General. 



Physical and 

 chemical prop- 

 erties. 



Methods of test- 

 ing. 



TP-6. REFINED TAR FOR CONSTRUCTION. 



The refined tar shall be homogeneous and free from water. 

 It shall meet the following requirements : 



1. Specific gravity 25V25° C. (77V77° F.) 1.200 to 1.250 



2. Float test at 50° C. (122° F.) 150 sec. to 180 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% 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 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 con- 

 struction of bituminous macadam or one-size stone bituminous 

 concrete in the southern 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. 



In one size stone bituminous-concrete construction it should be 

 used in the manner outlined under Specification TP-4. 



In either type of construction the tar should be heated to from 

 250° F. to 300° F. Roads of this character may be maintained 

 with tar surface treatments, using the materials and methods 

 given imder Specifications TC-1. TC-2, or TH-1. Such mainte- 

 nance treatments should be applied whenever the wear comes di- 

 rectly upon the wearing-course rock. 



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