36 BULLETIK 704, U. S. DEPAETMENT OF AGRICULTURE. 



l)e omitted in cases where material from a well-liiiown source of supply lias 

 been tested within one year previous to the date of acceptance or rejection. In 

 such case the report of the last previous test may be used as the basis of ac- 

 ceptance or rejection. Mixed samples may be taken Avhen deemed necessary. 

 Each sample should weigh at least 2.5 pounds and be composed only of sound 

 interior rock strictly representative of that which it proposed to use. The 

 fragments should be 2 inches in size or larger. In addition, one piece which 

 should measure at least 3 by 4 by 6 inches will be required if a toughness test 

 is to be made. This piece should be free from seams and cracks, and should 

 have the bedding plane marked if practicable. Samples should be shipped in 

 tight boxes or heavy burlap bags. 



Sampling for Size or Grading. — Broken stone may be sampled for size at 

 the crusher, from bins, cars, or storage piles on the job. A composite sample 

 composed of samples from different parts of the supply is advisable. Samples 

 should weigh not less than 10 pounds for material containing fragments f 

 inch in diameter. Samples of larger aggregates should increase in size up to 

 about 60 pounds, depending upon the diameter and weight of the largest frag- 

 ments present. When laboratory tests for size are required, samples should be 

 shipped in tight boxes or heavy close canvas bags. 



BROKEN SLAG. 



Sampling for Quality. — Slag should be sampled from the crusher or that poi*- 

 tion of the dump which it is proposed to use, at least two weeks and not more 

 than one month before final acceptance. Additional samples should be taken 

 during progress of the work, whenever the quality or appearance of the slag 

 changes, and at such other times as may be directed. For the French co- 

 efficient of wear determination, each sample should weigh at least 25 pounds 

 and be composed of fragments 2 inches in size or larger. Samples of approxi- 

 mately 100 pounds of each size will be needed for determinations of weight per 

 cubic foot, but such test should ordinarily be made at the crusher or on the job. 

 Tight boxes or heavy burlap bags should be used as containers when shipping 

 samples of slag. 



Sampling for Size or Grading. — The same directions given under broken 

 stone apply to broken slag. 



GRAVEL. 



Samples of pit run gravel proposed for use in water-bound gravel road con- 

 struction should be taken at least 10 days and not more than 6 months prior 

 to the date of acceptance or rejection, and, if from an accepted source of supply, 

 whenever, during the progress of the work, the gravel appears to change 

 markedly in either quality or grading. Great care should always be exercised 

 in sampling a gravel pit to insure obtaining material for test which is strictly 

 representative of that which it is proposed to use. A number of samples may 

 be taken from a single pit if necessary to cover the probable range in grading 

 of the available material. Samples of pit run gravel should weigh from 50 to 

 75 pounds. 



Samples of screened gravel may be taken at the plant, from bins, storage 

 piles, barges, or cars. A composite sample composed of samples from diiferent 

 parts of the supply is advisable in order to determine the average composi- 

 tion of the material. Every shipment of gi'avel for bituminous concrete or 

 Portland cement concrete should be sampled, in which case no single sample 

 sliould represent over 100 cubic yards. Samples should weigh from not less 



