ing 
TC-2. TAR FOR COLD APPLICATION. 
General. The tar shall be homogeneous. 
Physical and It shall meet the following requirements: 
chemical prop- L Specific gravity 25°/25° C. (77°/77° F.) __1.100 to 1.140 
2. Specific viscosity at 40° C. (104° F.) 25 to 35 
3. Total distillate by weight: 
To 170° C. (338° F.) not more than 2.0 per cent 
To 270° C. (518° F.) not more than 25.0 per cent 
To 300° C. (572° F.) not more than 35.0 per cent 
Methods of test- 4. Total bitumen (soluble in carbon disulphide) 95vr tol00% 
Tests of the physical and chemical properties of the tar shall 
be 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 primarily for a material to be used 
in the surface treatment of macadam, gravel, or shell roads to 
form a thin wearing mat or carpet which may be built up by sub- 
sequent maintenance treatment of either the same type of mate- 
rial or a heavier product (Specification TH-1). It may also be 
used for maintenance of tar macadam or tar concrete roads, for 
which purpose it is considered preferable to specification TC-1. 
The specification is intended to cover water-gas tar and low car- 
bon coke-oven tar products. 
A successful treatment requires that the road surface shall be 
in a good state of repair, well consolidated, free from holes or 
depressions, and thoroughly swept for the removal of dust and 
detritus before the application is made. Newly constructed or 
reconstructed roads should be permitted to consolidate under 
traffic before the tar is applied. The tar may usually be applied 
without heating excepting when cold weather renders it too vis- 
cous to distribute properly. The initial application should be 
made by means of a pressure distributor at the rate of from one- 
third to one-half gallon per square yard. It should be covered 
with a uniform layer of dustless broken stone all of which will 
pass a one-half or three-quarter inch laboratory screen or pea 
gravel, which will pass a one-half inch laboratory screen in an 
amount just sufficient to absorb the bitumen and to prevent the 
surface from picking up under traffic. Subsequent applications 
may be made by a pressure distributor or by brooming the tar 
uniformly over the road surface. From one-tenth to one-fifth gal- 
lon per square yard will usually prove sufficient, and this may be 
covered with coarse sand or stone chips which will pass a one-half 
inch laboratory screen. Under favorable conditions a treatment 
should last throughout at least one season. 
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