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hold in foreign markets that when normal conditions are restored they can not be displaced.

CEMENT.

The growth of the Portland cement industry in the United States has been one of the wonders of modern industry. In 1880 there were produced in the United States 85,000 barrels of Portland cement; in 1913 the production was more than 92,000,000 barrels, valued at an equal number of dollars—the world's record of production. The comparison made graphically in fig. 6 is of interest.

1913 PRODUCTION 92,000,000 BARRELS

1

1880 PRODUCTION

85,000 BARRELS

H

FIG. 6.-Growth in annual production of Portland cement in the United States,

1880 to 1913.

The accompanying curve, fig. 7, illustrates the phenomenal increase in the output of Portland cement since 1890. This increase, it is interesting to note, did not suffer a check from its beginning.

The United States imports relatively little hydraulic cement, only 85,000 barrels having been imported in 1913. There is little or no need to import any cement, for all parts of the country are now fairly well supplied with mills for the manufacture of Portland cement, and the supply of raw materials is practically inexhaustible. A significant feature of the cement industry, however, is the fact that, though only about 80 per cent of the normal cement-producing capacity of the country is employed at the maximum, there is often an overproduction; yet the exports of hydraulic cement have scarcely

and Dollars 90,000,000

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Fig. 7.—Production of Portland cement and value of Portland cement in the

United States, 1890–1914.

exceeded 4,200,000 barrels in any year, this amount being only about 5 per cent of the total output-not sufficient to take care of the surplus production in a year of great activity.

There seem to be excellent reasons for stimulating the export trade to South America as rapidly as possible. Although the export of a relatively bulky and low-priced material such as cement may not promise large direct profits to an individual producer, yet the creation and maintenance of an export trade should benefit the industry at large through the opportunity to dispose of surplus stocks. American manufacturers have not made the most of their opportunities to build up an export trade. Exports of cement from England, Germany, Belgium, and France not only have been considerably greater than those from the United States, but have borne a much higher ratio to the production in these countries. Cement exports from France in recent years are estimated to have reached at least 23 per cent of the production, and from Germany about 17 per cent. There are few cement plants in South American countries, and in the past these countries have been supplied mainly from Europe. There is evidently an opportunity now for the cement industry of the United States to secure this trade. The extent to which we have made ourselves independent of foreign cement in times of peace is shown by the fact that 20 years ago the imports of foreign cement were more than 33 per cent of our domestic product, whereas in 1913 our imports were less than 0.1 per cent of the domestic production.

One reason for the absolutę independence of the American cement industry is that everything needed by a fully equipped cement mill may be obtained in the United States. Some pulverizing machinery has been purchased abroad, pebbles for use in grinding mills have been imported, and possibly some of the fire clay used in the manufacture of kiln linings may have been imported; but such imports are no longer necessary. Substitutes for flint pebbles, brought from Denmark and France, are least easily procured, but there are possible domestic sources of supply in Arkansas, Mississippi, Colorado, Montana, and other States. The Colorado and Montana pebbles have been used in Portland cement plants.

The rapid development of the American cement industry dates from the introduction of the rotary kiln, fired with powdered coal, about 1895. Natural gas and crude petroleum are important kiln fuels in localities where they are cheap. Notable reductions in costs have accompanied improvements in manufacturing, so that to-day Portland cement is sold for less than one-third of its price in 1880. The reduction in price is graphically shown in the curve, fig. 8.

The facility with which Portland cement concrete is handled and its adaptability to a wide variety of uses has made possible great developments in public works. The invention of processes that render concrete practically waterproof is a long step toward a still wider use. The use of cement concrete on the farm seems to have almost unlimited possibilities. Mining work is requiring increased quantities of cement

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Fig. 8.-Range in average price per barrel of Portland cement, 1880-1913.

and concrete for surface structures, shaft linings, and roof supports, where it replaces wood. In the rapid development of concrete construction utility has naturally received greatest attention. The

artistic possibilities of concrete are now beginning to receive a fair share of attention.

Although Portland cement was invented early in the nineteenth century by Joseph Apsdin, of Leeds, England, the greatest development in methods of manufacture and quality of product has really taken place in the United States since 1890. To-day the superiority of practically all the American Portland cements is recognized throughout the world. In part this recognition is an outcome of the United States Government specifications that practically all cements must pass, as they are used on Government works.

One of the present needs of the cement industry is for a comprehensive survey of available supplies of sand and gravel for use with Portland cement for concrete construction-especially for concrete roads. These are materials the distribution of which counts for most in determining their economic value.

ASPHALT AND ALLIED BITUMENS.

The marketed production of natural asphaltic material in the United States in 1913 aggregated 93,000 short tons, valued at $751,000. In 1882 the entire output of asphaltic material in the United States came from a single locality in California and amounted to about 3,000 tons, valued at $10,500.

Imports of natural asphalt for consumption in the United States are at present almost wholly from Trinidad and Venezuela, the quantity brought in during the fiscal year ending June 30, 1914, aggregating 181,000 long tons, valued at $918,000.

Exports of asphalt (largely oil asphalt) from the United States in the same period amounted to 50,000 long tons, valued at $1,131,000, and in addition asphalt products manufactured in the United States, amounting in value to $362,000, were exported. Exports of crude asphalt were chiefly to Canada, Germany, West Indies, Great Britain, Argentina, and Brazil.

Oil asphalt is manufactured from petroleums produced in the Gulf coast fields and in California, as well as from petroleum of the same general type imported from Mexico. In 1913 some 437,000 short tons of oil asphalt, valued at $4,500,000, were manufactured in the United States from petroleum of domestic origin, and in addition some 114,000 tons, valued at $1,700,000, were manufactured from petroleum of Mexican origin. The utilization of the Mexican petroleum for this purpose is purely a matter of convenience in refining the petroleum, since ample supplies of suitable petroleum are available in the Gulf coast, Illinois, Wyoming, and California fields.

Natural asphaltic rock occurs in the United States in western Kentucky, southern Oklahoma, western Texas, California, and Utah, and has recently been discovered in large quantities in the Philip

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