EXPANSION" AND CONTRACTION OF CONCRETE. 
19 
initial contraction must be explained by the drying out of the mois- 
ture in the concrete. It has been shown in the previously described 
Fig. 15. — Curves of unit expansion and contraction of uncracked portions of concrete 
road, Chevy Chase, Md. 
laboratory tests that great shrinkage of concrete can take place during 
the initial stages of hardening, due to the drying out of the moisture, 
