Retrofit of Walls
1) Concrete Wall
Retrofit. Sand in combination with
predetonation screens can be used
in sandbags or in sand-grid
retrofit concrete walls.
Sand-grids (see Figure 74) are more
easily transported and require less
construction time than sandbags.
The expanded configuration shown in
Figure 74 is placed in a vertical
configuration and filled with sand.
The required thickness of sand for
concrete and a predetonation screen
at various standoffs is summarized
in Figure 75. A spall plate
consisting of 0.5 inch (12.5 mm) of
polyethylene is also employed
on the interior wall. This plate
reduces the concrete thickness
required to stop the RPG from
penetrating. Choices of standoff
distance, sand depth, and wall thickness will vary with user
requirements. Figure 75 allows the user to determine the combinations that
best fit his needs.
2) CMU Wall Retrofit. Sand can also be used with CMU to
reduce the jet penetration of an RPG. For example, test results for 12-inch
(300-mm)- thick CMU require 32 inches (812 mm) of sand on the exterior with
0.5 inch (12.5 mm) of polyethylene on the inside (as a spall plate) to
successfully stop the jet. Presently, there is no test data for other CMU
3) Other Materials. Other materials such as wood cannot
effectively be retrofit-hardened against an RPG attack.
Retrofit of Roof and Floors. Because of the large quantities of
material required to stop an RPG jet, structural considerations preclude
their application to roofs or floors open from above or below. Critical
assets can only be protected from above and below using sacrificial areas as
discussed in par. 220.127.116.11.
Areas to be protected against an RPG attack should be
free of windows.