or lime, and the balance clay. Not more than 5% or 6% of magnesium carbonate should be present, and alkalies and sulphates should not exceed 3%. Chert, flint, or sand in any amount are undesirable. The ratio of Al:O1 to SiO: should be about 1:3.

The following analyses are taken from the U. S. Geological Survey Mineral Resources for 1907.

According to one authority* cements of good quality usually have a composition within the following limits:

This tabulation is the result of chemical analysis which gives the percentage of each component present, but it does not indicate the nature of the chemical combinations of the components as they occur in Portland cement.

Several factors act as controls in the Portland cement industry, viz: Limestone beds relatively free from impurities other than clay, clay with a silica content between 55% and 70%, cheap fuel for burning the cement mixtures, transportation facilities, and a market for the product.

Cement is rather heavy and bulky in proportion to its value, so that a nearby market is almost necessary, and no plant can be operated at a profit where relatively cheap methods of transportation are not available.

Practically the only available localities for Portland cement manufacture in the Coastal Plain section of Arkansas are confined to the outcropping chalk deposits of the Whitecliffs area, the Foreman area, the Saline Landing area, and possibly the chalk-marl deposits in the Washington, Okolona and Deciper areas. (See "Chalk.")

Clays must frequently be transported to these areas from nearby Tertiary beds, because the clays adjacent to the chalk usually contain too much silica to yield a first class Portland cement.

Coal from the Arkansas or Oklahoma fields is available for fuel, as is the fuel oil from Arkansas, Oklahoma, and Texas oil fields. The Arkansas Natural Gas Company mains run within twenty-five. miles of White Cliffs. Both White Cliffs and Foreman are located on railway lines.

p. 271.

The Paleozoic section of Arkansas contains several extensive

G. A. Rankin, "Portland Cement," published in "Chemistry in Industry," Vol. 2,

limestone beds that can well be considered as good Portland cement material, viz: The Pitkin limestone and Boone formation of Mississippian age, St. Clair limestone of Silurian age, the Polk Bayou and Izard limestones of Ordovician age. The reader is referred to geologic maps and specific references made in the bibliography at the end of this discussion for information relative to the outcrops of these formations. In general, one or more of these limestones are available throughout northwestern Arkansas. Shales are usually present near these limestones, but cheap fuel, and markets for the product, sometimes make a difficult situation.

In northern Arkansas two localities appear as possibilities for the development of a Portland cement industry, viz: The region west of Batesville on the Missouri Pacific Railroad, and the region in the vicinity of Fayetteville. These areas possess the necessary lime and shale and are fairly well located for fuel supplies. The Batesville area is not far removed from the Southern Illinois coal fields and the transportation facilities and markets seem favorable. The Fayetteville area is close to the Arkansas-Oklahoma coal fields and is about thirty-five miles north of the west Arkansas gas fields, and transportation and market conditions seem good.

The following analyses of Arkansas chalks is taken from page 735 of the Twenty-second Annual Report of the U. S. Geological Survey, Part III, by Joseph A. Taff:

*By chemists of the U. S. Geological Survey.

"Insoluble" refers to insoluble in HC1. The other columns refer to the soluble portions only.

At present Arkansas imports all of the Portland cement used in the State, which in 1923 amounted to 848,509 barrels. With the natural occurrences of the raw materials used in the manufacture of this material so abundant and available, Arkansas is practically sure to become a manufacturer and exporter of Portland cement.

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REFERENCES TO ANALYSES

Rocky Comfort Area

Southwest quarter of the southwest quarter of Section 32, Township 12 south, Range 32 west, two miles southwest of Rocky Comfort. White chalk near the middle of the chalk formation.

Northeast quarter of the northeast quarter of Section 30, Township 12 south, Range 32 west, two miles west of Rocky Comfort. The chalky marl immediately below the white chalk.

Rocky Comfort, Little River County, near the northeast corner of the northeast quarter of Section 28, Township 12 south, Range 32 west, from lower middle part of the white chalk formation.

Same locality as No. 3, from the lower part of the white chalk formation.

Whitecliffs Area

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Northeast quarter of the northeast quarter, Section 35, Township 11 south, Range 29 west, top of the lower sandy marl bed beneath the white chalk.

Chalk bluff, Whitecliffs Landing, near the middle of the bluff in the lower part of the white chalk.

Chalk bluff, Whitecliffs Landing, fifteen feet above the base of the purer white chalk.

Chalk bluff, Whitecliffs Landing. White chalk ten feet below the top of the cliff.

Cement works Whitecliffs Landing. Average of the lower thirtyfive feet of the purer white chalk in the quarry at the cement works.

Saline Landing Area

Saline Landing, Howard County. Section 35, Township 11 south, Range 28 west, from the middle of the chalk bluff.

Northwest corner of the northeast quarter of the southwest quarter of Section 30, Township 11 south Range 27 west, white chalk from very near the top of the chalk formation.

Near the center of the southeast quarter of the southwest quarter of Section 21, Township 11 south, Range 27 west, from near the midIdle of the white chalk.

Near the base of the knoll one mile north, fifteen degrees east from Saratoga, Ark. Chalky blue marl 100 feet above the top of the white chalk.

Near the center of the east side of the southwest quarter of the northwest quarter of Section 22, Township 11 south, Range 27 west, from the lower part of the white chalk.

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Bibliography of Portland Cement Materials

1888

Branner, J. C., "The Neozoic Geology of Southwestern Arkansas."Annual Report of the Arkansas Geological Survey for 1888, Vol. II. Now out of print, but may be consulted in public or scientific libraries.

1897

Branner, J. C., "The Cement Materials of Southwest Arkansas."Transactions of the American Institute of Mining Engineers, 1897, Vol. XXVII. Obtainable from American Institute of Mining Engineers, 29 West 39th Street, New York City.

1905

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Eckel, E. C., "Portland Cement Resources of Arkansas."-Bulletin No. 243 of the U. S. Geological Survey, pp. 88-116. Now out of print, but may be consulted in public or scientific libraries.

Fitzhugh, G. D., "The Portland Cement Materials of Southwestern Arkansas."-Engineering Association of the South, Transactions, Vol.

XV, 1905.

1913

Eckel, E. C. "Portland Cement Materials and Industry in the United States (with Contributions by Burchard and Others)."-Bulletin No. 522 of the U. S. Geological Survey. Now out of print, but may be consulted in public or scientific libraries.

1924

Drake, N. F., "Mineral Fertilizers in Arkansas."-Obtainable from the Bureau of Mines, Manufactures and Agriculture, State Capitol Building, Little Rock, Ark.