SILOS AND SILAGE. 



23 



6 inches at each raising. For raising the forms and hoisting the concrete, block 

 and tackle is necessary. When the forms are removed each time smooth down 

 both surfaces with a board, and when the silo is completed go over the inner surface 

 with a thin coat made of 1 part cement to 1 part sand, applying it with a whitewash- 

 brush. Keep the inner surface wet for a week, and a smooth and lasting surface 

 will result. 



REINFORCEMENT. 



Different shapes of iron and steel are used in reinforced-concrete construction. 

 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 ; %-inch steel rods may be used, but are more suitable for vertical reinforce- 

 ment. 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. 17.) To prevent a concrete silo 

 from becoming porous they should be painted on the inside every couple of years 

 with a thin solution of cement and water. 



DOORS. 



The continuous doors are just as advantageous in the case of the concrete silo 

 as the stave silos. The reinforcement, however, must be continuous and extend 

 clear around the silo or the construction might spread at its weakest point. This 

 weakness is overcome in this plan by the use of two 2-inch gas-pipes as shown in 

 Fig. 16. Holes large enough to receive %-inch rods are drilled in both pipes in the 

 same relative positions at intervals of 12 inches. Through these holes %-inch stay- 

 rods are placed as shown in Fig. 16. These stay-rods also form a convenient ladder 

 for gaining access to the. silo. 



