13 



REINFORCEMENT. 



Different shapes of iron and steel are used in reinforced-coucrete construc- 

 tion. For silo-construction wire is very satisfactory, as it offers a rough 

 surface where wires are twisted together to form a cable, and laid as a 

 continuous band in the concrete. Three-eighths of an inch steel rods may be 

 used, but are more suitable for vertical reinforcement. Wire, to be fit for this 

 purpose, should approach % inch in diameter, and be of good material and 

 not old. 



Pour about 1 foot of concrete into the forms all the way round, then lay 

 in the reinforcement about 2 inches from the outside of the wall. The size 

 of the cable needed can be determined by the table given below. If rods are 

 used, the ends must be firmly hooked together. 



AMOUNT OF HORIZONTAL REINFORCEMENT NEEDED FOR SILOS. 



Silos 25 feet high, and 10 or fewer feet in diameter, are stated to need 

 no vertical reinforcement except around the door openings. It is, however, 

 a safe plan to place rods, iron or steel, 3 feet apart vertically around the silo. 

 Short lengths, 3 or 4 feet long, with the ends bent into hooks to join them, 

 are found convenient. On either side of the doors vertical reinforcement must 

 be placed and joined by twisting with the horizontal reinforcement. 



(Fig. 6.) Reinforcement around doors. 

 DOORS. 



To construct a door-form, make a frame of 2- by 4-inch lumber, 2 feet 

 wide by 2 feet 6 inches high. Then take pieces of 1-inch by G-inch lumber, and 



