Cement And Concrete
Soon after the construction of the Panama Canal was commenced the Isthmian Canal Commission bought from the Allis-Chalmers Company the first stone crushing plant used in the production of crushed stone for concrete work. This plant consisted of one No. 8 Style "K" and two No. 5 Style "K" Allis-Chalmers "Gates" Crushers, and the necessary auxiliary equipment. The plant was designed by the Allis-Chalmers Company and erected by the Isthmian Canal Commission near Ancon. Its capacity was about 1,000 cubic yards per day of eight hours.
Later on as the work progressed and the Gatun Locks were being constructed the government engineers decided to erect a plant at Porto Bello to produce the crushed stone required for this work. The rock in the Porto Bello Quarry was very hard and abrasive, closely resembling that found in the Palisades on the Hudson River, New York. The operations at the quarry being of necessity very large, and the additional fact that the peculiar formation of the rock caused it to blast out in pieces of immense size, made the installation of a large preliminary crusher necessary to obtain maximum operating economies. The engineers of the Isthmian Canal Commission decided upon a No. 21 Allis-Chalmers "Gates" Gyratory Crusher for this work as the most modern machine.
The great and rapid advance made in crushing machinery is shown by the size of the receiving openings of the No. 8 crusher installed at Ancon as compared with the No. 21 installed at Porto Bello. The No. 8 crusher has two receiving openings eighteen inches by sixty-eight inches, whereas the No. 21 has two receiving openings forty-two inches by 114 inches, the former machine weighting approximately fifty tons and the latter about 235 tons. To give some idea of its immense size it should be noted that it will take pieces weighing four to five tons, breaking them down to about seven inches in one operation. This large crusher is capable of easily crushing 5,000 cubic yards of rock in eight hours, although it was never extended to its fullest capacity as only 3,500 cubic yards were used at the Gatun lock daily. The enormous size and weights of the individual pieces that go to make up this machine made the transportation and installation (the plant being located several hundred feet above water level) a difficult one, and much credit is due the management and engineers of the Isthmian Canal Commission in successfully mastering these problems.
The rock in the quarry was loaded with large steam shovels into six to eight-ton side dump cars, and trains of ten cars were brought by locomotive to the crusher and discharged into the feed hopper. After being crushed in this preliminary breaker to about seven inches the material dropped into a sixty-inch Allis-Chalmers pan conveyer and elevated to additional crushers which further reduced it to about three and one-half inches. The material used in the concrete work at Gatun locks being "crusher run," no sizing screens were necessary at the crushing plant. Its location being on a hill-side, all the crushed material flowed by gravity to a final conveyer located at the foot of the hill which carried it to the storage bins. These bins were located on Porto Bello harbor, and the material was loaded directly from these bins into barges having a carrying capacity of about 700 cubic yards. The barges were towed to Gatun, a distance of about thirty-five miles, and there unloaded with clam shell buckets.
By the middle of 1909 work on the locks had reached the state when concrete construction began in earnest, and immense quantities of material were accumulated at Gatun, Miraflores and Pedro Miguel. The extraordinary size of the culverts and other conduits connected with the locks make it necessary that specially designed forms should be employed for the deposit of concrete. Experience in the construction of such works as the New York subways had demonstrated the superiority of collapsible steel forms over the old wooden forms. Although the first cost was higher, the steel forms proved much more economical in large operations, because of the rapidity with which work could be done.
After considerable study of the problem, the commission adopted a design furnished by the Blaw Steel Construction Company, of Pittsburgh, as being best adapted to canal work. Contracts were awarded to this company, and the forms were shipped to the Isthmus in July, 1909, and July, 1910. The accompanying illustrations give a clear idea of the manner in which the forms were used for culvert construction in the locks. The forms were of great size, measuring in some cases twenty-two feet in diameter, and were the largest in existence at that time. In the tropical climate of Panama wood forms would have warped and caused no end of trouble by losing their shapes, but the steel forms retained their rigidity under all conditions, and, or course, were no affected by tropical heat.
Instead of setting up a temporary form which would have been knocked down again with each completed section of the work, as is necessary when wood forms are used, the steel forms were merely telescoped and moved forward to a new section. No repairs or renewals were required, there was no waste labor or material, and valuable time was saved on account of the ease with which forms were set up and removed, and also on account of the accurate adjustment.
Since these steel forms were employed at Panama they have become a factor in other important concrete construction projects, notably in the aqueduct conveying Catskill water to New York City, and in the New York subways.
The steel forms furnished for the culverts through Miraflores and Pedro Miguel locks by the Blaw Steel Construction Company were ten, eighteen, twenty and twenty-two feet in diameter.
The heavy loads of concrete which these forms had to carry and the requirement that one section be passed through the others in position made it necessary to use the most advanced ideas in the design of a collapsible telescopic form.
The full round forms were made in five-foot sections, each section being divided into quadrants. The quadrants were rigidly braced with angles, making it impossible to distort the forms when handling or loading with concrete. The joint lines of the quadrants were on the horizontal and vertical planes. The horizontal joints were reinforced with lap plates spanning the joint from one quadrant to the other. At the vertical joints, top and bottom, hinges were provided for holding the quadrants together.
The moving of the forms was accomplished by means of a special traveler which ran on a track attached to the bottom quadrants. This traveler was provided with vertical jacks and side collapsing arms which engaged the top quadrants. The jacks and arms after being fastened to the top quadrants were collapsed, drawing in the quadrants to a position of less cross-sectional area than when in full position, so they could be passed through the sections in place. The bottom quadrants were collapsed by a rope and block and raised by a chain hoist to a position which would allow them to be telescoped.
The horseshoe-shaped forms were of the three hinges type. The sections were five feet long and divided into four parts called side sheets and wing plates. The side sheets were hinged together at the top and to the lower ends of the side sheets were hinged the wing plates. The collapsing and moving of these forms was done one a traveler constructed to run on a track which was laid on the finished invert of the culvert. The traveler was provided with vertical jacks and side collapsing arms. the vertical jacks engaged the forms at the top hinge joint and the collapsing arms engaged to side sheets above the joint of the wing plates. After the traveler was made fast to the forms, the wing plates were raised and folded in next to the side sheets. The side sheets were then drawn away from the concrete by the collapsing arms and the entire form lowered by the vertical jacks sufficient to pass through the forms in position.
The water passages under the floors of the locks were made with a full round form. At regular intervals an opening occurs from these water passages up into the locks. The opening was formed by a special collapsible steel form which fitted on the full round form and projected up to the floor line of the lock.
These forms were built by the Blaw Steel Construction Company from their own designs, which were approved by the United States engineers. The forms were erected in the shops and inspected before shipment. No skilled labor was required to handle them, as all parts were interchangeable, thus avoiding any cutting or fitting after the forms were erected.
The Alpha Portland Cement Company, which from time to time furnished the Isthmian Canal Commission with large quantities of cement, is one of the largest Portland cement concerns in the United States, as well as one of the pioneers in the American manufacture of Portland cement.
When the Alpha Company started operations in 1891, there was but little Portland cement used in this country. The first equipment of the company consisted merely of two forty-foot kilns, and the yearly production amounted to only 100,000 barrels-a quantity that the six great plants of the Alpha can now produce in four days.
The mills of the Alpha Company are located at Martin's Creek, Pa., Alpha, N.J., Manheim, W. Va., and Cementon, N.Y. There are six great plants on six trunk line railroads. The Catskill plant, with its private docks, is also directly on the Hudson River and ideally situated for shipments along the coast, the barge canal, and for export purposes.
The product of the Hudson River Alpha plant has a characteristic that fortunately fits with its location, that is, the low percentage of alumina in the rock, which adapts the cement particularly to use in sea-water. Extensive investigations show that a cement of low alumina content gives the best results where concrete is exposed to salt water, sewerage acids, etc. For a time only imported cements were used in the under-water construction on the Key West Coast Railroad. When Alpha cement was tested thoroughly it was found to meet every test, and thereafter was used in the under-water construction of the extension.
The Martin's Creek quarry of the Alpha Company is perhaps the best known of any of the Portland cement plants on the continent. Here are a thousand acres of the finest quality of cement rock, the face of the quarry being from 100 to 170 feet high, and the limestone possessing just the proper percentage of lime needed for a perfect Portland cement. In the blasting methods followed at the Martin's Creek quarry, holes are drilled in sets of ten to fourteen down the entire quarry face and snake holes driven in to meet the vertical borings. In the blasts as much as ten and one-half tons of dynamite are used to bring down the rock.
In addition to having been selected as one of the brands for use on the canal, Alpha Portland cement has been liberally used by the United States government in important operations, such as the fortifications at Egmont and Mullett's Keys, Forts Hancock, Wadsworth, Slocum, Monroe, Strong, Mott, Totten, and Schuyler, as well as in the Navy Yards at Portsmouth, Charleston, Brooklyn, Norfolk, League Island, and Boston. It has been also used extensively by the government for piers, sea walls, dry docks, light houses, etc. The company has recently enlarged its capacity so that now it has a procuring capacity of 9,000,000 barrels a year, and storage facilities of 2,000,000 barrels.
One of the most remarkable records during canal construction was that of the Atlas Portland Cement Company. The government used 5,000,000 barrels of the company's cement in the Panama Canal without the rejection of a single barrel. Following this record the company then practically supplied all the cement needed to supply the canal work, following its first consignment of 5,000,000 barrels with additional shipments which soon ran over the half million barrel mark, and continuing until the canal was finished. In keeping with the policy of "safety first," cement was needed at Panama which by the most rigid and extensive tests could prove its superiority. These requirements were met by the Atlas Company, and the enormous consumption of cement for the work and the possibility of loss through idle equipment and a shifted payroll in case of slow deliveries made necessary the selection of a cement manufactured where production not only met but could exceed any demands made. The Atlas Portland Cement Company, having a daily productive capacity of 50,000 barrels, or 18,000,000 barrels per year, therefore was able to cope with any demands for Panama without interfering with other shipments. The company's productive capacity was and is by far the largest in the world. The first 5,000,000 barrels furnished by the Atlas Company was used in constructing the canal locks, and Gatun dam and spillway. Because of the importance of this phase of the construction the cement was given most rigid and exacting tests in the government's laboratories, and not a single barrel was rejected for any reason. This is an incomparable record of industrial efficiency in production and one which can scarcely be paralleled by any concern in the world. It can, therefore, be readily understood why the United government when it found it would require a large additional supply of cement to complete the work decided to enter into a new contract with the Atlas Portland Cement Company to supply the cement required to complete the canal. If one could realize the magnitude of 5,000,000 barrels of cement or 5,000,000 packages of any kind, some appreciation could be reached of the feat of the Atlas Company in having this vast number of deliveries passed unchallenged by the guardians of the canal. The achievements in Panama will go down in history as monuments to those who labored there, but not the least among the achievements was the steady and uninterrupted delivery of great quantities of supplies of the highest efficiency by American industrial standards.
From: The History of the Panama Canal, by Ira E. Bennett, Historical Publishing Company, Washington, D.C., 1915, pp. 371-375.