The invention of the twisted bar for rein forcement was made in 1885 by Ernest L. Ran some, of San Francisco, and about 1890 came the introduction of expanded metal and the mesh systems of concrete construction, which allowed architects to retain their steel struc tures and use concrete for the filling and arch work between beams, in place of brickwork and terra-cotta. These methods enabled the archi tects to use concrete in a conservative manner, and to become acquainted with its structural properties, without abandoning the steel frame which constituted the main structural basis of their design. Between 1890 and 1895, the pro duction of Portland cement progressed from 335,000 barrels to 990,000 barrels; and the les sons learned from the use of concrete in this type of combination with steel led to its adop tion in a large number of projects originally planned for other material.
In 1897 and 1898 occurred a great shortage in structural steel, which gave directly a great additional stimulus to the adoption of reinforced concrete, and indirectly contributed enormously to the expansion of the Portland cement indus try.. Deliveries of shapes were so uncertain and remote that engineers throughout the country were at their wits' end to find ways and means for fulfilling their designs, and they turned at once to reinforced concrete to help them out of their dilemma. European systems of reinforced concrete were introduced, and engineers gener ally began to study the subject from a scientific standpoint, with the result that by the year 1900 the steel concrete building was generally recog nized as a structural possibility, and the adop tion of reinforced concrete was considered for every conceivable kind of problem.
The statistics of Portland cement production during the years that immediately preceded and followed the opening of the new century, demon strate in an astonishing way the increasing pop ularity of concrete and the confidence of the pub lic in its properties. Between 1896 (when the production of American Portland cement first passed the million barrel mark) and 1908, the country's annual output increased fifty-fold. The 26 plants operating in 1896 grew in number during the following decade to over 1.00, repre senting an invested capital of more than $100, 000,000. The phenomenal development of the industry will perhaps be best apparent from a glance at Table II, giving statistics of produce lion from 1896 to 1908. See also page 318.
Analysis of these figures shows that the out put of Portland cement in the United States has multiplied itself nearly ten times in as many years—a truly marvelous growth. The greatest single gain was in 1906, when the production increased over 11,000,000 barrels, and its valua tion $17,000,000, over the year preceding. With
in a period of five years ending in 1908, the pro duction was more than doubled, the increase in valuation being proportionate. The output dur ing the last four years alone of this period ex ceeded by nearly 75,000,000 barrels the entire production credited to the thirty years preced ing; and the valuation of the product for the same period was over $70,000,000 in excess of the value of the entire production from 1870 to 1904. An examination of the statistics also shows a gradual downward trend in the prices of the finished product.
The prodigious growth of Portland cement manufacturing, especially during the past five years, has been unequaled elsewhere in the an nals of American industrial development. No other industry has advanced with such mighty leaps and bounds in the same or a proportionate length of time.
But even these colossal figures show but lit tle of the depth or extent of public interest that has been aroused in the subject of cement and concrete construction. Even in periods of busi ness depression, the demand for cement in the building trades has been such as to tax the ca pacities of the mills to their utmost. Portland cement has long since passed the stage where it was regarded as suitable only for the building of underground and under-water work. It has entered aggressively the field of general con struction; and in spite of the fact that not all its structural applications and systems have yet been standardized, nor all its problems solved, it has abundantly "made good" in setting at rest all doubts as to its marvelous adaptabilities and fitness for constructive work in general. In the business and manufacturing districts and the residence streets of cities and towns, along the water-fronts of lake and ocean ports, along the railroad lines and country highways, at summer resorts, in rural villages and on the farm, struc tures of every size, shape, and style of adorn ment may now be seen in constantly increasing numbers—from the skyscraper to the one-story garage, from palatial residence to simple cottage or bungalow, from arched bridge to culvert and sidewalk and curb, from the great manufactur ing plant to the simple shop, from barn to dog kennel and hitching post—in whose construc tion cement has played a leading part. And when the constructive possibilities of this versa tile material come to be fully realized by the vast army of the agricultural and so-called "middle" classes—the substantial home-seekers and home-makers who constitute the backbone of our country—the output of the cement mills must show a still greater increase, which will dwarf even the present handsome figures of pro duction.