TC-3. TAR FOR COLD PATCHING. 
General. 
The tar shall be homogeneous. 
It shall meet the following requirements: Physical and 
1. Specific gravity 25°/25° C. (77°/77° F.) 1.100 to 1.200 eS!" 1 Pr ° P " 
2. Specific viscosity at 40° C. (104° F.) 40 to 70 
3. Total distillate by weight : 
To 170° C. (338° F.) not less than 2.0 per cent 
To 270° C. (518° F.) 15 to 25 per cent 
To 300° C. (572° F.) not more than 30.0 per cent 
4. Total bitumen (soluble in carbon disulphide), 
not less than 80% 
Tests of the physical and chemical properties of the tar shall be Methods of test- 
inc. 
made in accordance with the following methods : 
1. Specific gravity, Department of Agriculture Bulletin 314, 
p. 4. 
2. Specific viscosity (on first 50 c. c), U. S. Department of 
Agriculture Bulletin 314, p. 7. 
3. Distillation test, A. S. T. M. Standard Test D 20-16. 
4. Total bitumen, U. S. Department of Agriculture Bulletin 
314, p. 25. 
This specification provides for a material to be used in the re- 
pair of surface breaks, holes and depressions in bituminous-bound 
and surface-treated roads. It is intended to cover preparations 
consisting of gas-house, coke-oven, or water-gas tars or pitches 
which have been rendered sufficiently fluid by the addition of 
distillates to enable them to be handled without heating. 
For surface breaks and shallow depressions or those which in 
general do not exceed one-half inch in depth, a patch may be 
made by painting the bottom of the depression with the tar, and 
scattering over it a sufficient amount of stone chips to fill the 
depression. 
In repairing deeper depressions and holes, the old material 
should be removed to yield a clean bottom. The sides of the hole 
should be cut approximately vertical. A mixture of graded broken 
stone with just a sufficient amount of tar to thoroughly coat each 
particle should be prepared, and firmly tamped into the hole to 
form a neat patch in the surface. A thin layer of sand or screen- 
ings over the patch will prevent it from picking up under traffic. 
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