MIL-HDBK-1011/1
Section 4: MASONRY
4.1
Scope. This section pertains to concrete masonry units (CMU), both
solid and hollow, used in general construction. Clay bricks are not included
since their use in many areas cannot be economically justified.
4.2
General Design Considerations
4.2.1
Water Infiltration. Water infiltration of concrete masonry units
is the major problem associated with the use of masonry in the tropics. Give
careful attention to the density of the block as well as to the tooling of
joints, and applications employed to reduce water infiltration. As with
concrete, avoid salt in the aggregate or water. Limit chloride concentration
in the mortar mix to minimize corrosion of embedded steel items.
4.2.2
Block Selection. Avoid the use of split-face and scored-face units
in outdoor or exposed applications. These units are difficult to properly
seal with block filler during painting and ultimately may contribute to leaks
or moisture problems. Additionally, scored-face units may accumulate dirt and
provide a place for wind-born seed germination. Consider these units a
maintenance problem because of the difficulty of cleaning them.
4.3
Construction/Materials Consideration. CMU is very often the
material of choice in the tropical regions because of its universal
availability and the familiarity of local workmen with its use. Because of
the scarcity of clean water and aggregate in many areas of the tropics, it is
frequently the only choice. It is ideally suited for use in low-rise and non-
air conditioned structures.
4.4
Masonry Units
4.4.1
Application.
Concrete masonry units are acceptable for general
construction in the tropical environment. A major disadvantage for their use
for exterior wall construction is high porosity. The wind-driven rain in the
tropics can readily infiltrate the units and create moisture problems if
appropriate action to prevent water infiltration of the masonry units is not
taken. Although some success has been achieved in stopping water infiltration
through masonry units, it has been on a short term basis and periodic surface
treatment is necessary to ensure continued protection. CMU construction can
be extensively used in the tropics; however, quality control must be ensured.
Tool all joints exposed to the weather to ensure maximum compaction and
density of the joint mortar. Do not specify struck joints except for interior
surfaces of walls or where water infiltration will create no problems.
4.4.2
Materials.
Do not use brackish water or seawater in any connection
with masonry construction. Specify Type I or Type II portland cement for the
manufacture of the masonry units and for the mortar and grout.
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