30 BULLETIN "tOi, U. S. DEPARTMENT OF AGRICULTTJRE. 



Size, Grading, or Mechanical Analysis of Broken Stone, Broken Slag, or 

 Gravel. (Bulletin 555, page 32 (S).) — A sample of tbe material weighing not 

 less than tifty (50) times the weight of the largest size stone present is used. 

 After drying at not over 110° C. (230° F.) to constant weight, the samijle is 

 passed through such of the following size screens, having circular openings, 

 as are required or called for by the specifications, screens to be used in the 

 order named : 3A-inch, 3-inch, 2^-inch, 2-inch, li-inch, 1-inch, f -inch, ^-inch, and 

 :J-inch. 



The percentage by weight, retained on each screen, is determined and the 

 mechanical analysis is recorded in the following manner : 



Per cent. 



Passing 3J-inch screen and retained on 3-inch screen 



Passing 3-ineh screen and retained on 2 J-inch screen 



Passing 21-inch screen and retained on 2-inch screen 



Passing ^-inch screen and retained on J-inch screen 



Passing 1-inch screen 



Elutriation Test of Sand. (Bulletin 555, page 32.) — The entire sample is 

 moistened and thoroughly mixed, and a sample weighing approximately 105 ^ 

 grams is obtained for elutriation and grading by quartering or by selecting 

 small portions from various parts of a flat pile. The sample is then dried at 

 not over 110° C. (230° F.). This dried sample is accurately weighed and placed 

 in a 500-cc.^ beaker, and about 350 cc.^ of water is added and agitated in such 

 manner that no whirling results. After settling for 20 seconds, the water is 

 poured off through a 200-raesh sieve, and the operation of agitation, sedimen- 

 tation, and decantation repeated until the wash water is approximately clear. 

 Particles caught on the 200-mesh sieve are then washed back into the washed 

 sample remaining in the beaker. The entire washed sample is dried to con- 

 stant weight and accurately weighed, and the 



Original weight — Final weight 



Per cent by elutriation = ; X 100. 



Original weight 



Mechanical Analysis or Grading of Sand or Fine Aggregate. (Bulletin 

 555, page 33.) — All of the dried sample remaining after the elutrition test, if 

 such is required, is passed successively through tbe desired screens and sieves, 

 beginning with either the largest or smallest as may be convenient. Where an 

 elutriation test is not required, a dried sample of the original material weighing 

 about 100 grams is used. 



The percentage, by weight, of the unwashed sample retained on each screen 

 is determined, and the mechanical analysis is recorded according to one or 

 both of the following methods. A screen with ^-inch circular openings is used, 

 together with square-mesh sieves as specified in A. S. T. M. Standard Methods 



D7-16. 



Per cent. 



Total retained on i-inch screen 



Passing i-inch screen and retained on 10-mesh sieve 



Passing 10-mesh sieve and retained on 20-mesh sieve 



Passing 20-mesh sieve and retained on 30-mcsh sieve 



Passing 30-mesh sieve and retained on 40-mesh sieve. 



Passing 40-mesh sieve and retained on 60-mesh sieve 



Passing 50-mesh sieve and retained on 80-mesh sieve 



Passing 80-mesh sieve and retained on 100-mcsh sieve 



Passing 100-mesh sieve and retained on 200-mesh sieve 



Passing 200-mesh sieve 



Total 100 



1 If the sand is so coarse that a 100-gram sample is not sunicient, the size of the sample, the container, 

 and the amount of water used may bo proportionately increased. 



