General. 
Physic 
chemical 
erties. 
1 and 
prop- 
Methods of 
ing. 
test- 
TP-2. REFINED TAR FOR CONSTRUCTION. 
The refined tar shall be homogeneous and free from water. 
It shall meet the following requirements: 
1. Specific gravity 25° C./25 C. (77°/77° F.) 1.200 to 1.250 
2. Float test at 50° C. (122° F.) 90 sec. to 120 sec. 
3. Total distillate by weight: 
To 170° C. (338° F.) ___not more than 1.0 per cent 
To 270° C. (518° F.) not more than 10.0 per cent 
To 300° C. (572° F.) not more than 20.0 per cent 
a. Melting point of residue__not more than 65° C. (149° F.) 
4. Total bitumen (soluble in carbon disulphide), 
80 per cent to 97 per cent 
Tests of the physical and chemical properties of the refined tar 
shall be made in accordance with the following methods : 
1. Specific gravity, U. S. Department of Agriculture Bulletin 
314, p. 5. 
2. Float test, U. S. Department of Agriculture Bulletin 314, p. 9. 
3. Distillation test, A. S. T. M. Standard Test D 20-16. 
a. Melting point A. S. T. M. Tentative Standard D 36-16 T, 
Proc A. S. T. M., 1916, 549. 
4 Total bitumen, U S Department of Agriculture Bulletin 314, 
p. 25. 
This specification provides for a material to be used in the con- 
struction of bituminous macadam in the extreme northern United 
States. It is intended to cover refined gas-house or coke-oven tar. 
It should be applied at a temperature of from 250° F. to 300° 
F. to the upper or wearing course of compacted broken stone at 
the rate of from 1| to If gallons per square yard. The applica- 
tion may be made by means of pouring pots or by a pressure dis- 
tributor so designed that it will not produce ruts during applica- 
tion. The above quantities are based on a wearing course 3 inches 
in thickness before rolling, composed of a product which will pass 
a 2 to 3 inch laboratory screen and be retained on a 1-inch labo- 
ratory screen. The exact range in size should be governed by the 
kind and quality of rock used. The application should be fol- 
lowed by a sufficient amount of clean small sized broken stone to 
fill the surface voids when thoroughly rolled. A seal coat of the 
same tar or of hot asphalt (Specification OA-6) should then be 
applied at the rate of 0.4 to 0.6 gallon per square yard and cov- 
ered with a sufficient amount of stone chips to just absorb the 
excess bitumen. Roads of this character may be maintained with 
tar surface treatments, using the materials and methods given un- 
der specifications TC-1, TC-2, or TH-1. Such maintenance treat- 
ments should be applied whenever the wear comes directly upon 
the wearing course rock. 
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