DUST PREVENTION AND ROAD PRESERVATION, 1914. 9 
B. From stations,0+50to 1+ 02, approaching rains necessitated the 
sanding of the seal coat immediately after application. This caused 
a marked difference in the resulting surface condition of portions A 
and B of the experiment. The mat on the latter contained an 
excess of bitumen, and more sand had to be added from time to time 
until a thick, mushy top was formed. About a month after con- 
struction this mat was removed, heated, and respread to a thickness 
of about one-quarter of an inch. 
The bituminous material used in this experiment was found to 
contain a small percentage of water, probably duc to seepage through 
the barrels during transit. In heating, when the temperature reached 
the boiling point of water, the material foamed so excessively as to 
cause overflowing from the kettles. It was necessary, therefore, to 
apply the oil at a temperature of about 95° C., which was lower than 
desirable for best results and caused the rate of application to be 
greater than necessary. It was also found that the top voids, although 
assisting in securing excellent penetration, were too large to assure 
good results when filled with sand dressing. 
EXPERIMENT No. 2 (REFINED CoaL TARS—PENETRATION METHOD). 
Location: Station 1+02 to station 1+94=92 feet. 
Area: 153.3 square yards, 
TABLE 5.—Analyses of refined coal tars. 
' Lot No. 1. Lot No. 2. 
Spe ciieioranntyezon)| Zoe Cran mciecinclscamosleines ce scialee cee = alee nes 1. 288 1. 282 
Float test at 50° C, (time) 3/ 33!" 
TCE CAL OMe eaters eee eae ae Se tee ne ee cent. - i 28. 30 
y 3y By By 
volume. | weight. | volume. | weight. 
Distillation: 
fare Tyee eer ah eatin era arya cio ae Metra stare a ciniets per eon 0.9 0.0 0.0 0.0 
Mirshliohtroustot1OKCen 6 ee) oe ee eee do... 1,1 cl 2.4 .2 
Second light oils (110°-170° (8) ease sete Pa rp dons. 2.6 4 2.3 4 
ATCavsyeOUs Ai 0c—2 (OC eye Caan e eae le ied) aoe do..-- 33.8 3.0 34,4 3.4 
Lea OMS AROS 31D | C2) cing a nein sipistaiein sie inido sia vine MOneee 411.5 9. 4 511.4 9.0 
PAE CIFESTO UC cyoct fone cM crcte eeatele re ha ee LG smn oN doz2*: 6 84.0 87.1 6 83.5 86.8 
PT OG RL ae aera tnic ches raya care Wt ctate Mansi eee Mn NLR AN OO 8 I MSS 100. 0 100. 0 100. 0 99.8 
1 One-half solid. 3 Cloudy 5 One-fifth solid. 
2 Solid 4 Oreo one solid. 6 Hard, dull, brittle. 
Method.—The rock course was rolled more heavily to reduce the 
voids below the percentage obtaining in experiment No. 1. The 
heavy refined tar, designated as lot No. 1, was then applied at the 
rate of 0.98 gallon per square yard. The average temperature of the 
tar was 175° C. The rock was dry and hot from the sun, the tar 
