14 BULLETIN 9i9, U. S. DEPARTMENT OF AGRICULTURE. 



12. TESTS FOR DETERMINING THE AMOUNT OF CLAY AND SILT IN SAND 

 OR FINE AGGREGATE, IN GRAVEL AND IN SAND-CLAY, TOP SOIL, OR 

 SEMIGRAVEL. 



A. SAND OR FINE AGGREGATE. 



(1) The specification covers the determination of the quantity of clay and silt in 

 natural sand to be used in road construction. 



(2) The sample as received shall be moistened and thoroughly mixed, then dried 

 to constant weight at a temperature between 100° C. (212° F.) and 110° C. (230° F.). 



(3) Five hundred (500) grams representative of the dried sample shall be placed in 

 a dried and accurately weighed pan or vessel having vertical sides and provided with 

 a pouring lip. This pan shall be substantially 22.9 cm. (9 inches) in diameter by 

 not less than 10.2 cm. (4 inches) deep. Pour sufficient water in the pan to cover 

 the sand (about 225 c. c). Agitate vigorously for fifteen (15) seconds. Allow to 

 settle for fifteen (15) seconds and then pour off the water into a tared evaporating 

 dish, taking care not to pour off any sand. Repeat until the wash water is clear, using 

 a glass rod to stir the material for the last few washings. 



(4) Thoroughly dry the pan and washed sand in an oven at between 100° C. (212° 

 F.) and 110° C. (230° F.), weigh and determine net weight of sand. 



(5) Compute the per cent of clay and silt as follows: 



Original weight— weight after washing ..,__ , , , .._. 



rT. ■ — i — . , . 5 Xl00=per cent of clay and silt. 



Original weight * J 



For a check on the results, evaporate the wash water to dryness and weigh the 



residue. 



Weight of residue .,..-,. , . , ... 



,-, . ■ — | r-T— X100=per cent of clay and silt. 



B. GRAVEL. 



(6) The specification covers the determination of the quantity of clay and silt in 

 natural gravel to be used in road construction. 



(7) The sample as received shall be moistened and thoroughly mixed, then dried 

 to constant weight at a temperature between 100° C. (212° F.) and 110° C. (230° F.). 



(8) A representative portion of the dry material, weighing not less than 50 times 

 the weight of the largest stone in the sample, shall be selected from the sample, and 

 placed in a dried and accurately weighed pan or vessel. The pan shall be 30.2 cm. 

 (12 inches) in diameter by not less than 10.2 cm. (4 inches) deep, as nearly as may 

 be obtained. Pour sufficient water in the pan to cover the gravel and agitate vigor- 

 ously for fifteen (15) seconds, using a trowel or stirring rod. Allow to settle for fifteen 

 (15) seconds, and then pour off the water into a tared evaporating dish, being careful 

 not to pour off any sand. Repeat until the wash water is clear. 



(9) Dry the washed material to constant weight in an oven at between 100° C. 

 (212° F.) and 110° C. (230° F.), weigh, and determine net weight of gravel. 



(10) Compute the per cent of clay and silt as follows: 



Original weight— weight after washing. ,,_- , , . .._, 



— g ~ . P . r-|- ~ X100=per cent of clay and silt. 



Original weight J 



C. SAND-CLAY, TOP SOIL, AND SEMIGRAVEL. 



(11) Dry 500 grams of the material at a temperature below 350° F. (176.6° C.) to 

 a constant weight. Gently pulverize to break down soft clods or masses, but not to 

 grind or break hard material. Pass through a 10-mesh sieve, weigh the coarse residue, 

 and record as "coarse material." Use the material passing the 10-mesh sieve as the 

 starting point of a percentage analysis as follows: 



(12) Weigh out two samples of 50 grams of this material for duplicate analysis. 

 Place each in a tared wide-mouth bottle (5 to 6 cm. diameter and about 12 to 15 cm. 



