SAMPLING AND TESTING HIGHWAY MATERIALS. 7 



(a) A cast-iron anvil weighing not less than 50 kg., firmly fixed upon a solid founda- 

 tion; 



(b) A hammer weighing 2 kg., arranged so as to fall freely between suitable guides; 



(c) A plunger made of hardened steel and weighing 1 kg., arranged to slide freely 

 in a vertical direction in a sleeve, the lower end of the plunger being spherical in 

 shape with a radius of 1 cm.; 



(d) Means for raising the hammer and for dropping it upon the plunger from any 

 specified height from 1 to not less than 75 cm., and means for determining the height 

 of fall to approximately 1 mm.; 



(e) Means for holding the cylindrical test specimen securely on the anvil without 

 rigid lateral support and under the plunger in such a way that the center of its upper 



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Fig. 5.— Details of grinding lap. 



surface shall throughout the test be tangent to the spherical end of the plunger at its 

 lowest point. 



(6) The test shall consist of a 1 cm. fall of the hammer for the first blow, a 2 cm. 

 fall for the second blow, and a fall increasing by 1 cm. for each succeeding blow until 

 failure of the test specimen occurs. 



(7) The height of the blow in centimeters at failure shall be the toughness of the test 

 specimen. The individual and the average toughness of three test specimens shall 

 be reported when no plane of structural weakness is apparent. In cases where a plane 

 of structural weakness is apparent, the individual and average toughness of the three 

 specimens in each set shall be reported and identified. Any peculiar condition of a 

 test specimen which might affect the result, such as the presence of seams, fissures, 

 etc., shall be noted and recorded with the test result. 



5. TESTS FOR APPARENT SPECIFIC GRAVITY AND ABSORPTION OF 

 STONE OR OTHER COARSE MATERIALS. 



(1) The apparent specific gravity shall be obtained by weighing the water dis- 

 placed by a sample of the material weighing approximately 1,000 grams, broken into 

 pieces about \\ inches in diameter. The vessel to be used is shown in figure 7. It 

 consists of a galvanized-iron cylinder closed at one end and measuring 5 inches in 

 diameter by 8 inches high. A brass spout J inch in diameter is soldered into 



