Sand—Sand must be clean, dry, uniform in density and
grading, uncemented, durable, and free-flowing. Any gradation
may be used that has a uniformity coefficient (Cu 5 D60/D10)
less than 2.0, a maximum particle size smaller than 2.0 mm
(No. 10 sieve), and less than 3 % by weight passing 250 μm
(No. 60 sieve). Uniformly graded sand is needed to prevent
segregation during handling, storage, and use. Sand free of
fines and fine sand particles is required to prevent significant
bulk-density changes with normal daily changes in atmospheric
humidity. Sand comprised of durable, natural subrounded,
or rounded particles is desirable. Crushed sand or
sand having angular particles may not be free-flowing, a
condition that can cause bridging resulting in inaccurate
density determinations (see Note 3). In selecting a sand from a
potential source, a gradation and bulk-density determinations
in accordance with the procedure in Annex A2 should be made
on each container or bag of sand. To be an acceptable sand, the
bulk-density variation between any one determination shall not
be greater than 1 % of the average. Before using sand in
density determinations, it shall be dried, then allowed to reach
an air-dried state in the general location where it is to be used
(see Note 4). Sand shall not be re-used without removing any
contaminating soil, checking the gradation, drying and redetermining
the bulk-density (see Note 5). Bulk-density tests of
the sand will be made at time intervals not exceeding 14 days,
always after any significant changes in atmospheric humidity,
before reusing, and before use of a new batch from a
previously approved supplier (see Note 6).