TP-3. REFINED TAR FOR CONSTRUCTION. 



The refined tar shall be liomogeneous and free from water. General. 

 It shall meet the following requirements : 



1. Specific gravity 25 V25° C. {77V77°F.) 1.150 to 1.200 Physical and 



2. Float test at 50° C. (122° F.) 120 sec. to 150 sec. erti^s!*^ ^'°*" 



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) __97% to 100% Methods of test- 

 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 

 construction of bituminous macadam or one-size-stone bituminous 

 concrete in the northern United States. It is intended to cover 

 refined water-gas tar products. 



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 li inch screen and 

 retained upon a * 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 gi-avel foundation to such depth that it will yield 

 a uniform layer two 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 sliould be applied whenever the wear 

 comes directly upon the wearing course rock. 



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