tests are made. When a single slump test reaches or goes beyond
either the upper or lower action limit, a second test shall
immediately be made. The results of the two tests shall be
averaged and this average used as the slump of the batch to plot
on both the control charts for slump and the chart for range, and
for determining need for any remedial action. Limits shall be set
on separate control charts for slump for each type of mixture.
The upper warning limit shall be set at 12.5 mm 1/2 inch below the
maximum allowable slump specified in paragraph Slump in PART 1 for
each type of concrete and an upper action limit line and lower
action limit line shall be set at the maximum and minimum
allowable slumps, respectively, as specified in the same
paragraph. The range between each consecutive slump test for each
type of mixture shall be plotted on a single control chart for
range on which an upper action limit is set at 50 mm 2 inches.
Samples for slump shall be taken at the mixer. However, the
Contractor is responsible for delivering the concrete to the
placement site at the stipulated slump. If the Contractor's
materials or transportation methods cause slump loss between the
mixer and the placement, correlation samples shall be taken at the
placement site as required by the Contracting Officer, and the
slump at the mixer controlled as directed.
d.
Slump Corrective Action. Whenever points on the control charts
for slump reach the upper warning limit, an adjustment shall
immediately be made in the batch weights of water and fine
aggregate. The adjustments are to be made so that the total water
content does not exceed that amount allowed by the maximum w/c
ratio specified, based on aggregates which are in a saturated
surface dry condition. When a single slump reaches the upper or
lower action limit, no further concrete shall be delivered to the
placing site until proper adjustments have been made. Immediately
after each adjustment, another test shall be made to verify the
correctness of the adjustment. Whenever two consecutive
individual slump tests, made during a period when there was no
adjustment of batch weights, produce a point on the control chart
for range at or above the upper action limit, the concreting
operation shall immediately be halted, and the Contractor shall
take appropriate steps to bring the slump under control.
Additional slump tests shall be made as directed.
e.
Temperature. The temperature of the concrete shall be measured
when compressive strength specimens are fabricated. Measurement
shall be in accordance with ASTM C 1064/C 1064M. The temperature
shall be reported along with the compressive strength data.
f.
Strength Specimens. At least one set of test specimens shall be
made, for compressive or flexural strength as appropriate, on each
different concrete mixture placed during the day for each 380
cubic meters 500 cubic yards or portion thereof of that concrete
mixture placed each day. Additional sets of test specimens shall
be made, as directed by the Contracting Officer, when the mixture
proportions are changed or when low strengths have been detected.
A truly random (not haphazard) sampling plan shall be developed by
the Contractor and approved by the Contracting Officer prior to
the start of construction. The plan shall assure that sampling is
done in a completely random and unbiased manner. A set of test
specimens for concrete with a 28-day specified strength per
paragraph Strength Requirements in PART 1 shall consist of four
SECTION 03300A
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