Cement

a well known building material. Its use was known to the Egyptians 4000 B. C. It differs from lime in that it contains an additional ingredient in the shape of a fine clay. Hydraulic lime is really a cement. The most famous cement is made by first grinding a fine clay and a pure limestone or chalk into a powder, and then burning the mixture at a high temperature. It is shipped in sacks or barrels, and requires to be kept dry. When mixed with sand and water it sets or hardens, even under water, into a drab, stone-like mass resembling in color, at least, a building limestone much quarried at Portland, England, whence the name of Portland cement.

This cement is entirely artificial. The first patent was taken out in England in 1824, but the industry soon spread to France and Germany. In America the making of Portland cement got footing at Coplay, Pennsylvania, in 1878. Pennsylvania still leads the Union with an annual product of 8,000,000 barrels. Michigan, New Jersey, New York, Illinois, and Nebraska follow in the order named. A portion of the demand is met by importations from England and Germany. Of late artificial foundations and trimmings, made of Portland cement, sand, and gravel well concreted, are growing in favor and create an increased demand for it. Artificial blocks of concrete are coming into use also for walls. It is predicted freely that cement in these forms will take the place of brick. In the San Francisco earthquake of 1906 buildings having a steel frame filled with cement blocks stood the test well.

The center of the Portland cement producing industry in this country is the Lehigh district of Pennsylvania and New Jersey. In 1903 these two states produced a total of 12,447,694 barrels out of a total of 30,000,000 barrels for the entire United States. The cement output of the United States had increased in 1908 to 40,000,000 barrels. The cement rock of this region is derived from Trenton limestone.

See Brick; Pottery; Clay; Lime; Stucco; Plaster Of Paris; Glue