16 
BULLETIN 105, U. S. DEPARTMENT OF AGRICULTURE. 
bitumen showed a slight tendency to bleed. The necessary repairs 
were rapidly made by the patrolman, but as section markers had not 
then been placed, his costs could not be distributed. When the 
sections had once been put in thorough repair they were permitted to 
wear without further attention, with the results above given. 
The exposed concrete surfaces as a whole presented a smooth, 
uniform texture, and there was apparently no difference in wear 
between the plain cement and oil-cement concrete. The addition of 
hydrated lime has had no noticeable effect on the concrete. This 
section can not be distinguished from the others and has developed 
four cracks in a total length of 260 feet. Transverse cracks developed 
at varying intervals throughout the sections, and the average distance 
between cracks is shown in Table 18, which is based on observations 
made November 5, 1913. It should be noted that the cracks in the 
sections which had been surface-treated with bituminous materials 
include those which were noted before the surface treatment was 
applied as well as those which have since been noted through cracking 
of the bituminous surface. 
Table 18. — Average distance between cracks in concrete road of Chevy Chase, Md. 
Character of pavement. 
Length. 
Average 
distance 
Concrete. 
Aggregate. 
between 
cracks. 
Surface coated wi 
th bituminous materials: 
Gravel 
Feet- 
mO 
583 
230 
370 
425 
600 
300 
210 
260 
290 
Feet. 
45 
Do 
Limestone 
do 
145 
115 
Do 
Gravel 
50 
Surface exposed: 
do 
61 
Do 
Limestone 
Trap 
Limestone 
100 
Do 
40 
Oil-cement 
Do... 
105 
45 
Do 
Trap 
60 
It will be noted from the foregoing table that cracks have developed 
at a greater average distance where a limestone aggregate was used, 
and at the last inspection there were still two sections of the limestone 
concrete each 140 feet in length without a crack. When the edges of 
any cracks began to wear excessively, the cracks were filled with 
the water-gas tar preparation No. 1 and sand. The results of this 
treatment have thus far proved entirely satisfactory. 
The measurements referred to in Circular No. 99 are being con- 
tinued, and it is probable that interesting results will be reported in 
the near future. 
No difference was noted in the character of the various sections of 
brick pavement. The grouted surface had practically all worn off, 
and it was observed at a few places throughout the length of the sec- 
