208 FAKM BUILDINGS IN SOUTH AFKICA 



Thus the silo illustrated will hold 5880 x 39'6 = 232,848 lbs. = 116 

 short tons fully. 



Having settled the size of the silo to be erected, the next thing which 

 occupies our attention is the construction. 



Materials of Construction. — The materials of construction most likely 

 to come into extensive use in this country are stone, brick, and reinforced 

 concrete. In parts of America where wood is plentiful, wood stave silos 

 are used. These silos are circular, and are constructed of wooden staves 

 set on a stone foundation and held together by iron hoops. The wood 

 stave silo is open to many grave objections, most of which would probably 

 be aggravated by the climate of this country. 



All-metal silos are also manufactured, but seem open to the objection 

 that the plates composing them are subject to the corrosive action of 

 the silage juices. 



The silo illustrated may be constructed of either stone or brick. 



Part below Ground. — This (in the design illustrated) should preferably 

 be built in cement mortar, and is best made of stonework, even though 

 the remainder of the walls above ground are of brick. In place of 

 using pure cement mortar, a cheaper mortar may be employed consisting 

 of one part cement to four parts lime to fifteen parts clean sand. 

 In the latter case, if the site is damp, the whole of the outer surface 

 of that part below ground had better be coated with a damp-proof 

 composition, consisting of one part tar, two parts pitch, and four resin, 

 applied hot. The walls of the bottom portion of the silo are 27 inches 

 thick, and are carried at least one foot above the ground in the case of 

 the upper walls being of brick. 



The silo should not be filled for at least two months after completion, 

 in order to give the mortar in the walls time to strengthen. 



Great care should be taken in building the lower part of the silo, 

 and also the parts surrounding the emptying doors, especially the lower 

 ones, as the walls are subjected to the greatest pressure at the base. 



The excavation in the earth to receive the lower part of the silo should 

 be made large enough to allow of thorough tamping of the earth-filling, 

 so that it may act as a strong backing to the wall. 



The Walls above Ground. — If of stone, these may be 24 inches thick 

 at the bottom, tapering to 16 inches at the top. If of brick, the walls 

 may be 2£ bricks or 22 inches thick at the bottom, and 1£ bricks or 

 14 inches at the top. They should be built in English bond, the bricks 



