DUST PREVENTION AND ROAD PRESERVATION, 1914. 39 



SUPPLEMENTARY REPORT OF EXPERIMENTS MADE AT ENOXVILLE, 



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 cpuite a few holes, especially on the west 

 ride. This section should be reconstructed. 



No. 3 (OlIrAsi'M.M.T I'kn'ktration Method). 



Except for a few depre ions on the west side, the surface presents 

 an excellent appearance. It bias worn down to the, wearing stono in 

 cabling a bitumen-bound mosaic, but in no place lias it 

 I' i- 1 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 



