The cut in Plate 26 will no doubt be of much interest as showing the great versatility of con crete blocks and the many purposes for which they are now used which were probably not dreamed of in the earlier stages of the industry. The smokestack shown is located at Cooks Ferry pumping station of the Southwestern Pennsyl vania pipe lines. It is 120 feet over all, and has an inside diameter of 4 feet. It is lined with an inner shell of firebrick laid up in fire clay for a distance of 45 feet, while the remaining dis tance is not lined in any way.
The smokestack is reinforced with both vertical and horizontal steel rods, the vertical rods extending into the foundation, where they branch out like the roots of a tree and extend clear to the top of the smokestack. The horizontal reinforcing consists of rings laid in the joints between each layer of blocks; these are well lapped and are wired to the vertical rods.
The blocks are made solid with recesses for engaging the reinforcing bars. The bottom of foundation is 8 ft. below ground grade, and is 18 ft. square. The founda tion and octagonal part of the stack were built in place with wooden forms, and are heavily reinforced, while the remaining or round portion of the chimney was built of solid concrete blocks.
Iron smokestacks have been replaced by con crete in a novel manner at the plant of the Cana dian-Portland Cement Company, at Marlbank, Ontario. At this plant, four stacks, each 60 feet high and 4 feet in diameter, lined inside with one thickness of firebrick, recently showed signs of corrosion in the plates. Instead of replacing with iron or steel, it was decided to coat the out side of each stack with a 4-inch layer of concrete. For this purpose a plate-iron cylinder 56 inches in diameter and 48 inches high was used as a form, and moved up the stack as the concrete, which was deposited within it, had set. Circum ferential reinforcement of No. 7 wire was placed every vertical six inches in the middle of the 4-inch thickness. It is estimated that about $1,200 was saved in the construction by concrete covering, above the cost of new iron or steel stacks.
Mr. Sanford E. Thompson gives the following rules to be followed in the construction of rein forced concrete chimneys: Rules for Design of Concrete Chimneys 1. Design the foundations according to the best engineering practice.
2. Compute the dimensions and reinforcement in the chimney with conservative units of stress, providing a factor of safety in the concrete of not less than 4 or 5.
3. Provide enough vertical steel to take all of the pull without exceeding 14,000, or at most 16,000 pounds per square inch.
4. Provide enough horizontal, or circular steel to take all the vertical shear and to resist the tendency to expansion due to the interior heat.
5. Distribute the horizontal steel by numerous small rods in preference to larger rods spaced farther apart.
6. Specially reinforce sections where the thickness in the wall of the chimney is changed or which are liable to marked changes of temperature.
7. Select first-class materials and thoroughly test them before and during the progress of the work.
8. Mix the concrete thoroughly, and provide enough water to produce a quaking concrete.
9. Bond the layers of concrete together.
10. Accurately place the steel.
11. Place the concrete around the steel carefully, ramming it so thoroughly that it will slush against the steel and adhere at every point.
12. Keep the forms rigid.
The fulfillment of these requirements will increase the cost of the structure; but if the recommendations are followed, there should be no difficulty in erecting concrete chimneys which will give thorough satisfaction and will endure.
Concrete Water Tower. The water tower illustrated in Plate 27 (at left) shows a new fea ture in reinforced concrete work, and another instance of concrete reinforced by steel taking the place of the all-steel structure.
The question is often asked: Can a success ful water tank be constructed of reinforced con crete? While this material has been used in the construction of both water and oil tanks for a number of years, and used successfully, the re markable work shown in the accompanying illus tration represents one of the greatest feats in this particular line ever accomplished.
The tower was built during the year 1907, at Ana heim, California. It will be noted that it is not merely a reinforced tank, but is a water tower in the strictest sense of the word. It is the first water tower in the world constructed entirely of reinforced concrete. Some idea of the magnitude of this work can be had from the following figures: From the lowest foundation to the extreme top, the tower is 112 feet, the tank proper being 30 feet in diameter and 38 feet in height, supported by concrete posts 60 feet above the ground. The tank has a capacity of 180,000 gallons, and is made throughout of concrete reinforced with rings and vertical members of twisted steel. The walls of the tank are but 3 inches thick at the top and 5 inches at the bottom. The floor is sup ported by concrete beams radiating from the center; and the twelve posts, each 16 inches square, are stiffened by two lines of horizontal struts, at equal intervals above the base. The structure is graceful in outline, and yet gives a pleasing appearance of massive solidity. The cost was $11,400, or about 75 per cent of the lowest estimate on a steel tank and tower of equal dimensions. About 800 barrels of Portland cement were used.