20 
BULLETIN 1077, TJ. S. DEPARTMENT OF AGRICULTURE. 
JOINTS. 
Concrete contracts or expands with changes in temperature and 
differences in moisture content. It also shrinks materially during the 
period of setting and initial drying out. In practically all early 
concrete pavements transverse expansion joints were constructed 25 
to 30 feet apart, with the idea of relieving the pavement slabs of all 
stresses due to expansion and contraction, thereby preventing trans- 
verse cracking due to tensile stresses or failures due to compressive 
., T^ PTC. 
Normal w 
Width i vv 
La , 
RTt 1 
dclj = Coordinates of Point opposite PC. 
dc, u, = Coordinates of PC, 
F= Offset from Tangent to Circular Curve. 
£,,= Length of Transition Curve. 
I°= Central Angle of Transition Curve, 
= Central Angle of Circular Curve from PC. 
vj= Amount of Pavement Widening. 
Fig. 5. — Method of widening curves using transition curves. 
stresses. In these pavements it was found, however, that a majority 
of the slabs cracked transversely, that it was very difficult to secure 
a pavement with good riding qualities in the neighborhood of the 
joints, and that if the expansion joints were not constructed so as to 
be perpendicular to the surface of the pavement the end of one slab 
was very likely to rise above the end of the adjacent slab. Not in- 
frequently this relative movement amounted to 2 or 3 inches and in- 
convenienced traffic very materially. If the joint varied from the 
