26 



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



sions at some of the expansion joints, and the joint which had pushed 

 together and overrode during the preceding summer remained in the 

 same condition. 



In an effort to determine whether atmospheric moisture or tem- 

 perature played the most important part in influencing the expansion 



9 5 

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Fio 19. — Curves of unit of expansion and contraction of uncracked portions 

 of concrete road, Oliio I'ost Road. 



and contraction of the Ohio road, the curves shown in figure 19 

 were plotted. The unit expansions and contractions shown were 

 obtained by summing up the changes in the concrete in the uncracked 

 portions. Each curve represents the unit deformation in a different 

 slab of concrete included between different joints or cracks. In the 

 same section of road these curves should be of practically the same 



