Masonry Magazine August 1995 Page. 21
Sash unit
All purpose or kerf unit
Control joint unit
Bull-nosed unit
Screen units
Bevelled unit
Figure 4-Special Shapes
Figure 5 Concrete Masonry Units Designed For
Maximum Energy Efficiency
Figure 6-Examples of Acoustical
Concrete Masonry Units
easily split on the jobsite, producing two 8 in. (203 mm) long units, which are typically used adjacent to openings or at the ends or corner of a wall. Bull-nosed units are available with either a single or double bull nose, to soften corners. Screen units are available in many sizes and patterns. Typical applications include exterior fences, interior partitions, and openings within interior concrete masonry walls. Bevelled-end units, forming a 45° angle with the face of the unit, are used to form walls intersecting at 135° angles. Units in adjacent courses overlap to form a running bond pattern at the corner.
A variety of concrete masonry units are designed to increase energy efficiency. These units, examples of which are shown in Figure 5, may have reduced web areas to reduce heat loss through the webs. Web areas can be reduced by reducing the web height or thickness, reducing the number of webs, or both. In addition, the interior face shell of the unit can be made thicker than a typical face shell for increased thermal storage, and hence further increase energy efficiency. Insulating inserts can also be incorporated into standard concrete masonry units to increase energy efficiency.
Acoustical units (Figure 6) dampen sound, thus improving the noise reduction attributes of an interior space. Acoustical units are often used in schools, industrial plants, and churches, and to improve internal acoustics.
SURFACE FINISHES
The finished appearance of a concrete masonry wall can be varied with the size of units, shape of units, color of units and mortar, bond pattern, and surface finish of the units. The various shapes and sizes of concrete masonry units described above are often available in a choice of surface finishes. Some of the surfaces are molded into the units during the manufacturing process, while others are applied separately.
Figure 7 shows some of the more common surface textures available. Ribs, flutes, striations, offsets, and scores are accomplished by using a unit mold with the desired characteristics. Split-faced units are molded with two units face-to-face. Then the units are mechanically split apart after being removed from the mold, leaving the split face with a rough texture similar to natural stone. As Figure 7 shows, split-faced units can be manufactured with or without ribs or scores. For split-faced units, ASTM C 90 allows up to 10% of the split face shell area to have a thickness less than the minimums listed in Table 1, but not less than 4 in. (19 mm).
Glazed units are manufactured by bonding a permanent colored facing to a concrete masonry unit, providing a smooth impervious surface. Glazed units are often used for brightly-colored accent bands, and in gymnasiums, rest rooms, and indoor swimming pools where the stain and moisture resistant finish reduces maintenance. Glazed units comply to Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units, ASTM C 744 (ref. 5).
Ground-face units are ground to achieve a smooth finish which reveals the natural colors of the aggregates. The finished look of the polished surface is determined by aggregate type and proportions as well as any color used in the concrete mix. Often, specific aggregates will be used to enhance the appearance of the polished surface.