DUST PREVENTION AND ROAD PRESERVATION, 1916. 55 
tion of the surface appeared imminent. It appeared probable that 
reconstruction of the macadam would be necessary. 
Section 4 was re-treated in October, 1916, and at the time of in- 
spection was in almost perfect condition. A few small spots near 
the north end showed excessive wear, but otherwise the surface was 
uniform and intact. The quantities and costs appear in Table 58, 
and the characteristics of the bitumen, which was the same as used 
im original construction, were the same as of that used on section 3. 
TABLE 58.— Materials and cost data for surface re-treatment, Washington, D. C., in 1916. 
Experi- F 
ment No. | Experi- |, DE No. 
Rome, 1, refined | ment No. 3 and ride 
ci water-gas | 2,asphaltic asph Aalto 
fer prep? petroleum. petroleum. 
ESO PERNEG Loanoosnose sosbeobe sac cs gece deoepsee ss + sagse acs sq. yds... 1,318 1,129 2,041 
Quantity of material per square vant 
Bituminous Material see oso os be oases sees seis 2/2 galls... 0.138 0. 152 0.113 
SBTC ocgscononsosoooodencoSeoascassodesscosssoSeer0s cu. yds... . 0064 - 0053 . 0046 
Cost per square yard (cents): 
Batimmnousimaterial’ so. ease ccssce asics ce see eee ss eae 1.38 1.70 1.81 
SPMG! sac seoesonssacnosngodososs soe osoescoss-cossebssoeosetese 1.03 - 86 2783 
Claritin? Ginnie ea ee BASS Se eean: BARNeeNeae eb Sa S ra eee MEH tai 05 06 13 
ieaaline ym atieniatsi. 5 sacs eee lc eie soe eae ete Jee ceciessn/sinis 1.08 27 88 
Applying bituminous materials.........------------------------ 42 56 56 
iNoyo) aele Bese | SEAS Seer see coc seh eee seus eae eee =Seeeeeseesesecoes = -41 49 17 
SOS AMNIGU 6 Go -cosees2eoces tod ocosesedoueasedeoscesosdoscasus -41 48 . 36 
PRO LAr eevee ciaitists sie slaie eles Lainishis sete dawns ceiesewicieecisieinelndine 4.78 4.42 4.64 
CHEVY CHASE, MD., 1912. 
BITUMINOUS CONCRETE, CEMENT CONCRETE, OIL CEMENT CONCRETE, VITRIFIED 
BRICK, BITUMINOUS SURFACE TREATMENTS ON CONCRETE. 
The original reports of these experiments were begun in Circular 
No. 99 of the Office of Public Roads and completed in Bulletin No. 
105, U. S. Department of Agriculture, and supplementary reports 
have been published in Bulletins Nos. 257 and 407, U. S. Department 
of Agriculture. The followmg report covers the condition of exper- 
iments on February 21, 1917. 
Experiment No. 1—Bituminous concrete, Topeka specification.— 
This section continued in essentially the same condition as at last 
report. At points 15, 25, and 30 feet from the north end of the lime- 
stone section three cracks appeared, extending about one-half of the 
width of the surface on the gutter side. About 70 feet from the 
north end of the trap section, near the gutter, there were two breaks 
with an area of about 1 square foot each. In one of these the con- 
crete base was exposed. The slight pitting noted in the last report 
had not increased. 
Expervment No. 2—Bituminous concrete, District of Columbia speci- 
fication.—This surface continued in the same condition as when last 
reported. Two cracks have appeared at 50 and 65 feet, respectively, 
