FORMS FOE SPECIFICATIONS, ETC., FOR ROAD MATERIALS. 
31 
When the material has a specific gravity below 2.20 a total weight of 4,000 
grams instead of 5,000 grams shall be used in the abrasion test. 
(3) Toughness Test, Stone: United States Department of Agriculture Bulle- 
tin 347, page 15. 
(4) Haedness Test, 1 Stone and Stone Block; United States Department of 
Agriculture Bulletin 347, page 10. 
(5) Spectftc Gravity and Absorption Tests, Stone: 
The apparent specific gravity is obtained by weighing the water displaced 
by a sample of the material weighing approximately 1,000 grams, broken into 
pieces about li inches in diameter. (The vessel used is shown in figure 1.) 
**2I Galvanized 
Iron 
Note: Notch is filed across 
lower end of spout ±/i$k" (2°) 
to prevent drip.^=n .- =Lj~ 
Xfhree lugs soldered on) 
bottom symmetrically. 
Fig. 1. — Vessel used in making specific-gravity and absorption tests. 
It consists of a galvanized-iron cylinder closed at one end, and measuring 
5 inches in diameter by 8 inches high. A brass spout £ inch in diameter is 
soldered into the side of the cylinder, 6 inches from the bottom. The spout 
is inclined at an angle of 2° with the horizontal and is 2J inches long. A 
notch is filed across its lower end, as shown, to stop the drip from the dis- 
placed water. In determining the specific gravity, the dried and cooled 
sample is weighed to the nearest 0.5 gram and immersed in water for 24 
hours. The pieces are then individually surface-dried with a towel, the sample 
reweighed, and immediately placed in the cylinder, which has been previously 
filled to overflowing with water at room temperature. 
The weight of water displaced by the sample is used to calculate its apparent 
specific gravity. 
1 It is recommended that the laboratories cooperate with the view of devising an im- 
proved method for the determination of the hardness of rock, especially in regard to the 
character of the abrasive used. 
