Page 337 - Masonry and Concrete

Masonry Garden Walls

336 CHAPTER NINE

plaster, you cannot retemper the mix with
STANDARD 2-CORE water as usual because it will dilute the
OR 3-CORE UNITS
LAID ON EDGE colors, so mix smaller batches that you
can use up before the mix water begins to
evaporate.

9.5 CMU Screen Walls

Concrete block screen walls can be built
using either decorative screen blocks or
regular two-core or three-core utility
SPECIAL SCREEN
blocks turned on edge (Figure 9-25). CMU
BLOCK
screen walls are usually built with sup-
porting pilasters for added strength. Rec-
ommended pilaster spacing is based on
height-to-thickness ratio and is the same
as for brick walls (see Figure 9-3). One of
the simplest ways to build CMU pilasters
is to use special pilaster blocks with
notches into which the screen block can be
FIGURE 9-25 nested, and a center core for reinforcing
steel (Figure 9-26). At the pilasters, the
CMU screen block and wall bonding patterns.
concrete footing should be widened to
accommodate the extra wall thickness. For
a nominal 18-in. 16-in. pilaster in an 8-in.-wall, widen the 16-in.
wide footing to 36 in. 32 in. (see Figure 9-2). No. 3 steel reinforcing
bars in the footing should turn up 18 in. (Figure 9-27) and overlap the
vertical steel bars in the pilaster at least 12 in. (Figure 9-28). The lap
splice should be tied tightly with steel wire, and the steel in the
pilaster must be held upright until it is embedded in grout. Build the
pilaster up four courses at a time, and allow the mortar and units to
cure overnight. Then grout the cavity solidly with a mortar mix to
3
which extra water has been added. Stop each grout pour about 4 in.
below the top of the block. This will form a “key” with the next pour
and make the pilaster stronger (Figure 9-29). Use an extra rebar to stir
or agitate the grout slightly to make sure that all the corners and
recesses are filled and that there are no pockets of trapped air. Let
these first courses of the pilasters cure for a few days before building
them higher.

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