Name: _________________________________________ Date: ________________
STUDYGUIDE CHAPTER 9: CMU’S
CAREER INSTITUTE OF TECHNOLOGY
MR. BRIAN IASIELLO
TERMS:
Anchored veneer - A single-wythe masonry wall, requiring vertical support and
anchored to either a load-bearing or non-load-bearing wall, having an air space between it
and the back-up wall.
Architectural CMUs - Structural concrete masonry units whose one or more faces
are produced in a multitude of texture and color combinations, suitable for both interior
and exterior walls and foundations.
Autoclaved CMUs - Block cured in sealed steam kilns at steam pressures above 120
psi and a temperature of 350°F; it is harder and less effected by changes in weather than
block cured in steam kilns at atmospheric pressures at lower temperatures.
Exposed aggregate CMUs - Also called aggregate faced units, block having the
natural texture of crushed stone or small pebbles embedded in one or more face.
Fluted CMUs - Also called ribbed or scored block, CMUs whose one or more faces
have vertical, machine-molded grooves
Glazed CMUs - Block with a glazing compound permanently molded to one or more
faces, becoming an integral part of the unit and providing an impervious finish highly
resistant to staining, impact, and abrasion.
Ground face CMUs - Concrete masonry units with faces ground smooth and highly
polished, exposing the natural colors of the aggregates and reflecting light.
Heavyweight CMUs - Block containing primarily Portland cement, crushed
limestone, and sand.
Hollow unit - A CMU in which the cross-sectional area of the cells is more than 25%
of the overall cross-sectional area of the unit.
Lightweight CMUs - Block containing expanded shale, clay, and slate or pumice to
reduce the weight of the block and improve its performance.
Nominal size- Approximate size of CMU
Solid unit - A CMU either having no cells or the cross-sectional area of the cells are
25% or less than the overall cross-sectional area of the unit.
Sound-absorbing CMUs - Also called acoustical masonry units, structural concrete
masonry units designed to reduce sound transmission.
Split-face CMUs - Block produced by mechanically splitting multiple-molded units,
having one or more rough, exposed aggregate, three-dimensional faces.
Stone-face CMUs - Block having the natural look of hand-chiseled stone.
Structural load - The weight or pressure exerted on a structure including the weight
of the building materials, occupants, furnishings, wind, snow, and rain.
Procedures:
A. Concrete Masonry Units (CMU’s)
1. A hallow unit is one in which the cross-sectional area of the cells is more than
25% of the overall cross-sectional area of the unit.
a. Hollow spaces are called cells
2. A solid unit either has no cells or the cross-sectional area of the cells is 25%
or less than the overall cross-sectional area of the unit.
3. Heavyweight CMUs:
a. Heavyweight concrete masonry units contain Portland cement, crushed
limestone, sand and water.
4. Lightweight CMUs:
a. In addition to Portland cement, crushed limestone, sand, and water,
lightweight concrete masonry units contain expanded shale, clay , and
slate or pumice.
b. Depending on the blend of ingredients, some units are referred to as
medium-weight block since they contain both crushed limestone and
lightweight aggregates.
c. It is useful to ask the suppliers of CMUs to provide printed specifications
that include the percentages of lightweight aggregates and block weight.
B. Architectural CMUs:
1. Architectural CMUs are structural concrete masonry units suitable for both
interior and exterior walls.
2. Unlike other masonry units, architectural CMUs can be manufactured with an
integral water repellant system.
3. There are several categories of architectural CMUs.
A. Split-Face CMUs:
1. Split-face CMUs are block having one or more rough, exposed
aggregate, three-dimensional faces.
2. Split-face CMUs are created by mechanically splitting multiplemolded units. Split-face block are available in a variety of colors.
3. Split-face block are available in a variety of colors.
B. Fluted CMUs:
1. Fluted CMUs, also called ribbed or scored block, are block whose one
or more faces have vertical, machine-molded grooves, permitting the
faces of walls to exhibit continuous, three-dimensional, vertical
grooves.
2. The ribs can vary in number and can be rounded or square.
3. Fluted block are available in a variety of sizes and colors.
C. Exposed Aggregate CMUs:
1. Exposed aggregate CMUs, also called aggregate faced units, have the
natural texture of crushed stone or small pebbles embedded in the
facing of lightweight CMUs.
D. Ground Face CMUs:
1. Ground face CMUs are concrete masonry units with faces ground and
highly polished to expose the natural colors of the aggregates.
2. The surface can be finished with a coating to highlight the color.
3. The low-maintenance, sanitary finish is ideal for dairies, schools, and
laboratories.
E. Glazed CMUs:
1. Concrete masonry units with a glazing compound permanently molded
to one or more faces are called glazed CMUs.
2. The glazing compound becomes an integral part of the unit and
provides and impervious finish highly resistant to staining, impact, and
abrasion.
C. Sound-Absorbing CMUs:
1. Sound-absorbing CMUs, or acoustical masonry units, are structural concrete
masonry units having closed tops and vertical slots in front of the cavities.
2. The cells can have factory-inserted insulating fillers to reduce sound
transmission. Indoor applications include mechanical equipment rooms, noisy
plant areas, gymnasiums, and auditoriums.
3. Sound-absorbing masonry units are available either as glazed units or as
ground face units.
D. Stone-Face CMUs:
1. Stone face masonry units are concrete masonry units having the natural look
of stone.
2. They are available in a variety of colors, shapes, and sizes.
3. These attractive architectural CMUs are used either as anchored veneer or
through-wall application.
E. CMU Sizes and Dimensions:
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1. Concrete masonry units measure 15 ⁄8”long and 7 ⁄8” tall.
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2. Including ⁄8” bed and head joints, each full unit laid in the wall measures 16”
in length and 8” in height.
3. The size of a block refers to the width of the block.
4. The five standard, nominal sizes for CMUs are 4”, 6”, 8”, 10”, and 12”.
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5. The actual size or width of a CMU is ⁄8” less than the nominal sizes.
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For example: An 8” CMU is actually 7 ⁄8”wide.
6. Job specifications and local building codes determine the minimum block
size to be used.
F. Pattern Bonds:
1. CMU walls are mostly laid in the running bond pattern. This half-lap
arrangement provides the most even distribution of weight.
2. A decorative stack bond pattern is sometimes used for walls. Stack bond
pattern walls need to be reinforced with wire joint reinforcement between the
courses.
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