METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS 15 
(ft) Where possible, samples of sand shall be taken when it is in a damp 
condition. 
(c) If the deposit is worked as a bank or pit and has an open face, the 
sample shall be taken by channeling the open face so as to represent material 
that visual inspection indicates could be used. Care shall be taken to eliminate 
any overburden or stripping at the top or any that has fallen along the face 
from the top. It is necessary, especially in small deposits, to excavate test 
pits some distance back of and parallel to the face to determine the extent of 
the supply. The number and depth of these pits depend on the quantity of 
material that is to be taken from the deposit. Separate samples shall be taken 
from the face of the bank and from test pits. These shall be well mixed in a 
composite sample and the sample for test obtained by the quartering method. 
(d) Deposits that have no open face shall be sampled by means of test pits. 
The number and depth of these will depend on local conditions and the amount 
of material to be used from the source. A separate sample shall be taken 
from each pit and where visual examination indicates no radical difference in 
size of grain, color, etc.. these shall be well mixed in a composite sample and 
the sample for test obtained by the quartering method. Where visual inspec- 
tion indicates a distinct difference in material from different, pits, separate 
samples shall be taken for test. 
(e) It is suggested that the colorimetric test be used for determining the 
percentage of organic material. 6 
15. In addition to the general information accompanying all samples from 
sand and gravel deposits not commercial sources, the same detailed informa- 
tion shall be supplied as with samples of stone taken from local lodges. 
B. COMMERCIAL SAND AND GRAVEL PLANTS 
16. Samples of both sand and gravel from commercial screening or washing 
plants shall be taken from the bins or storage piles, preferably while the ma- 
terial is being loaded from these supplies, or in some other satisfactory manner. 
The sand and gravel shall be sampled as separate units and snipped as such. 
It is difficult to secure a representative sample from stock piles and bins. and. 
if conditions require sampling from these sources, the following is recom- 
mended: Separate samples shall be taken from different parts of the stock pile, 
care being taken to avoid sampling a segregated area of coarse-grained material 
which is likely to exist at the base of the pile. In sampling from a bin, 
separate samples shall be taken from the top and the loading chute. At the 
latter place at least one-half cubic yard of material shall be run off and repre- 
sentative samples taken from it. These separate samples shall be well mixed 
in a composite sample and the sample for test obtained by the quartering 
method. 
17. The size of sand and gravel will be affected by the same factors as 
broken stone and the same inspection is necessary. In addition, the relative 
amount of water used in screening must be taken into consideration. The 
same procedure for taking a sample of broken stone for size is recommended 
for sampling sand and gravel for size, both at plant and at delivery. 
18. Where it is not practical to visit the plant, samples for both quality and 
size shall be taken from different parts of the car or boat during unloading. 
It is recommended that separate samples be taken from the top. middle, and 
bottom of car or boat. These separate samples shall be well mixed in a com- 
posite sample and the sample for test obtained by the quartering method. 
C. QUANTITY OF SAND AND GRAVEL SAMPLES 
19. Samples of run of bank (where the sand and gravel are combined) shall 
consist of at least 100 pounds of material where the gravel content is 50 per 
cent or more of the whole. If the gravel is less in percentage, the sample shall 
be increased in proportion. For exiimple. where the gravel percentage is 25 per 
cent of the whole the sample should contain 200 pounds. 
20. Samples of sand shall contain at least 20 pounds of material. 
21. Samples of gravel shall contain at least 50 pounds of material. 
22. The sample for concrete tesr will depend on the kind of tests to be made 
and the number of specimens necessary. 
G For a description of this test see patre 2S. 
