DUST PREVENTION AND EOAD PRESERVATION, 1914. 



9 



B. From stations, + 50 to 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 due 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 tarn. 



Lot No. 1. 



Lot No. 2. 



Specific gravity 25725° C 



Float test at 50° C. (time) 



Free carbon per cent 



Distillation: 



Water per cent 



Ughl oils to 110° C do.. 



Second light oils (110M70 C.) do. . 



: oil8(l70 , -270 a C.) do.. 



v oils (270 8 -815° <:.) do. . 



Pitch re Idue do.. 



1.288 

 4' 18" 

 29.61 



1.282 

 3' 33" 

 28.30 



By 

 volume. 



0.0 



i.l 



2 .6 



3 3.8 



4 11. 5 



«84. 



Total. 



100. 



By 



weight. 



By 

 volume. 



0.0 



.1 



.4 



3.0 



9.4 



87.1 



0.0 



2 .4 

 2.3 



«4.4 

 Ml. 4 

 «83. 5 



100. 



100.0 



By 

 weight. 



0.0 

 .2 

 .4 

 3.4 

 '9.0 

 86.8 



99. 



> One-half solid. 



2 Solid. 



3 C'londv. 



« One-eighth Bolid, 



One-fifth solid. 

 "Hard, dull, brittle. 



Method. — The rock course was rolled more heavily to reduce the 



voids below the percentage obtaining in experiment No. 1. The 



y refined tar 3 designated as lot No. l, was then applied at Mm*. 



rate of 0.98 gallon per square yard. The average temperature of the 



tar wa t75° C. The rock wa i dry and hot from the sun, the fear 



