The times for the tests shall be selected randomly within the 8-hour
period. An additional test shall be made whenever the slump is shown
to be out of control or excessive variation in workability is reported
by the placing foreman. When an electric moisture meter is operating
satisfactorily, at least two direct measurements of moisture content
shall be made per week to check the calibration of the meter. The
results of tests for moisture content shall be used to adjust the added
water in the control of the batch plant.
e. Moisture Content Corrective Action - Whenever the moisture content
of the fine aggregate changes by 0.5 percent or more, the scale
settings for the fine-aggregate batcher and water batcher shall be
adjusted (directly or by means of a moisture compensation device).
3.8.2.2
Coarse Aggregate
a. Grading - At least once during each shift in which the concrete
plant is operating, there shall be a sieve analysis in accordance with
ASTM C 136 for each size of coarse aggregate. The location at which
samples are taken may be selected by the Contractor as the most
advantageous for production control. However, the Contractor shall be
responsible for delivering the aggregate to the mixer within
specification limits. A test record of samples of aggregate taken at
the same locations shall show the results of the current test as well
as the average results of the five most recent tests including the
current test. The Contractor may adopt limits for control coarser than
the specification limits for samples taken other than as delivered to
the mixer to allow for degradation during handling. When facilities
are available to test samples five times as large as those required in
ASTM C 136, no averaging shall be done.
b. Corrective Action for Grading - When the amount passing any sieve
is outside the specification limits, the coarse aggregate shall be
immediately resampled and retested. If the second sample fails on any
sieve, that fact shall be reported. Where two consecutive averages of
five tests (or two consecutive tests where large samples are used) are
outside specification limits, the operation shall be considered out of
control, and that fact shall be reported, concreting shall be stopped,
and immediate steps shall be taken to correct the grading.
c. Coarse Aggregate Moisture Content - A test for moisture content of
each size group of coarse aggregate shall be made at least once a
shift. When two consecutive readings for smallest size coarse
aggregate differ by more than 1.0 percent, frequency of testing shall
be increased to that specified previously for fine aggregate.
d. Coarse Aggregate Moisture Corrective Action - Whenever the moisture
content of any size of coarse aggregate changes by 0.5 percent or more,
the scale setting for the coarse aggregate batcher and the water
batcher shall be adjusted to compensate for this.
e. Particle Shape Testing - When directed, a problem exists in
connection with aggregate particle shape, tests shall be made in
accordance with ASTM D 4791. Testing frequency shall be not less than
one per day, when directed.
f. Particle Shape Corrective Action - When testing for particle shape
is required, two consecutive failures in the same sieve size shall be
immediately reported, who shall determine what corrective action is
SECTION 03700
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