CHAPTER XIV 



REENFORCED CONCRETE 



213. Object of reenf or cement. The fact that concrete is much 

 stronger in compression than in tension has led to attempts to 

 increase its tensile strength by imbedding steel or iron rods in the 

 material. This metal reinforcement is so designed as to carry most of 

 the tensile stress, and thus plays the same part in a concrete structure 

 as the tension members play in a truss. 



It has been found by experiment that reenforced concrete beams 

 may be stressed in flexure far beyond the elastic limit* of ordinary 

 concrete, and even beyond the stress which would rupture the same 

 beam, if not reenforced, without appreciable injury to the material. 

 M. Considere, one of the leading French authorities on the subject, 

 reports a test of this kind, in which he found that concrete taken 

 from the tensile side of a reenforced concrete beam tested in flexure 

 was uninjured by the strain. Professor Turneaure, of the University 

 of Wisconsin, has found that minute cracks occur on the tension side 

 of a reenforced concrete beam as soon as the fiber stress reaches the 

 point at which non-reenforced concrete would crack, f Experiments 

 of this kind seem to indicate that the metal reenforcement carries 

 practically all of the tensile stress, as cracks in the concrete must 

 certainly reduce its tensile strength to zero at this point. 



214. Corrosion of the metal reenforcement. The maintenance of 

 the increased strength of concrete due to the metal reenforcement 

 depends upon the preservation of the metal. The corrosion of metal 

 imbedded in concrete is thus a matter of the greatest importance in 

 connection with reenforced concrete work. It has been found that 

 metal thus protected does not corrode even though the concrete be 



* As indicated in Chapter XIII, concrete shows no well-defined elastic limit, i.e. the 

 material does not conform to Hooke's law. In this case elastic limit means the arbitrary 

 point beyond which the deformations are much more noticeable than formerly. 



t Proc. Amer. Soc.for Testing Materials, 1905. 



263 



