14 BULLETIN 1216, U. S. DEPARTMENT OF AGRICULTURE. 
Method of test. 4. The sample of aggregate shall be room-dry and thoroughly 
mixed. 
5. ("> The measure shall be filled one-third full and the top 
leveled off with the fingers. The mass shall be lamped with the 
pointed end of the tamping rod 25 times, evenly distributed over 
the surface. The measure shall then be filled two-thirds full and 
again tamped -•"» times as before. The measure shall then be filled, 
to overflowing, tamped 25 times, and the surplus aggregate struck 
off, using the tamping rod as a straight edge. 
In tamping the first layer the rod should not be permitted 
forcibly to strike the bottom of the measure. In tamping the 
second and final layers, only enough force to cause the tamping 
rod to penetrate the last Layer of aggregate placed in the measure 
should he used. No effort should be made to rill holes left by the 
rod when the aggregate is damp. 
(h) The net weight of the aggregate in the measure shall be de- 
termined. The unit weight of the aggregate shall then be obtained 
by multiplying the net weight of the aggregate by the factor found 
as described in section 3. 
6. Results with the same sample should check within 1 per cent. 
7. The percentage of voids in the aggregate may be determined 
from the weight per cubic foot and the specific gravity in the usual 
manner. 
TEST FOR ORGANIC IMPURITIES IN SANDS FOR 
CONCRETE. 
(A. S. T. M. standard method, serial designation C 40-22, slightly 
modified.) 
1. The test herein specified is an approximate test for the pres- 
ence of injurious organic compounds in natural sands for cement 
mortar or concrete. The principal value of the test is in furnish- 
ing a warning that further tests of the sand are necessary before 
they are used in concrete. Sands which produce a color in the 
sodium hydroxide solution darker than the standard color should 
be subjected to strength tests in mortar or concrete before use. 
Method of test. -■ (<&) A representative test sample of sand weighing about 1 
pound shall be obtained by quartering or by the use of a sampler. 
(0) A 12-ounce graduated glass prescription bottle shall be 
filled (o the 4$-ounce mark with the sand to be tested. 
(c) A ."» per cent solution of sodium hydroxide (NaOH) in 
water shall be added until the volume of sand and Liquid after 
shaking gives a total volume of 7 liquid ounces. 
i<h The bottle shall be stoppered and shaken thoroughly and 
then allowed to stand for 24 hours. 
(€) A standard color solution shall ho prepared by adding 2.5 
cubic centimeters of a 2 per cent solution of tannic acid in 10 per 
rout alcohol to 'J-o cubic centimeters of a ."» per cent sodium hy- 
droxide solution. This shall be placed in a I'i-ouneo prescription 
bottle, Stoppered, and allowed to stand for 24 hours, then 25 cubic 
< entimeters of water added. 
(f) The color of the clear liquid above the sand shall be com- 
pared with the standard color solution prepared as in paragraph 
i' i or with a glass of color similar to tin 1 standard solution. 
::. Solutions darker in color than the standard color have a 
"color value" higher than 250 parts per million in terms of 
tannic acid. 
Note. — Special attention is called to the fact that this test is a 
Warning that additional tests of the sand may he necessary. 
COMPRESSION AND TENSION TESTS OF FINE AGGREGATE 
FOR CONCRETE. 
1. Fine aggregate shall be tested for strength either by tension 
or compression in a mortar proportioned either by volume or by 
weight, using a 1 : 3 mix. 
