MONOLITHIC CONCRETE SILOS. 63 



With this type it is convenient to use scaffolding of the 

 same plan as shown in the article on clay block silo con- 

 struction. There are several patented systems embodying 

 scaffold and forms. They are quite generally advertised and 

 may be learned of in that way. There are several systems not 

 patented. 



In some cases it will be found convenient to use thin sheet 

 metal for outer forms, but the inner forms must be either of 

 wood or quite heavy steel on account of the danger of collap- 

 sing. If, however, a rigid inner form is used, the outer 

 may be of light material and may be spaced accurately from 

 the inner form. This secures a properly shaped wall of uni- 

 form thickness. Any forms should be cleaned every time 

 they are used, and usually it is well to coat them with grease 

 or oil. This, however, leaves some grease upon the surface 

 of the concrete and interferes with plastering in case it is 

 desired. 



It is ordinarily advantageous to use two forms, the second 

 being put in place and filled before the first is removed. With 

 any system there should be separate forms for the door frame, 

 that is, it should never be necessary to use a wooden frame in 

 a concrete silo. After setting the forms they should be filled 

 around evenly about six inches at a time. Concrete should 

 not be dropped a great distance into them or any other rough 

 handling done with them, as it is not advisable to go to the 

 trouble of making forms that will stand much abuse. The 

 concrete should be thoroughly tamped or rammed with a 

 light rammer, and there should be sufficient water in the con- 

 crete to work to the surface by this process. The concrete 

 should be thoroughly spaded near the walls, in order to give 

 it a smooth and even surface. 



In putting steel into the concrete, place it at a reasonably 

 uniform distance apart and about half way between the inner 



