CEE 395- Materials for Constructed Facilities
Civil Engineering Materials
Masonry Units
Week 15, Lecture 26
Introduction
 A masonry structure is formed by combining masonry
units such as stone or brick with mortar
 Extensive use of masonry in the U.S. started in the
1600's
 Masonry can be used for sewers, bridge piers, tunnel
linings, and multistory buildings
Masonry Units
Can be classified as:
1. Concrete masonry units
1.1. solid or
1.2. hollow
2. Clay bricks:
2.1. typically solid
2.2. Structural clay tiles: hollow
3. Glass blocks: solid
4. Stone: solid
Concrete Masonry Units
Manufacturing
 Made with zero slump PCC
 Units molded under pressure
 Cured under controlled conditions with steam curing
 Usually made from type I Portland Cement, but Type
III has been used to reduce curing time
 Air entrainment is added to improve workability,
compaction, molding, and freeze and thaw effects
Classifications of Concrete Units:
 Hollow or solid
 Bearing or Non-bearing
 Light, Medium, or normal-weight
1. Based on ratio of the net X-sectional area to the total
area
- Hollow Units: < 75%
- Also known as concrete blocks, hollow blocks, or
cinder blocks
- Solid Units: > 75%
- Also known as concrete bricks
2. Based on weight (Table 8.1)
- Normal-weight
- > 2.00 Mg/cu.m, 125 pcf
Made from well-graded sand, gravel & crushed stone
- Medium-weight
1.68 Mg/cu.m to 2.00 Mg/cu.m, ranges from 105 pcf
to 125 pcf
Notes:
Masonry Units
Week 15, Lecture 26
- Light-weight
< 1.68 Mg/cu.m, 105 pcf
Made from lightweight aggregates such as purnic,
scoria, cinders, expanded clay, and expanded shale
Used because of ease of handle and transport, reduced
weight of structure, higher thermal and fire resistance
Disadvantage - lower sound resistance
3. Based on strength (Table 8.2)
- Load Bearing
Minimum strength requirement of 11.7 MPa (1700
psi) for one unit, 13.1 MPa (1900 psi) for 3 unit
average
- Non-Load Bearing
Minimum strength requirement of 3.5 MPa (500 psi)
for one unit, 4.1 MPa (600 psi) for 3 unit average
Testing: Performed by capping the unit and applying the load
in the direction of the height until failure (ASTM C140). Test
can be performed on full-size unit or a portion of the unit if the
testing machine is not large enough.
- The gross area compressive strength
The load at failure divided by gross cross-sectional area
- The net area compressive strength
The load at failure divided by the net cross-sectional area
Sub classification of load-bearing units (ASTM C90)
1. Type I, moisture-controlled units
- Limit the amount of shrinkage due to moisture loss
- Used in arid regions
- Must be protected from moisture before being used or
dry shrinkage will occur
2. Type II, non-moisture controlled units
- No moisture control required
- Used in humid regions
- Stored until climatic balance in units is met
- More commonly used than type I
Calculation of absorption and moisture content
Performed by immersing the unit in water for 24 hours
(ASTM C140)
Absorption (%) = (Ws - Wd)/Wd (100) (Equation 8.1. in text)
Moisture content as a percent of total absorption
(Wr - Wd)/(Ws - Wd) (100) (Equation 8.2. in text)
Where:
Ws = saturated weight of the unit
Wd = oven-dry weight of the unit
Wr = weight of unit as received
(Con’t)
Notes:
Masonry Units
Week 15, Lecture 26
Grades and Shapes of Concrete Masonry Units
 Available in different sizes, colors, shapes, and textures
 Nominal dimension is greater than the specified or
modular dimension because it includes the thickness of
a 3/8 inch mortar joints
For example:
An 8 inch X 8 inch X 16 inch block has an actually
measures 7-5/8 inch X 7-5/8 inch X 15-5/8 inch
 Load-bearing units. Available in
- Widths of 4, 5, 8, 10, 12"
- Heights of 4" and 8"
- Lengths of 12, 16, and 24"
 Common bearing units are 8" X 8" X 16" whereas
common non-load bearing units are 4" X 8" X 16"
Shapes of Concrete Masonry units (Figure 8.4)
1. Stretcher
2. Single-Corner
3. Double-Corner
Grades of solid concrete masonry units
Grade N:
- Higher compressive strength
- Resistant to moisture penetration
- Resistant to frost penetration
- Minimum compressive strength of 3000 psi
- Used as architectural veneering / exterior facing units
Grade S:
- Minimum compressive strength of 13.7 MPa (2000 psi)
- Used where moderate strength and resistance to frost is
required
Clay Bricks
 Small, rectangular blocks made of fired clay
 Clays are composed mainly of silica (grains of sand),
alumina, lime, iron, manganese, sulfur, and phosphates,
with different proportions
 Clays can vary widely in composition
 Average density of 2 Mg/cu.m (125 pcf)
Manufacturing of Clay Bricks
 Grinding or crushing the clay in mills and mixing it
with water to make it plastic
 Plastic clay is molded, textured, dried, and finally dried
 Firing temperature varies from 900 C to 1200 C (1650
F to 2200 F)
Various Colors
 Dark red, purple, brown, gray, pink, or dull brown
 Depending on the firing temperature of the clay during
manufacturing
(Con’t)
Notes:
Masonry Units
Week 15, Lecture 26
Utilities of Clay Bricks
1. Building bricks (common bricks)
Used as a structural material and typically are strong
and durable
2. Facing bricks
Used for facing and aesthetic purposes and are available
in different sizes, colors, and textures
3. Floor bricks
Used on finished floor surfaces and are generally
smooth and dense and have high resistance to abrasion
4. Paving bricks
- Used as a paving material for roads, sidewalks, patios,
driveways, and interior floors
- Available in different colors: red, gray, or brown
- Abrasion resistant and could be vitrified
Advantages of using Clay Bricks
 Very durable
 Fire-resistant
 Require very little maintenance
 Moderate insulating properties: makes brick houses
cooler in summer and winter, as compared to houses
built with other construction materials
 Non-combustible and poor conductors
Absorption
 One of the important properties that determine the
durability
 Highly absorptive bricks can cause efflorescence and
other problems in the masonry
 ASTM C67 define the absorption by 24 hour
submersion, absorption by 5 hour boiling, and
saturation coefficient as follows
Figure 8.3, Figure 8.4, Figure 8.5
where:
Wd = dry weight of specimen
Ws24 = saturated weight after 24 hour submersion in cold
water
Wb5 = saturated weight after 5 hour submersion in boiling
water
(Con’t)
Notes:
Masonry Units
Week 15, Lecture 26
Compressive Strength of Clay Bricks
 Controls their load-carrying capacity and durability
 Dependent on
1. composition of the clay
2. method of brick manufacturing
3. the degree of firing
 Determined by capping and testing a half unit
"flatwise" (load applied in the direction of the height
the unit). Calculated by the cross sectional area (ASTM
C67)
1. Either the net or gross cross-sectional area is used
2. Only use net cross-sectional area if the net crosssectional that 75% of the gross cross section
3. A quarter of a brick can be tested if the capacity of
the testing machine is not large enough to test a half
brick
Other mechanical properties of bricks
1. Modulus of Rupture
Between 3.5 MPa and 26.2 MPa (500 psi and 3800 psi)
2. Tensile Strength
Between 30% to 49% of the modulus of rupture
3. Modulus of Elasticity
Between 10.3 GPa and 34.5 GPa (1,5.10^6 psi and
5.10^6 psi)
Grading of Building Bricks
 Graded according to properties related to durability and
resistance to weathering
i.e. compressive strength, water absorption, and
saturation coefficient (ASTM C62)
 3 available grades and requirements (Table 8.3 in text)
1. SW: Severe Weathering
Intended to use in areas subjected to frost action,
especially at or below ground level
2. NW: Negligible Weathering
For areas with no frost and in dry locations, even where
sub-freezing temperatures are expected. Can be used in
interior construction, where no freezing occurs
3. MW: Moderate Weathering
Grading of Facing Bricks (ASTM C216)
 Two durability grades
Severe weathering (SW) and Moderate weathering (MW)
 Each durability grade is made in 3 appearance types:
1. FBS: Face Brick Standard
Used for general exposed masonry construction
2. FBX: Face Brick Extra
Used for general exterior and interior masonry
construction where a high degree of precision and
low variation is size are required
3. FBA: Face Brick Architecture
Used to produce characteristic architectural effects
resulting from non-uniformity in size and texture of
the individual units
(Con’t)
Notes:
Masonry Units
Week 15, Lecture 26
Nominal Dimension of the brick
 Its specified dimension by thickness of the mortar joint
(10 mm and go up to 12.5 mm)
 Actual size depends on the nominal size and the amount
of shrinking that occurs during the firing process, which
ranges from 4% to 15%
 Specification of clay bricks
 4 X 2-2/3 X 8 brick (nominal width X height X length)
 Nominal widths: 3 inch to 12 inch
 Nominal heights: 2 inch to 8 inch
 Nominal lengths: up to 14 inch
 Bricks can be classified as either modular or nonmodular where modular bricks have widths and lengths
of multiples of 4 inch (100 mm)
(Con’t)
Notes: