Page 172 - Masonry and Concrete

Masonry Construction Techniques
171
MASONRY CONSTRUCTION TECHNIQUES

through the mortar joints, and when the joints are irregular and diffi-
cult to tool, water penetration can be significant.

5.5.5 Accessories
Residential stone masonry usually is limited to veneer applications,
garden walls, and retaining walls. Steel reinforcement is seldom nec-
essary for these applications, so the accessories necessary for stone
masonry construction are usually limited to wall ties and anchors.
These need flexibility to accommodate the irregularities of the stone,
and either wire or corrugated metal are most frequently used.

5.6 Grouting Masonry

Concrete block basement walls often require steel reinforcing for
added strength. In reinforced concrete block construction, the cores of
the hollow units are pumped with grout to secure the reinforcing steel
and bond it to the masonry. All of the cores of a concrete block wall
may be grouted with reinforcement spaced every few cores, or the
grout may be limited only to the cores which contain reinforcement.
If only isolated cores of a concrete block wall will be grouted, the
cores that will be grouted must be fully bedded in mortar, including
the webs and face shell flanges. This will prevent the grout from flow-
ing beyond its intended location. If the whole wall is to be grouted, the
face shells are mortared as usual, but the webs are not. This allows the
grout to flow laterally inside the wall for better bond. Spacers are used
to maintain alignment of the vertical reinforcement to assure that grout
completely surrounds the steel for full embedment and proper struc-
tural performance. Protrusions or fins of mortar which project into the
cores will interfere with proper flow and distribution of the grout and
could prevent complete bonding.
The low-lift method of grouting a wall is done in 8-in. lifts as the
wall is laid up. Grout should be well mixed to avoid segregation of
materials, and carefully poured to avoid splashing on the top of the
units, since dried grout will prevent proper mortar bond at the suc-
ceeding bed joint. At least 15 minutes should elapse between pours to
allow the grout to achieve some degree of stiffness before the next
layer is added. If grout is poured too quickly, and the mortar joints are
fresh, hydrostatic pressure can cause the wall to bulge out of plumb. A

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