Thermal conductivity and surface treatment of silo walls
1. Temperatures taken inside the north wall on concrete, hollow block and wooden stave silos, follow outdoor temperatures rather closely and show little advantage in favor of any one material.
2. Temperatures taken near the center of the silo are higher than and fluctuate less than those near the wall surface.
3. Under most conditions, silage itself is a good insulator. Much heat may be lost through open doors, of out of the top of an unroofed silo. Exposure to cold winds is an important factor. Any of these or a combination of them may have more influence upon the amount of frozen silage than the construction of the wall.
4. All of the materials tested in connection with the study of wall surface treatments gave complete protection for a limited time only.
5. Cement plaster gave the best protection in rendering a clay block silo wall air-tight, but considerable difficulty was experienced in securing a satisfactory bond with the tile.
6. Bituminous coatings have proved satisfactory on tile silos and are easily applied. A high grade roofing cement containing asbestos fibers in asphalt, will stay in place better than asphalt alone. At least the first coat of this cement should be thinned with gasoline to a consistency which will permit application with a brush and so that it may be used cold. Hot applications of asphalt chill quickly upon contact with the cold silo wall, harden at once and fail to bond.
7. The apparent necessity for wall treatment on concrete stave silos has been to stop, or at least retard, the corrosive action of silage acids. Several of the materials accomplished this purpose fairly well. Difficulty was experienced with all specimens due to the scaling of the original cement wash. For this reason, if the wall has been coated with a cement wash, treatment should be deferred until all traces of the original wash are gone. It may appear necessary to act at once to preserve the interior surface of the silo. This corrosive action, however, is not as serious as it may seem at first, and the results will well repay one for waiting. Any treatment applied following a cement wash is likely to fail because of imperfect bond between the wash and the stave.