PRESERVING CEMENT SILO LINING. Ill 



Another objection to the silo is that poisonous gases are likely 

 to accumulate in the bottom and render the silo dangerous to en- 

 ter. Lowering a, light would soon discover the presence of such 

 carbon dioxide gas which if present would immediately put the 

 light out. These gases are heavier than air and the air would 

 have to be agitated to dispel them since there is no air drainage 

 in an underground silo. 



Again, unless the soil is dry and very hard or has excellent 

 drainage there would be the danger of water seeping into the 

 hole and thus spoiling the silage. The likelihood of caving in 

 either while building or after the first silage crop was taken out 

 would also have to be overcome. 



Some of the essentials in building underground silos aside 

 from firm dry soil are that they should have a curb or collar ex- 

 tending from below frost line to a, few inches above ground; that 

 they should be plastered from % to 2 or 3 inches thick and washed 

 with a cement coat to make them water- and air-tight, the walls, 

 being sprinkled lightly before plastering, if dry; that the walls 

 should be smooth and perpendicular for even, solid settling; that 

 a cover should be provided as a protection against children, ani- 

 mals or foreign matter and to insure free. air circulation. 



Preserving Cement Silo Lining. — The ordina'ty cement surface 

 is porous and as such not only absorbs water like a sponge, but 'a 

 open to the action of acids, alkali, etc. This porosity can be largely 

 overcome by either troweling the surface well before setting, or by 

 washing or painting with a coat of pure cement. 



Some damp-proofing paints are on the market, but care should 

 be taken to avoid the little bubbles that form which afterward 

 break leaving pin holes penetrating the coating. Several mami- 

 facturers now make a waterproofing material to mix with the con- 

 crete such as "Medusa," made by Sandusky Portland Cement 

 Co., Cleveland, and "Impervite," made by Standard Paint Co.. 

 Chicago. "Percoproof" is a black paint for waterproofing all kinds 

 of masonry, and is made by Philip Carey Co., Cincinnati. "Silo- 

 wash" is a combination of pure cement and "Impervite." Full 

 information should be secured from the manufacturers. 



