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 from the previous
sample, the scale settings for the fine aggregate batcher and water
batcher shall be adjusted (directly or by means of a moisture
compensation device).
3.10.2.2
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 to the Contracting Officer. 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 to
the Contracting Officer, 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
from the previous sample, the
scale setting for
the coarse aggregate
batcher and the water batcher
shall be adjusted
to compensate for this.
e. Material Finer than the 75 m No. 200 Sieve - When in the opinion
of the Contracting Officer, a problem exists in connection with the
cleanliness of the coarse aggregate, tests shall be made in accordance
with ASTM C 117. Testing frequency shall be as directed.
f. Corrective Action for material finer than the 75 m No. 200 Sieve -
When material finer than the No. 200 sieve exceeds 1.0 percent of the
weight of the coarse aggregate finer than 37.5 mm 1-1/2 inch or 0.5
percent of the weight of the aggregate coarser than 37.5 mm 1-1/2 inch,
the Contracting Officer shall be notified, and steps, such as washing
or other corrective action, shall be initiated immediately.
SECTION 03701
Page 60
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