With regard to the roughness of the outside, metallic reinforcing
materials are divided into two classes, smooth and corrugated or
deformed. The general result of the many tests carried on in testing
laboratories seems to indicate that in strength of bond, if the
concrete is sufficiently rich and well mixed, smooth surfaces give
satisfactory results. Two kinds of reinforcement are much used—bars
and wire.
_Bars._—Round bars three-sixteenths or one-fourth of an inch in
diameter are the size and kind most used on the farm. The stock on hand
at blacksmith shops and hardware stores is generally from steel that
stretches too easily and therefore is not the best for reinforcement.
Companies which make a specialty of reinforcing materials can furnish
both rods and bars which stretch only under very large loads.
_Wire._—The development of the wire fence has produced a material well
suited for reinforcing purposes. Of equal size, such wire will produce
a stronger reinforcement than the material above described. In order
to obtain straight wire of the necessary length, the coils ordinarily
placed on the market should not be straightened out. Straight wire
can be obtained from dealers in the same manner as baling wire; that
is, either single or twisted into two or three-ply cables, and of the
length desired. The plain, ungalvanized fencing wire is the proper
kind, for galvanization adds nothing to the strength, and the metal
will not rust when incased in the concrete.