Cement for the Farm. 



419 



Plain and Beinforced — Concrete is either plain or reinforced. One 

 is concrete without any kind of reinforcement and in which all the 

 stresses are carried by the concrete. The other is plain concrete, re- 

 inforced with steel bars, beams or other forms of metal or material. 



Reinforcement is placed in concrete in order to take up certain 

 stresses and reduce the volume of concrete. Concrete is strong in 

 compression but weak in tension, so if steel is embedded in the con- 



Figure 8. Circular form. 



Figure 9. Circular form. 



Crete in the proper place to take up the tensile stresses, a great saving 

 of concrete is effected. The result is that reinforced concrete is the 

 cheapest where concrete material is costly and is adaptable for pur- 

 poses where plain concrete is unfitted. 



The reinforcement must be properly placed in order to develop 

 the strength of the structure. As for example, load a concrete beam 



