TM 5-822-7/AFM 88-6, Chap. 8
can be specified. Grading and uniformity of grading
tests if the results show no change in the composition
requirements will be determined as the aggregates
and quality of aggregate. For proper design and
preparation of plans and specifications, it is
are delivered to the mixer, and the contractor is
responsible for meeting these requirements. Careful
necessary to investigate and determine suitable
inspection of storage and handling operations,
aggregate sources and concrete strengths obtainable
however, is desirable to assure satisfactory control
with aggregates. It is essential that these investiga-
of the aggregate grading and to prevent contamin-
tions be conducted as early as possible during project
ation by foreign material. Aggregate storage tech-
planning.
niques that use coned piles or spread truck-dumped
(2.) Sources for calibration hardstands. When
aggregate with a bulldozer cause segregation
contract specifications cover the paving of calibration
problems. Aggregates delivered by trucks are best
hardstands, the list of sources will indicate which
dumped and left in individual adjacent piles. A clam
sources are approved for such work.
shell spreading aggregate in thin layers has also
(3.) Aggregate sources not previously listed.
been used to minimize segregation. Aggregate
When the contractor proposes aggregate from a
source not previously listed, the evaluation of
should be handled as little as possible to minimize
segregation. Potential sources of contaminants
samples of that aggregate will include all tests
necessary to demonstrate that a concrete produced
include windblown foundation and adjacent
from the materials will have quality and strength
materials and contaminants from equipment used in
handling the aggregates.
comparable with that of concrete made with aggre-
(2.) Moisture control. Uniformity of free
gate from the approved sources listed. When the
moisture in aggregate is essential for proper control
contracting officer is responsible for mixture
proportioning and cement is a separate pay item in
of concrete consistency. A period of free-draining
the contract, aggregates of good quality that require
storage is required for fine aggregates and the
an increase in the quantity of cement over that
smaller size of coarse aggregate. Normally, 24 to 48
hours will be sufficient. However, shorter or longer
required by aggregates from listed sources to produce
times may be specified if the tests of time to reach
concrete of the specified flexural strength will be
an equilibrium so indicate.
approved for use only if the contractor agrees in
writing to pay for the additional cement required.
12. Grade control. The lines and grades shown for
(4.) Unlisted source. When the contract
each airfield and heliport pavement category of the
specifications do not include a list of approved
contract shall be established and maintained by
aggregate sources, the source(s) proposed by the
means of line and grade stakes placed at the jobsite
contractor will be investigated as soon as possible
by the contractor. Elevations of all benchmarks used
after the award of the contract.
by the contractor for controlling pavement operations
(5.) Aggregates for a small project. Evaluation
at the jobsite will be established and maintained by
of aggregates from non-listed sources and concrete
the Government. The finished pavement grade lines
mixture proportioning for projects requiring 1,600
and elevations shown shall be established and
cubic yards or less of concrete, except for airfield
controlled at the jobsite in accordance with bench-
and heliport paving, will be performed by an approved
mark elevations furnished by the contracting officer.
commercial testing laboratory at no expense to the
The pavements shall be constructed to the thicknesses
Government.
and elevations indicated. Provisions for line and
grade control for roads, streets, and open storage
11. Delivery and storage of materials.
areas shall be included in the contract specifications.
a. Cement and pozzolan. Separate storage facilities
will be provided for each type of cementitious
13. Proportioning.
material. Storage facility will be thoroughly cleaned
a. Mixture proportioning. Before any concrete is
before changing the type of cementitious material
stored init. Storage facilities must be weather-tight
placed, trial mixtures will be prepared with
materials from the sources to be used for production
and must be properly ventilated.
b. Aggregates.
of concrete on the project. When the contractor is
responsible for mixture proportioning, trial mixtures
(l.) Control of grading. Aggregate-handling and
will be prepared by a commercial testing laboratory
aggregate-storage facilities may vary greatly for
different projects, and only general requirements
approved by the contracting officer at no expense to
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