eS IF PO RPO Ne op ee At Ee} 
- DUST PREVENTION AND ROAD PRESERVATION, 1914. 39 
SUPPLEMENTARY REPORT OF EXPERIMENTS MADE AT KNOXVILLE, 
TENN., 1910. 
‘TAR AND OIL PREPARATIONS. 
The original report of these experiments was published in Circular 
No. 94, and reports of annual inspections are given in Circulars Nos. 
98 and 99, Office of Public Roads, and in U. S. Department of Agri- 
culture Bulletin No. 105. The sections were again inspected Novem- 
ber 18, 1914, and the following report was made: 
The weather had been dry for some time, and the temperature was 
slightly above freezing. No repairs have been made or maintenance 
work done during the past year. ; 
Section 1 (REFINED CoaL TAR—PENETRATION METHOD). 
This section is worn out, and the only places showing that tar was 
applied are those areas which were repaired a short time after the 
road was constructed. These patches stand out as islands about 2 
inches above the surface of the road. Along each edge of the original 
pavement is a border of the tar mat from 12 to 18 inches in width and 
of varying thickness, caused by bleeding of the tar. Between these 
borders the surface has worn down to the foundation course of stone 
except at the islands referred to. This course of stone is wearing 
unevenly, and save for a few places where the tar penetrated it is 
-water-bound macadam. It serves no further useful purpose as an 
experiment and should be rebuilt. 
Section No. 2 (REFINED TAR PREPARATION—PENETRATION METHOD). 
Between the south end of this section and a street intersection 340 
feet north, the surface is a succession of depressions and holes. About 
300 feet from the south end of the section the tar-treated wearing 
course is continuous across the pavement for a short length, affording 
the first opportunity of studying the cross section of the pavement as 
affected by wear only. From the street intersection northward for 
some distance the surface is in fairly good condition; and although it | 
is pitted with depressions of various sizes, there are few holes. In 
the last 100 feet there are quite a few holes, especially on the west 
side. This section should be reconstructed. 
Section No. 3 (O1r-AspHALT—PENETRATION MerHop). 
Except for a few depressions on the west side, the surface presents 
an excellent appearance. It has worn down to the wearing stone in 
places, resembling a bitumen-bound mosaic, but in no place has it 
lost its character as a bituminous surface, nor is there any evidence of 
raveling. Throughout the traveled portion the cross section is uni- 
formly well preserved. Such bitumen as was dug out with a knife 
