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 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 chart for
slump reach the upper warning limit, an adjustment shall be immediately
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 water-cement ratio specified, based upon
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 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. Also, additional
slump tests shall be made as directed. All this shall be at no
additional cost to the Government.
e. Compressive Strength - At least once during each shift, the
Contractor shall fabricate and cure, in accordance with ASTM C 192/C
192M, four 150 by 300 mm 6 by 12 inch test specimens. Two specimens
shall be tested at 7 days and two at 28 days. If pozzolan is used, six
specimens shall be fabricated and two tested at 7 days, two at 28 days,
and two at 90 days. Testing shall be in accordance with ASTM C 39/C 39M.
The results of compressive strength tests will not be used for
acceptance. Results will be for record purposes and to evaluate the
uniformity of concrete production. The results of each set of
specimens tested at each age shall be averaged to produce one "test
result". These "test results" shall be plotted on control charts for
each age. One control chart shall consist of each "test result"
plotted consecutively. One control chart shall consist of the range
from the "test result" for any one day to that of the next day. When
the range exceeds 6.9 MPa 1,000 psi, the Contracting Officer shall be
notified and the operation modified to produce better uniformity.
f. 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.
3.4.2.8
Placing
a. Preparation for Placing - Each section of wall shall be inspected
in sufficient time prior to concrete placement by the Contractor to
certify to the Contracting Officer that it is ready to receive
concrete. The results of each inspection shall be reported in writing.
b. Placing - The placing foreman shall supervise all placing
operations, shall determine that the correct quality of concrete is
placed in each location as directed by the Contracting Officer, and
SECTION 03373
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