DUST PREVENTION AND ROAD PRESERVATION. 



37 



tar preparation No. 2, 0.41 gallon per square yard. Sand was 

 spread over the flush coat at the rate of 0.016 cubic yard per square 

 yard. The joints in the paving brick patch were filled with sand. 

 Table 35 gives the analyses of the bituminous materials used. 



Table 35.- 



- Analyses of tar products used in surface treatment of oil-cement concrete at 

 Jamaica, N. Y. 



Materials. 



Refined coal tar. 



Water-gas tar prep- 

 aration No. 1. 



Water-gas tar prep- 

 aration No. 2. 



Specific gravity 25725° C. 

 Float test, 32° C. (time) .. 

 Float test, 50° C. (time) . 

 Per cent of free carbon . . . 



1.209 

 1' 3" 



1.172 

 16' 28" 

 2' 18" 

 1.35 



By 



volume. 



weight. 



By 



volume. 



Distillation: 

 Water 



First light oils to ii6°c! ! ! ! 

 Second light oils 110°-170° C 



Heavy oils 170°-270° C 



Heavy oils 270 °-315° C 



Pitch 



Total 



Per cent. 

 0.0 

 i .4 

 i .5 



3 17.9 



4 11.7 

 69.5 



100.0 



Per cent. 



0.0 



.3 



.3 



14.7 

 9.7 

 74.7 



Per cent. 

 0.0 



2.5 

 2.3 



2 2.3 



s 11.8 



85.1 



99.7 



100.0 



By 



weight. 



Per cent. 



0.0 



.4 



.2 



1.8 



10.1 



87.4 



99.9 



1.154 

 3' 20" 

 V 2" 

 1.45 



By By 



volume, weight. 



Per cent. 

 Trace. 



2 1.2 

 2.3 



2 5.4 



6 18.5 



74.6 



100.0 



Per cent. 

 Trace. 

 0.9 

 .2 

 4.0 

 16.2 

 78.5 



99. 



i Trace solid. 2 Clear. 3 One-third solid. 



5 Clear, showed 7.5 per cent insoluble in dimethyl sulphate. 



6 Clear, showed 2.5 per cent insoluble in dimethyl sulphate. 



4 One-sixth solid. 



When inspected in December, it was found that the part treated 

 with refined coal tar was in slightly better condition than that treated 

 with the water-gas tar preparation. Both sections showed similar 

 bare spots, about the size of one's hand, where the tar carpet had been 

 removed from the traveled way. The penetration patch in the center 

 of the roadway west of the wood blocks was a trifle low, and tended 

 to hold sand and dust, but the long patch just east of it on the south 

 side of the roadway was in good condition. 



Experiment No. 2. — Cut-back oil asphalt — Mixing method. 



In June this experiment was in very fair condition for a width of 

 about 12 feet through the center and for its entire width from station 

 4 + 50 to the east end of the section. The sides of the road from sta- 

 tion 1+98 to station 4 + 50 were rough, wavy, and badly worn, as 

 noted in circular No. 99. 



Repairs were made as follows: The entire surface of the section was 

 broken up with a scarifier from the west end to station 4 + 50. No 

 particular difficulty was experienced in the scarifying, and the bitu- 

 minous wearing course broke up into fairly small pieces. The bitu- 

 men seemed to have about the same consistency as when originally 

 put into the road. After the road was scarified, the bituminous wear- 

 ing course was further broken up with picks and shovels and spread 



