TP-4. REFINED TAR FOR CONSTRUCTION. 
General. 
Physical and 
chenixcal prop- 
erties. 
Methods of test- 
ing. 
The refined tar shall be homogeneous and free from water. 
It shall meet the following requirements : 
777° F.) 1.200 to 1.250 
120 sec. to 150 sec. 
1. Specific gravity 25°/25° C. (77' 
2. Float test at 50° C. (122° F.)_ 
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% to 97% 
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 tests, A. S. T. M. Standard Test D20-16. 
a. Melting point, A. S. T. M. Tentative Standard D36- 
16 T, Proc. A. S. T. M. 1916, p. 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 or one size stone bituminous 
concrete in the northern United States. It is intended to cover 
refined gas-house or coke-oven tar. 
In bituminous macadam construction it should be applied in 
the manner outlined under Specification TP-2. 
One-size stone bituminous concrete contemplates a mixture of 
the tar with a crusher product passing a lj-inch screen and re- 
tained upon a one-half-inch screen. The tar should be heated to 
a temperature of from 225° F. to 275° F. and the crushed stone 
to a temperature of from 150° F. to 250° F. before mixing. The 
mixture should contain from 5 per cent to 7 per cent bitumen, 
and will vary within these limits with the character of the rock 
and the exact grading of the aggregate. The hot mixture should 
be deposited in a uniform layer over a concrete or well compacted 
broken stone or gravel foundation to such depth that it will yield 
a uniform layer 2 inches in thickness after thorough rolling. 
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 covered with a sufficient amount of stone chips to just 
absorb the excess bitumen. Roads of this character may be main- 
tained with tar surface treatments, using the materials and 
methods given under Specifications TC-1, TC-2, or TH-1. Such 
maintenance treatments should be applied whenever the wear 
comes directly upon the wearing-course rock. 
44 
