3.3.1
Measuring
Make measurements at intervals as specified in paragraphs entitled
"Sampling" and "Testing."
Adjust batch proportions to replicate the mixture design using methods
provided in the approved quality assurance plan. Base the adjustments on
results of tests of materials at the batch plant for use in the work.
Maintain a full record of adjustments and the basis for each.
3.3.2
Mixing
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NOTE: For SOUTHWESTNAVFACENGCOM projects located a
t Marine Corps Base, Camp Pendleton, California,
delete the first bracketed sentence.
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ASTM C 94 and ACI 301. Machine mix concrete. Begin mixing within 30
minutes after the cement has been added to the aggregates. [Place concrete
within 90 minutes of either addition of mixing water to cement and
aggregates or addition of cement to aggregates if the air temperature is
less than 29 degrees C 85 degrees F.] Reduce mixing time and place
concrete within 60 minutes if the air temperature is greater than 29
degrees C 85 degrees F except as follows: if set retarding admixture is
used and slump requirements can be met, limit for placing concrete may
remain at 90 minutes. Additional water may be added, if both the
specified maximum slump and water-cementitious material ratio are not
exceeded. When water is added, an additional 30 revolutions of the mixer
at mixing speed is required. [If time of discharge exceeds time required
by ASTM C 94, submit a request along with description of precautions to be
taken.] [If the entrained air content falls below the specified limit, add
a sufficient quantity of admixture to bring the entrained air content
within the specified limits.] Dissolve admixtures in the mixing water and
mix in the drum to uniformly distribute the admixture throughout the batch.
3.3.3
Transporting
Transport concrete from the mixer to the forms as rapidly as practicable.
Prevent segregation or loss of ingredients. Clean transporting equipment
thoroughly before each batch. Do not use aluminum pipe or chutes. Remove
concrete which has segregated in transporting and dispose of as directed.
3.4
PLACING CONCRETE
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NOTE: When necessary to deposit concrete under
water, add the following paragraph:
"Depositing Concrete Under Water
ACI 301 methods and equipment used shall prevent the
washing of the cement from the mixture, minimize the
formation of laitance, prevent the flow of water
through the concrete before it has hardened, and
minimize disturbance to the previously placed
concrete. Do not deposit concrete in running
water[, seawater,] or in water temperatures below 2
degrees C 35 degrees F. Tremies, if used, shall be
SECTION 03311
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