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 25V25° C. (77V77° F.) 1.150 to 1.200 Ss.'"^ ^^''^' 



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 : *"*• 



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 i*ate of from IJ 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. 



41 



