TP-1. REFINED TAR FOR CONSTRUCTION. 
The refined tar shall be homogeneous and free from water. General. 
It shall meet the following requirements: Physical and 
1. Specific gravity 25°/25° C. (77°/77° F.) 1.150 to 1.200 fgg? 1 prop - 
2. Float test at 50° C. (122° F.) 90 sec. to 120 sec. 
3. Total distillate by weight: 
To 170° C. (336° 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)__97% to 100% 
Tests of the physical and chemical properties of the refined Methods of test- 
tar shall be made in accordance with the following methods : ln *» 
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— 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 
construction of bituminous macadam in the extreme northern 
United States. It is intended to cover refined water-gas tar prod- 
ucts. 
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 11 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 appli- 
cation. 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 laboratory screen. The exact range in size should be gov- 
erned by the kind and quality of rock used. The application 
should be followed 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 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. 
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