36 BULLETIN 555, U. S. DEPARTMENT OF AGRICULTURE. 



the plates. The moist clay covers the wire on one plate, and the other plate is 

 squeezed down tightly on the wire. After drying, the one plate being held firmly 

 against cleats, wire slings are run symmetrically from the ends of the upper 

 plate to one arm of a beam balance, and the tension necessary to separate the 

 plates is given by shot or weights in the other pan of the balance. This test is 

 tedious and is of service chiefly on low-grade samples which are of doubtful 

 efficiency, but which represent the only available material for local construction. 



(d) Approximate tests for tenacity of mixture can be made as follows: 



Make cylinders from the material passing the 10-mesh sieve, 25 mm. by 25 mm. 

 The material is worked into a stiff mud and molded under 132 kg. per sq. cm. 

 pressure. Dry thoroughly at 100° O. (212° F.) and break by the small Page 

 impact machine for testing cementing value, using a 1 kg. hammer and 1 cm. 

 drop. Record the number of strokes as the relative measure of tenacity. 



Mix 50 grams of the material passing the 10-mesh sieve with grams 



of water and knead with the hands into a spherical ball. Measure the diameter. 



Let this ball drop from a height of cm. on a flat slab. Measure and 



record the reduction in diameter and examine the surface for cracks. 



Usually the plastic character and adhesiveness of a good road soil can be 

 judged by the feeling of the mud made from this material, its adherence to 

 the hands, and its stretch under light pulling. 



TESTS OF PHYSICAL AND CHEMICAL PROPERTIES OF BITUMINOUS 



MATERIALS. 



(13) Specific Gbavity: Standardized hydrometers or pycnometers. U. S. 

 Department of Agriculture Bulletin 314, pp. 4 to 7. 



(14) Flash Point (Open Cup) : U. S. Department of Agriculture Bulletin 

 314, p. 17. 



(15) Melting Point: A. S. T. M. tentative standard D36-16T; Proc. A. S. 

 T. M. 1916, p. 549. 



(16) Ductility: A. S. C. E. 1914 Proceedings, p. 3047. 



(17) Penetration: A. S. T. M. standard test D5-16. 



(18) Float Test: U. S. Department of Agriculture Bulletin 314, p. 9. 



(19) Specific Viscosity (on First 50 c.c.) : U. S. Department of Agriculture 

 Bulletin 314, p. 7. 



(20) Total Bitumen and Organic and Inorganic Matter Insoluble in 

 Carbon Disulphide: U. S. Department of Agriculture Bulletin 314, p. 25. 



(21) Bitumen Insoluble in Naphtha: U. S. Department of Agriculture Bul- 

 letin 314, p. 2S. 



(22) Volatilization Test (Loss at 163° C. or Other Temperature) : U. S. 

 Department of Agriculture Bulletin 314, p. 19, except that a 50-gram sample is 

 used in a flat-bottom box 55 mm. diameter by 35 mm. deep (Gill style, 3-ounce 

 deep pattern box). 



(23) Distillation Test: A. S. T. M. standard test D20-16. 



(24) Fixed Carbon: U. S. Department of Agriculture Bulletin 314. p. 30. 



(25) Dimethyl Sulphate Test: U. S. Department of Agriculture Bulletin 

 314, p. 25. 



(26) Percentage of Residue of Penetration : 



Fifty grams of the oil are placed in a 3-ounce deep, seamless tin box ; the 

 box is placed in a sand bath and heated over a Bunsen burner. A thermom- 

 eter is suspended in the oil, the bulb not touching the bottom of the box. The 

 temperature of the oil is kept at from 249° C, (480° F.) to 260° C. (500° F.), 

 and the oil is stirred from time to time with the thermometer to prevent over- 



