The Maufactufe and Uses of Portland Cement

By T. K. Partridgg Sales Manager Southwestern Portland Cement Co., Los Angeles

The need of the word "Portland" in connection with this subject is, perhaps, superfluous. However, to clarify the minds of the readers it may be of interest to explain why practically all cements marketed in this country are called "Portland."

Although the builders of ancient times were unable to perform the feats of construction made possible by Port- of Portland, that he gave it the name "Portland Cement."

While it is a fact that some very high grade natural cement was made in the State of New York at about this same time, the developments abroad of the accurately-controlled manufactured Portland Cement led to rather large imports of that product as being stronger and more dep.trdrbl., and uliimately brought about the -beginnittg.gf ihe Portiand Cement Iidustry in the United States with the establishment of a small riritt at Coplay, Pennsylvania, in the vear L872.

From this small beginning the industry ha9 grown steadily until there are now scattered throughout the United States upwards of 150 mills, representing an-inves-tment of oler $300,000,000 and producing approximately 150,000,000 barrels per year.

Not until about fgOO-naa this country's production surpassed the sale of the imported article. However, the past Quarter of a century has brought so many improvements in rirethods of manuficture and interested additional capital to such an extent that today the mills of the United States are producing more Portland Cement than all other countries of the world combined.

T. K. Partridge.

land Cement and modern methods, it is a certainty that the knowledge of a bonding or cementing material has been in the possession of rnan since the dawn of history as evidenced by the pyramids of Egypt.

The remarkable- ruins of ancient civilization manifest clearly the fact that both the Romans and Carthaginia-ns built itructures of concrete. Probably the oldest examples that have been preserved of hydraulic cement concrete are the still standing supporting arches of a seventy-mile aqueduct which was one achievement of the Carthaginians.

The Romans of ancient times used slaked lime mixed with volcanic ash and found it a very superior building material, although apparently not understanding the proportioning of the materials, nor the part the volcanoes had played in burning the rock. - Att of these early cements were hydraulic or natural, depending mainly upon nature for their formation.

The credit for inventing Portland Cement is given to Joseph Aspdin, a mason of Leeds, England, who patented in L824 a product resulting from burning and pulverizing an artificial mixture of slaked lime and clay.

Concrete made from this product resembled so much in color, hardness and durability the Portland building stone, then popular in England, which was quarried on the Isle

At this point it would be of interest to state that while the unit of computation is usually on the "barrel" basis, as a matter of facC the packing generally used is a sack. Th. method of filling the sack itself is decidedly novel. The empty sack is first tied. Then it is hung upside down with a discharge nozzle of a packing machine-inserted in a small opening at one corner of the sack. Cement is forced in by rapidly revolving paddle wheels in the machine until 94 pounds have been pushed in. Then the flow of cement is automatically cut off. When the sack is turned right side up, the weight of the cement pressing against a flap of cloth fasterled along the hole forces it against the sack, effectually closing the opening. This is known as the Bates Valve Sack. Four sacks weighing 376 pounds net make up the "barrel" unit.

It is well to bear in mind the fact that Portland Cement differs from Natural Cement in that it is a strictly manufactured product and in order to realize what a carefully controlled process is followed I might refer to the Specifications as adopted by the United States Government or the following technical definition worked out by the American Society for Testing Materials which is accepted as standard: "Portland Cement is the product obtained by finely pulverizing clinker produced by calcining to

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