APPENDIX I. 

 METHODS OF TESTING. 



The following methods of testing are those to which reference is made in the 

 foregoing specifications. In some cases the descriptions from tlie original 

 references have been condensed, but not clianged in any essential particular, 



French CoeflScient of Wear of Rock or Slag. (Bulletin 347, page 5.) — The 

 determination of the French coefficient of wear is made in an apparatus known 

 as the Deval abrasion machine, shown in figure 1. This machine consists 

 essentially of a number of cast-iron cylinders 20 cm. in diameter and 34 cm. 

 deep inside, which are mounted upon a frame in such a manner that the axes 

 of the cylinders are inclined at an angle of 30 degrees with the axis of revo- 

 lution of the frame. The following method is essentially the American Society 

 for Testing Materials Standard Test D2-08. 



The material to be tested is broken into pieces as nearly of the same size 

 and shape as practicable, so that approximately 50 pieces shall weight, after 

 thorough drying, to within 1 gram of 5,000 grams. In no case should the num- 

 ber of pieces exceed 60 or be less than 40. Care should be taken to use only 

 freshly broken fragments, as pieces with rounded edges greatly affect the 

 results. The pieces may be so broken as to average from 2 to 2^ inches in 

 diameter with the assurance of ordinarily obtaining a properly sized sample. 

 After weighing, the sample is placed in one of the cylinders of the Deval 

 machine, the cover bolted on, and the machine given 10,000 revolutions at the 

 rate of 30 per minute. At the conclusion of the test the sample is screened 

 over a laboratory screen having iV-inch square openings, the material retained 

 thoroughly washed free from dust, dried in an oven, and again weighed. The 

 difference between this weight and that first obtained represents the wear as 

 determined by test. 



The following formula, in which " a " represents the final weight of the 

 washed and dried stone, may be used to calculate the French coefficient of wear : 



2000 

 French coefficient of wear = ■ 



5000— 0. 



Toughness of Rock. (Bulletin 347, page 15.) — The following test for tough- 

 ness is essentially the same as the American Society for Testing Materials 

 tentative Standard Test D3-17T. It is made on a cylinder 25 mm. long 

 and from 24 to 25 mm. in diameter, cut from the sample of rock to be tested 

 by means of a diamond drill. In cases where any evidences of lamination or 

 foliation exists, two sets of cores are prepared, one set at right angles to and 

 the other set parallel to the foliations. Specimens a little over 25 millimeters 

 long are next cut from the rock cores by means of a diamond saw. The ends 

 are then ground plane on a grinding lap until they are exactly 25 millimeters 

 long. Although it is not necessary that the two ends of the specimens be 

 exactly parallel, one surface of each at least should be as nearly perpendicular 



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