For conventional concrete mixtures at laboratory temperatures
of 68 to 77°F [20 to 25°C], make the initial test after
an elapsed time of 3 to 4 h after initial contact between cement
and water. Subsequent tests should be made at 1⁄2- to 1-h
intervals. For concrete mixtures containing accelerators, or at
temperatures higher than laboratory, it is advisable to make the
initial test after an elapsed time of 1 to 2 h and subsequent tests
at 1⁄2-h intervals. For concrete mixtures containing retarders, or
at temperatures lower than laboratory, the initial test may be
deferred until an elapsed time of 4 to 6 h. In all cases, time
intervals between subsequent tests may be adjusted as necessary,
depending upon the rate of setting, to obtain the required
number of penetrations.
9.4 Make at least six penetrations for each time-of-setting