LIME, CEMENT, AND CONCRETE 



259 



210. Modulus of elasticity of concrete. Concrete is so imperfectly 

 elastic that the modulus of elasticity varies with the stress. It also 

 changes with the age of the material and with the change in propor- 

 tions of cement, sand, and stone. 



The variation in the modulus of elasticity with the stress makes 

 it difficult to make theoretical computations in which the modulus 

 of elasticity is involved, as, for instance, in such problems as arise 

 in connection with reenforced concrete beams, etc.* 



MODULUS OF ELASTICITY OF CONCRETE IN COMPRESSION 



For the method of computing the modulus of elasticity for materials which do not 

 conform to HM>k-'s l;iw see Article 65. 



