64 SILOS: CONSTRUCTION AND SERVICE ' 



and the outer forms, but in no case put any reinforcing 

 material closer than 1 inch from the surface of the concrete, 

 also avoid any reverse curves in the steel. Where two pieces 

 of reinforcing steel join they should lap at least 2 feet, to pre- 

 vent slipping. Usually, good concrete need only to set over 

 night, when the form may be removed and raised. 



One advantage of using two sets of forms is that in no case 

 is it necessary to remove them until 18 hours after they have 

 been filled. The common depth of a set of forms is 2J^ to 3J/ 

 feet, but by using two sets, 5 or 6 feet can be added to the 

 silo each day. 



Vertical reinforcement should be used on each side of the 

 doorway. In any silo more steel should extend across the 

 doorways than is found in other parts of the wall. Wall 

 reinforcement ending at the doorway should be hooked to the 

 vertical reinforcement. 



Plastering. In case it is necessary to plaster this silo it 

 is most conveniently accomplished on the outside from a 

 swinging scaffold either suspended from the forms, or, if the 

 silo is completed, the scaffold may be supported from the 

 cornice. On the inside, it is usually most convenient to 

 remove the forms and plaster from the scaffold as it is low- 

 ered. It is better, however, to plaster the silo if possible 

 before it has thoroughly dried, as there is not much danger 

 then of the plaster drying too rapidly. 



Methods of hoisting material will vary with different 

 systems of forms, etc. In most outfits on the market a con- 

 venient method of hoisting is provided. If, however, other 

 means are not available, a gin-pole, shown in connection with 

 block silos, Fig 22, will be found very convenient and 

 strong enough to hoist at least 100-pound loads. 



