32 BULLETIN 257, U. S. DEPARTMENT OF AGRICULTURE. 
At the time of inspection the section generally presented a firm: 
smooth surface. A few small cup-holes had formed where repairs 
were made before the last surface treatment, and were undoubtedly 
due to a poor distribution of oil asphalt in placing the patches. 
Section No. 10 (REstpuAL PETROLEUM—SuURFACE TREATMENT). 
The development of irregular humps and ruts upon this section, 
noted in U. S. Department of Agriculture Bulletin No. 105, con- 
tinued during the past year, until the surface was in such condition 
that it was deemed advisable to remove the surface mat as far as 
possible and re-treat the entire section. Accordingly the surface mat 
was broken up by means of a 3-ton scarifier, and as much of it re- 
moved as could be easily separated from the macadam stone. The 
old surface was then loosened by scarifying and picking, shaped with 
rakes, and brought to grade by the addition of a thin course of ?-inch 
limestone. After rolling, limestone screenings were scattered over the 
surface just sufficient in quantity to fill the surface voids. The sur- 
face was then thoroughly bonded by sprinkling with water and rolling. 
The following table gives the materials and cost data per square 
yard for the reconstruction of the water-bound macadam surface. 
TABLE 23.— Materials and cost data for reconstruction of section No. 10, Chevy Chase, Md. 
Materials used per square yard: 
Lp oral linmestome ua. seer st ee cae ey Lge eens Mean en cubic yard.. 0.001 
G-Tech MIMes OMe <a" ean hoc eke a ee oe See eee ee dG 52 086 
‘Limestone screenimosnis te tee Oo es es a ee dove Ea 008 
Cost per square yard: 
fonchilinestomels Meco ceil saan ce peee Ge eee ee cenisaca- ane 
2-ineh limestome sce 2 ees Se a See et do.... 4.060 
NIMeSLONe SETERMINES 25 Os Goes a see ee ee eee a ge do. 2s e8tsZe 
Sweepine old suriaces: c.f ce see ec ae ere ee eee oe ee Ere doe to a 
Removing old suriace mat. -22 St San. Sie i eet eee dei Esser 
Scariiying, and rakine scarified Surface. .:-2.286-------- 2. 2 Joe SO eee 
Spreadimesstome 224 oo eee ee epee eee te ec ee dom: = eso 
ho] OVNGH '¢ Ntc1 gaint ee ENE SEM tn i Toman ae cc aay ere ee doses abt 
O20) Us Yale Mele ag nie i ears Cen SN ol ee uae ee do. 25°92. 898 
{Cl i ear eM SRC. Oy ey go he ss dos 33, Aiy620 
On November 3 and 4, after several days’ traffic over the water- 
bound surface, the section was given a cold surface treatment with 
an asphaltic petroleum of the analysis given in Table 22. This was 
covered with washed 3-inch gravel. The bituminous material was 
applied by allowing it to run from the bungs of the barrels directly 
upon the road, which had previously been swept with hand brooms 
to remove loose material. The oil was broomed over the surface 
until no uncoated spots remained, and it was found that considerable 
-brooming was necessary, owing to the fairly large amount of dust 
