General. 



Physical and 

 chemical prop- 

 erties. 



Methods of test- 

 ing. 



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. (77V77° 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 2.50° 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 suflicient 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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