16 BULLETIN 532, U. S. DEPARTMENT OF AGRICULTURE. 
Section III. Cement concrete, surface treated with bituminous materials. 
Section IY. Oil-cement concrete. 
Section Y. Cement concrete. 
Section YI. Yitrified brick. 
Some of the above sections were not built in continuous lengths. 
Because of unfavorable weather, work was stopped on this road 
on December 15, after the concrete of Section III had been poured. 
Work was resumed in the following spring and carried to comple- 
tion. On the bottom of figure 13 will be found a partial layout of 
the various sections of the road as constructed, giving the elates of 
construction and the character of the coarse aggregate. A complete 
description of the road and method of construction may be found in 
other publications of this office. 1 
During the construction of the cement concrete sections bronze 
plugs of the type previously described were inserted in the road sur- 
face, spaced 10 feet apart in a line 5 feet from the east sid; f the 
road. At every fifth plug there was placed also a trans- . . plug 
offset 10 feet from the line of plugs paralleling the road. ue layout 
of the sections of the road measured is shown in figure 13. 
The first set of measurements was taken as soon as practicable 
after the concrete had hardened. The dates and temperatures are 
given on this plate just above the road layout. Referring to the 
second set of readings, it will be seen that in general, when the tem- 
perature is lower than the initial temperature, the uncracked portions 
of concrete show contraction, and when the temperature is higher 
than the initial temperature, expansion occurs. Cracks are indicated 
by dotted lines and are seen at various intervals throughout the 
length of the road, in practically all the different sections except 
that containing limestone aggregate. In the cold weather, during 
which this set of readings was taken, the cracks opened up, as shown 
by the expansion readings. The shrinkage of the concrete naturally 
would cause an opening of the cracks. 
In the spring of 1913 a bituminous carpet coat was placed over 
the concrete up to the end of the oil-cement gravel- aggregate section 
(station Xo. 210), and expansion measurements were made in the 
hot weather of the spring, summer, and fall. It is interesting to 
note that the readings taken on July 3, 1913, all showed expansion, 
even those taken over the cracks. Expansion at the cracks as well 
as in the concrete is rather difficult to account for with certainty. 
However, during the previous winter the cracks undoubtedly opened 
up very wide during the coldest weather, owing to low tempera- 
ture contraction, aided perhaps by the freezing of water in the cracks, 
and became filled with material from the road which prevented 
. i Office of Public Roads Circular No. 99. U. S. Department of Agriculture Bulletin 
No. 105. 
