12 



BULLETIN" 532, U. S. DEPARTMENT OF AGRICULTURE. 



from the side of the S by S inch column. The curve on figure 11 was obtained 

 partly by measurement and partly by theory, assuming that the deformations 

 from the reinforced side to the plain side varied as the ordinates to a straight 

 line. This assumption has been shown to be true a number of times in the 

 cases of beams subjected to bending stresses. Note that the steel seems to have 

 bad a bending effect on the specimen, the unreinforced side shrinking much 

 more than the reinforced side. The amount of shrinkage on the plain side of 

 the column at the end of one year amounted to approximately 0.1 per cent ; that 

 of the steel amounted to 0.03 per cent. Any such shrinkage as this would tend 

 to cause compressive stresses in the concrete on the unreinforced side and ten- 

 sile stresses in the concrete on the reinforced side. In a concrete pavement, 

 with tbe reinforcement placed near the top or bottom, there would be unequal 

 shrinkage at these two surfaces, thereby creating a tendency to curl and crack. 

 To eliminate the unequal shrinkage in concrete pavements, due to eccentric 



£ ROUNDS 



.NOTE: CONCRETE OEFORMATIONS MEASURED ON UNREINFORCED S.IDE 



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Fig. 11. — Specimen reinforced on one side.' 



placing of t lie steel, and at the same time to take care of settlement cracks as 

 efficiently as possible, it is well to place the reinforcement in the center of the 

 pavement. 



MEASURING THE EXPANSION AND CONTRACTION OF CONCRETE 



ROADS. 



Although the laboratory measurements of expansion and contrac- 

 tion of concrete gave much information on the influences affecting the 

 length of a concrete road, the actual conditions of moisture in the 

 road are so different from those of the laboratory that it was thought 

 well to obtain additional information of the movements that take 

 place by actually measuring the changes in the road. 



A concrete road is subjected to a great range of variables. In the 

 initial stages of its hardening it generally is kept moistened arti- 



