specimens, two to be tested at 7 days and two at 28 days. [A set
of test specimens for concrete with a 90-day strength per the same
paragraph shall consist of six specimens, two tested at 7 days,
two at 28 days, and two at 90 days.] Test specimens shall be
molded and cured in accordance with ASTM C 31/C 31M and tested in
accordance with ASTM C 39/C 39M for test cylinders and ASTM C 78
for test beams. Results of all strength tests shall be reported
immediately to the Contracting Officer. Quality control charts
shall be kept for individual strength "tests", ("test" as defined
in paragraph Strength Requirements in PART 1) moving average of
last 3 "tests" for strength, and moving average for range for the
last 3 "tests" for each mixture. The charts shall be similar to
those found in ACI 214.3R.
3.17.6
Inspection Before Placing
Foundations, construction joints, forms, and embedded items shall be
inspected by the Contractor in sufficient time prior to each concrete
placement in order to certify to the Contracting Officer that they are
ready to receive concrete. The results of each inspection shall be
reported in writing.
3.17.7
Placing
The placing foreman shall supervise placing operations, shall determine
that the correct quality of concrete or grout is placed in each location as
specified and as directed by the Contracting Officer, and shall be
responsible for measuring and recording concrete temperatures and ambient
temperature hourly during placing operations, weather conditions, time of
placement, volume placed, and method of placement. The placing foreman
shall not permit batching and placing to begin until it has been verified
that an adequate number of vibrators in working order and with competent
operators are available. Placing shall not be continued if any pile of
concrete is inadequately consolidated. If any batch of concrete fails to
meet the temperature requirements, immediate steps shall be taken to
improve temperature controls.
3.17.8
Vibrators
The frequency and amplitude of each vibrator shall be determined in
accordance with COE CRD-C 521 prior to initial use and at least once a
month when concrete is being placed. Additional tests shall be made as
directed when a vibrator does not appear to be adequately consolidating the
concrete. The frequency shall be determined while the vibrator is
operating in concrete with the tachometer being held against the upper end
of the vibrator head while almost submerged and just before the vibrator is
withdrawn from the concrete. The amplitude shall be determined with the
head vibrating in air. Two measurements shall be taken, one near the tip
and another near the upper end of the vibrator head, and these results
averaged. The make, model, type, and size of the vibrator and frequency
and amplitude results shall be reported in writing. Any vibrator not
meeting the requirements of paragraph Consolidation, shall be immediately
removed from service and repaired or replaced.
3.17.9
Curing Inspection
a.
Moist Curing Inspections. At least once each shift, and not less
than twice per day on both work and non-work days, an inspection
shall be made of all areas subject to moist curing. The surface
SECTION 03300A
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