26 - BULLETIN 257, U. S. DEPARTMENT OF AGRICULTURE: 
EXPERIMENT No. 1 (BiruMINous CONCRETE—TOPEKA SPECIFICATION). 
This experiment presents a hard firm surface, with some slight 
indication of waviness. The latter condition is most pronounced in 
the trap-rock section adjacent to the curb. The wear in this pave- 
ment is most evident where the surface is slightly below the top of 
the concrete curb, and in one place this has been broken and a slight 
depression has developed. The trap-rock section has a slightly 
darker color than that in which limestone was used, and the line 
between the two is easily discernible. Two lateral cracks were 
noted in the limestone section about 20 and 40 feet, respectively, 
south of its juncture with the trap-rock section. These cracks 
extend from the west curb about half way across the road. A 
small cup-hole was noted in the middle of the road about 60 feet 
north of Bradley Lane. 
EXPERIMENT No, 2 (BrrumiNous CoNCRETE—DIstRIcT oF CoLUMBIA SPECIFICATION). 
This experiment presents a smooth uniform surface on which the ~ 
seal coat still remains practically intact. Two lateral cracks, both 
beginning at the east curb, were noted near the middle of the section 
in which trap rock was used. One of these extends about one- 
quarter of the distance across the road and the other about one-half 
the distance. 
During the early summer of 1914 expansion in the concrete again 
caused a buckling of the surface at the jomt between experiments 
Nos. 2 and 3. The stress developed was sufficient to force out the 
bricks which had been used in providing for this condition previously. 
The bricks were therefore removed, a clean trench was cut out en- 
tirely across the pavement for a width of about 1 foot and filled with 
Portland cement concrete. ; 
EXPERIMENT No. 3 (CEMENT CONCRETE AND O1IL-CEMENT CONCRETE—SURFACES 
TREATED WITH BITUMINOUS MATERIALS). 
The several sections of this experiment have been permitted to 
wear without repairs, and the condition of the various sections at the 
time of this inspection was noted as follows: 
(A) Refined coal tar.—The surface treatment has worn off in fairly 
large areas throughout the entire section. 
(B) Water-gas tar preparation No. 2.—The surface has worn off in 
small areas throughout the entire section, in most cases not exceeding 
1 square foot. This section is in an appreciably better condition — 
than No. 1 through its retention of more of the original treatment. 
(C) Fluaed native asphalt No. 2.—The bitumen in this section is 
still quite pliable, but the surface treatment has largely worn off over 
