MIL-HDBK-1011/1
Section 3: CONCRETE
Scope. This section covers concrete materials, reinforcement,
3.1
accessories, curing, structural precast concrete, prestressed concrete, and
cast-in-place concrete.
General Design Considerations. Concrete is an ideal construction
3.2
material for permanent structures in the tropics, but like all materials, it
has advantages and disadvantages. The major problem inherent in using
concrete in the tropical region can be traced to the corrosion of embedded
steel reinforcement. This corrosion occurs when the steel is exposed to
moisture and alkaline substances. Steel must be protected from such
conditions.
3.2.1
Corrosion Protection. Take care to minimize the salt content of
both the water and aggregates (especially coral) used in the concrete mix. In
addition, protect the reinforcing steel and accessories by specified
protective coatings. Increasing the concrete cover over reinforcing steel to
protect the steel is also an important consideration in areas where salt-laden
air conditions are extreme. Such extreme conditions often exist on the
windward sides of islands in the tropics.
3.2.2
Cracking and Salt Intrusion. Cracks in hardened concrete allow
moisture and salt to come into contact with embedded steel; minimize such
cracking through careful adherence to proper construction techniques and
technologies.
3.3
Concrete Materials. The use of concrete for building components in
tropical areas is recommended provided that material availability (cement,
aggregate, and plentiful fresh water) does not make concrete construction cost
prohibitive. However, in tropical areas, because concrete components are
likely to be subjected to corrosive elements present in salty aggregates and
water, exercise special care to ensure that corrosion is limited as much as
possible.
3.3.1
Cement. Specify either Type I or Type II portland cement for
general use in tropical environments. Specify either Type II or Type V for
use in concrete structures continuously exposed to seawater.
3.3.2
Aggregates.
Where standard aggregates, such as river gravel or
manufactured aggregates, are not readily available, coral aggregates are
acceptable. The specific gravity of any coralline material shall not be less
than 2.40. Specify coral aggregates with higher specific gravity wherever
available. Wash aggregates dredged from the ocean or lagoon with fresh water
to remove as much salt as possible.
3.3.2.1
Fine Aggregates. Fine aggregate may be washed, natural beach sand,
manufactured sand, or a combination of beach and manufactured sand.
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