Q.: One of our good farm customers is introducing anhydrous ammonia into his silage. (It is said that this increases its protein value.) Now he discovers that the walls and floor of the silo are deteriorating. Can this be prevented?

A.: The anhydrous ammonia reacts with silage acids to form compounds that erode hydrated portland cement by dissolving it. The eroded concrete surfaces should be chipped or scarified to remove all loose and unsound material, and thoroughly rinsed. The concrete walls and floor should then be brought to their original dimensions by applying a suitable portland cement plaster, or portland cement-latex plaster, using standard repair procedures that ensure good bond. Finally, the surface should be covered with an acid-resistant, abrasion-resistant coating or lining. An epoxy is the material most likely to meet these requirements. We suggest you ask one or more manufacturers for their recommendations about the kind of epoxy or other protective material, the thickness that is desirable, and whether they have any special system for building up a lining.

If the erosion of the walls and floor is only superficial so far, it may be possible to omit the plastering operation. The manufacturer of the coating or lining can undoubtedly advise about this.