32 BULLETIN 555, U. S. DEPARTMENT OF AGRICULTURE. 



The difference between the original weight of the sample and its weight 

 after 24 hours immersion is used to determine the absorption. 



(6) Weight pee Cubic Foot Test, Stag: 



The dried slag shall be shaken to refusal in a cubic-foot measure or other 

 suitable container, and its weight determined. 



(7) Mortar-Strength Test, Screenings and Sand: A. S. T. M. Standard test 

 C9-17. 



SIZE, GRADING, OR MECHANICAL ANALYSIS OF STONE, SLAG, 



GRAVEL, SAND. 



(8) Test of Size or Grading of Coarse Aggregate, Stone, Slag, and Gravel: 

 A sample of the material weighing not less than fifty (50) times the weight 



of the largest size stone present is to be used. After drying at not over 110°C. 

 (230°F.) to constant weight the sample is passed through such of the following 

 size screens, having circular openings, as are required or called for by the speci- 

 fications, screens to be used in the order na: led : 35-inch, 3-inch, 2i-inch, 

 2-inch, lj-inch, 1-inch, f-inch, 2 -inch, and ^-inch. 



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

 mechanical analysis is recorded in the following manner : 



Per cent. 



Passing 33-inch screen and retained on 3-inch screen 



Passing 3-inch screen and retained on 2Mnch screen 



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



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



Passing 1-inch screen 



100 



(9) Washing Test and Mechanical Analysis, Road Gravel: 



A sample of the material weighing not less than 50 times the weight of the 

 largest size stone present is to be used. After thoroughly drying at 100° C. 

 (212° F.) in a hot-air bath, the sample is cooled, weighed, and placed in a 

 shallow pan, covered with water, and thoroughly agitated by means of a trowel 

 for 15 seconds. After 15 seconds sedimentation the water is poured off through 

 a 200-mesh sieve, and the operation of agitation, sedimentation, and decantation 

 repeated until the wash water is approximately clear after 15 seconds. The 

 washed material, together with any residue retained on the 200-mesh sieve, is 

 then dried to constant weight, cooled and weighed and passed through such of 

 the following size screens and sieves as are called for in the specification, using 

 them in the order named. 



Screens (circular openings) : 3-inch, 23-inch, 2-inch. 14-inch. 1-inch, ij-inch. 

 2-inch, and J-inch. 



Sieves A. S. T. M. standard method D7-16 (square mesh) : 10. 20, 30. 40. 50, 

 60, 80, 100, and 200 meshes per linear inch. 



The percentage by weight retained on each screen or sieve and based on the 

 weight of the original sample is calculated, using for the determination of the 

 percentage of material passing the 200-mesh sieve the sum of the weights of 

 material passing this sieve by analysis and by washing. 



(10) Elutriation Test, Sand or Fine Aggregate: 



The entire sample is moistened and thoroughly mixed, and a sample weigh- 

 ing approximately 105 * grams is obtained for elutriation and grading by 

 quartering or by selecting small portions from various parts of a fiat pile. 

 The sample is then dried at not over 110° C. (230° F.). This dried sample 

 is accurately weighted and placed in a 500-cc. 1 beaker, and about 350 cc. 1 of 



