TC-1. TAR FOR COLD APPLICATION, 



The tar shall be homogeneous. Generah 



It shall meet the following requirements : 



1. Specific gravity 25 V25° C. (77°/77° F.)__not less than 1.100 ^hemfcLrVo'p*- 



2. Specific viscosity at 40° C. (104° F.) 8 to 13 e'^es. 



3. Total distillate by weight : 



To 170° C. (338° F.) not more than 5 per cent 



To 270° C. (518° F.) not more than 30 per cent 



To 300° C. (572° F.) not more than 40 per cent 



4. Total bitumen (soluble in carbon disulphide), 



not less than 90% 

 Tests of the physical and chemical properties of the tar shall Methods of test- 

 be made in accordance with the following methods : "^* 



1. Specific gravity, Department of Agriculture Bulletin 



314, p. 4. 



2. Specific viscosity (on first 50 c.c.) U. S. Department of 



Agriculture Bulletin 314, p. 7. 



3. Distillation test, A. S. T. M. Standard Test D 20-16. 



4. Total bitumen (soluble in carbon disulphide) 



not less than 90% 

 814, p. 25. 



This specification provides primarily for a material to be used 

 as a primer coat on macadam, gravel, or shell roads to be imme- 

 diately followed by a more viscous product (Specification TH-1). 

 It may be used alone for the cold surface treatment of the above 

 types of road in the manner described under Specification TC-2, 

 which provides for a material better adapted to this purpose. It 

 may also be used for the maintenance of tar macadam or tar 

 concrete roads. The specification is intended to cover gas house, 

 coke oven, and water gas tar products. 



If used as a primer coat, the road surface should be in a good 

 state of repair, well consolidated, free from holes or depressions, 

 and thoroughly swept for the removal of dust and detritus be- 

 fore the application is made. Newly constructed or reconstructed 

 roads should be permitted to consolidate under traffic before the 

 tar is applied. The tar may be applied without heating by a 

 pressure distributer at a uniform rate of 0.2 to 0.3 gallon per 

 square yard. The primer coat should be permitted to soak in 

 undisturbed for from 18 to 24 hours, after which it should be 

 given a very light covering of stons chips or fine gravel in just 

 sufficient quantity to prevent the distributor wheels from picking 

 up the surface. The second application should be a heavier tar 

 (Specification TH-1). Roads having a double treatment as above 

 described should yield somewhat longer service than those having 

 only a single treatment. They may be maintained by subsequent 

 hot or cold applications of tar (Specifications TH-1 or TC-2). 



37 



