54 BULLETIN 586, U. S. DEPARTMENT OF AGRICULTURE. 
6 
When inspected on March 27, 1917, this surface showed a larger 
degree of failure than ever before. The first 175 feet from the west 
end has a line of “‘cup”’ holes, generally confined to the middle third 
of the roadway. The mat was smooth and almost perfect over the 
next 100 feet, and there were only two small breaks. Then followed 
another section about 40 feet long spotted with the characteristic 
“cup” holes. The mat close to the “cup” holes was unbroken and 
although many of the holes were not over 3 or 4 inches in diameter 
and probably 90 per cent not over 8 inches across, many were an 
inch deep and some as much as 14 inches. Along the last 200 
feet at the east end of the section, seepage from the bank had done 
more damage than in any previous year. The “cup” holes con- 
tinued along this part of the road, with an almost intact mat between 
them. This experiment showed the need of considerable repair 
and a general re-treatment in the summer. 
Sections 3 and 4—Asphaltic petroleum.—Section 3 was repaired 
thoroughly in the summer of 1916 and given a re-treatment at the 
same time as Section 4, and the same materials were used, so that the 
two sections are alike. Owing to the variation in past history, how- 
ever, the three sections, 2, 3, and 4, will be continued separately so 
far as necessary. The re-treatment costs for section 3 appear in 
Table 58 and the analysis of the bituminous material is given in 
Table 57. - 
TaBLE 57.—Analysis of asphaltic petroleums used in re-treatment of experiments Nos. 
. 2, 8, and 4, Washington, D. C. 
Experi- Experi- 
Inent ments Nos. 
No. 1. 3 and 4. 
Soeeiie eA liny HPAP Coossnssoscoscqssoobcaesoosdsodoas seoKa shades doaSonAseace 0.950 0.956 
Flash point (°'C.).-------- 2-22 - +2. 2622-2222 2222 nee ee eee eee 18 28 
Isiopeabiaye ofeyba} 9 (CCB) So55- ess aos ses ccssae sos see saees cee ase seceossoseqeusseecaus 27 50 
Specific viscosity, Engler 25° C., 50 c. c..-.---.---------.------------------------ 108.6 187.5 
oss at 1635 C.,)o) OUTS, 2OeTaIM See es ee eee saree sec ee eee per cent 22.45 28. 23 
Float test on residue, 50° C. seconds...-....-------.----------.------------------ 119 
Per cent of total bitumen insoluble in 86° B. naphtha.........-.-.-.-.-.-.-.-.-- 8.08 16.58 
IDbG6l COO. 5 oo s5o5dac coos dodsgossactd4so0s sce gsocagdeonsoosonedse per cent 5.49 9.04 
Bitumen soluble in CS» (total bitumen) .........-.-.-..----.-.-------- per cent. 99. 95 99. 95 
Organieimatteminsolublesse-cees-ceee eee eee eeee cee eee eee ee per cent. . 05 .05 
Imorganicanaterinsolublepee. -eeeria ce cee aaa ee cece testes seek per cent. - 00 00 
WMO 55 Ghossasasecpedes seoud sepa sccasaccpe ges 2005c0Ns=sac0e03¢ per cent... 100. 00 100. 00 
The mat on section 3 in March, 1917, was failing quite generally over 
all but 150 feet, where the drainage was best. Raveling of the mac- 
adam had started in a number of places and the effects of poor drain- 
age, especially for the westerly 250 feet where the roadway is in cut, 
was more evident than at any time since construction. The south 
side had softened and rutted and many of the broken areas in the sur- 
face had spread until they had run together and a general disintegra- 
