CEMENT BLOCK SILOS. 



97 



crushed stone is more commonly used. This is one of the 

 reasons why the monolithic wall is stronger than the block wall. 



Good block silos can be put up with home-made blocks and 

 by home labor, but an experienced contractor is recommended, 

 if convenient. No blocks that are cracked, broken or crumbly, 

 should be used, and all blocks should have good water-resisting 

 qualities. A small amount of water placed on the surface, if 

 readily absorbed, indicates a poor block for silo purposes. 



The Iowa Bulletin No. 141 says that "the practice of using 

 wooden studs for the door frame in mortar at the ends of the 

 blocks and at each side of the doorway and bolted to the steel 

 frame cannot be criticised too severely. This stud is placed 

 under conditions best adapted to cause rapid decay. Often it 

 is so constructed that it cannot be replaced without much diffi- 

 culty and thus the durability of the entire structure is impaired 

 by the use of a single part." Fig. 39 illustrates a poured con- 

 crete door frame that avoids this difficulty. 



Fig. 39. — Continuous door opening for concrete block silo. 

 View shows the manner of fastening reinforcing rods 

 to the door frames, also of anchoring rods around a block 

 instead of lapping. 

 — Courtesy Universal Portland Cement Co., Chicago. 



