American Portland cement has practically displaced the imported article. New uses have been found for Portland cement and it is coming rapidly to the front as a material of construction. The new American Association of Portland Cement Manufacturers formed in 1902, promises to do wonders for the industry and to the end of showing the many uses to which Portland may be applied with advantage, erected a building and prepared an exhibit for the Louisiana Purchase Exposition at St. Louis during 1904. Tables III, IV and V show the growth of the American Portland Cement industry and Table VI gives a graphic comparison of the imports, production and consumption of Portland and Natural cements from 1890 to 1903. TABLE III.-TOTAL PRODUCTION OF PORTLAND CEMENT IN THE UNITED STATES, 1870 TO 1904. (Mineral Resources of United States.) TABLE IV.-PRODUCTION OF PORTLAND CEMENT IN THE UNITED STATES IN 1902, 1903 AND 1904, BY STATES. (Mineral Resources of United States, 1904.) Alabama Arkansas.. California Georgia Illinois Indiana Kansas Kentucky Michigan. Missouri New Jersey New York. Ohio Pennsylvania South Dakota. Texas.. Utah Virginia. West Virginia. a The production of Alabama and Georgia is combined with Virginia, the production of Missouri and South Dakota with that of Kansas, and the production of Utah with that of California. 6 The production of Alabama, Georgia and West Virginia is combined with Virginia, Arkansas is combined with Missouri, Texas with Kansas, and Utah and South Dakata with Colorado. c'the production of Alabama, Georgia and West Virginia is reported with Virginia, Missouri with Kansas, and Utah and Texas with Colorado. TABLE V.-DEVELOPMENT OF THE PORTLAND CEMENT INDUSTRY IN THE UNITED STATES SINCE 1890. (Mineral Resources United States, 1904.) CHAPTER II. THE NATURE AND COMPOSITION OF PORTLAND CEMENT. Portland cement may be defined as "the finely pulverized product resulting from the calcination to incipient fusion of an intimate mixture of properly proportioned argillaceous and calcareous materials and to which no addition greater than 3% has been made subsequent to calcination1." When the fine powder is mixed with water chemical action takes place, and a hard mass is formed. The change undergone by the cement mortar in passing from the plastic to the solid state is termed "setting." This usually requires but a few hours at most. On completion of the set a gradual increase in cohesive strength is experienced by the mass for some time, and the cement is said to "harden." Cements usually require from six months to a year to gain their full strength. Cement differs from lime in that it hardens while wet and does not depend upon the carbon dioxide of the air for its hardening. It is very insoluble in water and is adapted to use in moist places or under water where lime mortar would be useless. On pages 16 and 17 are two tables showing the analysis of various Portland cements. Composition of Cement. 2 Portland cement, according to Le Chatelier, consists of a mixture of tricalcium silicate, 3CaO.SiO2, and tricalcium aluminate, 3CaO.Al2O3. He arrived at this conclusion after a long series of experiments, which consisted in examining thin sections of cement clinker under the polarizing microscope. He also made experiments upon the synthetic production of calcium silicates and aluminates by heating intimate mixtures of finely pulverized silica, alumina, and lime. He then examined into the hydraulic properties of the compounds so prepared. He, however, failed to prepare the tricalcium silicate directly by heating lime and silica, the 1 Standard Specifications, Amer. Soc. Test. Mat. 2 Constitution of Hydraulic Mortars, (Trans. by Mack), and Annales des Mines, 1887, P. 345. |