TM 5-822-7/AFM 88-6, Chap. 8
the contract specifications. The mixture proportions
the Government, and the results will be submitted
determined by mixture proportioning studies will be
to the contracting officer for approval. When the
contracting officer is responsible for mixture
used in starting paving operations. Adjustments
will be made by the contractor as necessary to
proportioning, trial mixtures will be prepared by the
establish the mixture proportions best suited for the
Government with materials supplied by the contractor
from the sources to be used for production of concrete
job conditions and materials used. Project specifi-
cations will require the contractor to notify the
on the project. Mixtures will be made in sufficient
number to establish optimum proportions of the
contracting officer prior to making any change to
the approved mixture proportions and to indicate
aggregates and to represent a wide range in cement
the changes to be made. Changes to the mixture
contents and watercement ratios within specified
proportions will be of a minor nature as required to
requirements for air content and workability. The
water-cement ratio will not exceed 0.45 by weight
compensate for variations in gradings and the
moisture content of the aggregate unless laboratory
for pavement mixtures. After the final proportions
mixture studies for the new mixture are submitted
of the trial mixtures have been established, 6inch
for approval.
by 6-inch cross-section test/beam specimens from
c. Workability. The concrete slump shall not exceed
each mixture will be made in accordance with
ASTM C 192 and tested as described in ASTM C 78.
2 inches. Within this maximum limit, the slump will
A minimum of nine test specimens should be made
be maintained at the lowest practical value suitable
to establish the flexural strength of each mixture at
for prevailing weather conditions and for equipment
each test age. From these mixture proportioning
and methods used in placement of the concrete. For
studies, the controlling maximum water-cement
small paved areas, slump in excess of 2 inches may
ratio and hence the cement content required to
be permitted, but in no case will the slump exceed 3
inches. The concrete slump will be determined in the
produce concrete of specified strength will be deter-
field by the method described in ASTM C 143. Slump
mined. This same procedure will be used to establish
new mixture proportions when necessary because of
for slipform paving of airfield and heliport pavements
a change in the source or the character of the concrete
should be specified in a range of O to 1 inches.
ingredients after concrete placement has started.
d. Strength. Control of the strength of the concrete
b. Mixture proportions.
mixture will be based on tests of concrete specimens
(l.) Contracting officer responsible for mixture
taken during the paving operations. Pavements to
proportions. When the contracting officer is respon-
be used by aircraft are designed on the basis of the
sible for the mixture proportions, proportions of all
flexural strength that the concrete is expected to
materials used in the concrete mixture will be as
attain at 90 days, and specimens will be tested at
directed. The contracting officer will require such
this age for use in the evaluation pavements. Since
changes in the mixture proportions as necessary to
the period necessary to obtain the 90-day field
maintain the workability, strength, and quality
strengths is too great to exercise proper control of
required by the contract specifications. The mixture
the concrete during pavement construction, a 14-day
proportions determined by mixture proportioning
strength requirement will be included in the contract
studies will be used in starting paving operations.
specifications. Flexural-strength tests will be made
Adjustments will be made by the contracting officer
at 14 days to determine compliance with the 14-day
as necessary to establish the mixture proportions
strength requirement. In addition, 7-day strength
best suited for job conditions and materials used.
tests will be made to provide an early indication of
Subsequent mixture adjustments will be made when
the concrete strength. The average strength at the
necessary, but usually these adjustments will be of a
age of 14 days of any five consecutive individual test
minor nature as required to compensate for variations
values representing each concrete mixture will be
in gradings and the moisture content of the aggregate.
not less than the specified strength at the age of 14
(2.) Contractor responsible for mixture propor-
days, and not more than 20 percent of the individual
tions. When the contractor is responsible for the
values will be less than the specified strength.
mixture proportions, proportions of all materials used
Adjustments of the concrete mixture proportions
in the concrete mixture will be as directed by the
will be made as necessary to maintain this strength
contractor. The contractor will require such changes
control. When sufficient 90-day strengths become
in the mixture proportions as necessary to maintain
available, further adjustment of the concrete mixture
the workability, strength, and quality required by
may be made as necessary to assure that the 90-day
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