REINFORCING CONCRETE; CEMENT TOOLS 137 



placed where it will be under a tensile strain. Fig. 144 shows 

 the relative strength of a concrete beam with reinforcing 

 placed in various positions. 



136. Kinds of Reinforcing. As to the kinds of rein- 

 forcing, probably square twisted steel rods, or the deformed 

 bars, are best. Round rods are sometimes used, but they 

 should be carefully anchored to give the best results. Some 

 engineers specify either the twisted or the deformed rods, 

 since a better bond is secured between the concrete and the 

 steel with this type of reinforcing. Some contractors claim 

 that a small amount of rust on the reinforcing is advanta- 

 geous. A very small amount of rust may be of some value in 

 forming a bond between the concrete and the steel. How- 

 ever, if the steel is left outside until it has become pitted with 

 rust, the resultant piece of work would be weakened, as the 

 bond between the steel and concrete would be a poor one. 



137. Use of Scrap Iron for Reinforcing Concrete. It 

 is thought by some that scrap iron will make good reinforcing. 

 It is seldom true that as good a job can be secured by using 

 scrap iron, old gas pipe, etc., as by using regular reinforcing 

 steel. Gas pipe that is of value as pipe is expensive rein- 

 forcing material. 



138. Tools for Concrete Work. Very inexpensive tools 

 are required for concrete work; in fact, few tools that are not 

 found on the average farm. For special work, special tools 

 will be required, which may be secured from any good hard- 

 ware supply house. A panel containing many of such special 

 tools is shown in Fig. 145. The tools commonly used in farm 

 concrete work and such as will be needed in the following pro- 

 jects .are as follows: 



