Masonry Flashcards
Mortar
mixture of cement, lime, sand, and water
- normally portland cement is used
- lime is a plasticizer; helps retain water improving workability
Made of portland cement, hydrated lime, an inert aggregate (sand), and water
• Sand must be clean and screened to get out particles that are too coarse or fine
• Portland cement is “harsh” meaning that it doesn’t flow well on a trowel or under a
brick….lime is added to impart smoothness and workability
• Lime is made by burning limestone or seashells in a kiln to drive of CO2 and leave
quicklime, which is then allowed to absorb as much water as it will hold. This is
called hydrated lime. It’s dried, ground, and bagged for shipping
Makes up about 20% of the exposed surface of a brick wall
• Serves to cushion the masonry units and allow them to bear fully against one another
despite surface irregularity
• Seals between the units to keep water and wind from penetrating
• Adheres units to one another to bond them into a monolithic structural unit
• Portland cement mortar cures by hydration, not by drying. A set of chemical reactions
take up water and combine it with the cement and lime to create a dense, strong
crystalline structure that binds sand particles and masonry units together
• If mortar is mixed less than 90 minutes prior to its stiffening it has only dried and a
mason can safely retemper it with water to make it workable again (note, this is not
the case with concrete!)
• Mortar older than 2 1/2 hours must be discarded because it has begun to hydrate and
can’t be retempered without reducing its final strength
masonry cement
prepared mixture of portalnd cement and pulverized limestone
- not as strong of expensive as portland cement, but has greater plasticity
- suitable for lowrise building veneers and for interior, non loadbearing applications
mortar types
Types M or S: for masonry that is load-bearing and/or exposed to the weather.
• Types N and O: lesser compressive strength required.
- each has a different porportion of cement, lime, and aggregate
- each has a different compressive strength
grout
similar to mortar
- used to fill cavities between masonry units
- fine grout is used when dimensions of cavity is less than 2 in
- course grout includes no 4 aggregate
• Grades for Building and Facing Bricks
• Grade SW: Sever Weathering (Oregon, most of the Eastern half of US)
- Grade MW: Moderate weathering (Midwest, most of Washington)
- Grade NW: Negligible weathering (Along southern US border)
• ASTM testing procedures establish three grades of brick based on resistance to weathering and three types of facing bricks, bricks that will be exposed to view, based on the degree of uniformity in shape, dimension, texture, and color from one brick to the next
brick masonry
Produced by factories all over the place with local clay and shale. It’s expensive to
ship long distances because it’s so heavy.
- After molding bricks are dried for 1-2 day sin a low temp dryer kiln and then fired
- Entire process of firing takes about 40 - 150 hours
- There’s no truly standard brick size. The most common is 8” x 3 5/8” x 2 1/4”
- Use of larger bricks can lead to substantial economies in construction
- Brick shapes can be solid, cored, hollow, or frogged
- Reducing the volume of a brick reduces fabrication, transportation costs
molding method for brick
- Molding methods:
- Soft mud process: (oldest method) relatively moist clay is pressed into simple rectangular molds
- Dry-press process: use for clays that shrink excessively during drying, clay mixed with water is pressed into steel molds by a machine working at high pressure
• Stiff mud process: high-production, most widely used, clay with water is extruded and sliced by wires to form brick
Types of Facing Bricks
available in SW and MW grades
• Type FBX: High degree of perfection, narrow color range, slight size variation
- Type FBS: Wide range of color and greater size variation per unit
- Type FBA: Non uniformity in size, color, and texture per unit
• Needle Beam:
a temporary member thrust under a building or foundation used in underpinning
Hallow brick
available in SW and MW grades
-classified according to appearance
HBS: general use where range of size and color variation are acceptable or desired
HBX: used when a high degree of mechanical perfections, narrow color range, and minimum variation in size is required
HBA: non uniform in color, size, and texture
Wythe:
simplest wall, a vertical layer of masonry units one unit thick
Course:
a horizontal layer of bricks or other masonry units
Stretcher:
a brick laid with its face parallel to the wall and its long dimensions
horizontal
Header:
a brick laid to bond two wythes together
Solider:
brick laid on its end with its face (long skinny side) parallel to the wall
Sailor:
brick laid on its side with its end parallel to the wall
Rowlock:
brick laid on its face with its end (short skinny side) visible in the wall.
Often used for caps on walls and floor sloping sills under windows
Name Brick laying positions
name common mortar joints
Expansion joints are required when structure is over
200’ long or where wings occur
- Major expansion joints are spaced every 100 ft to 150 ft in large buildings
- expansion and control joitns are spaced every 20 ft and at places where the wall changes direction, height, or thickness
- horizontal expansion joints should be placed below shelf angles that support intermediate sections of brick and below beams and slabs above brick
Joints in brickwork are tooled ___hours after laying as the mortar begins to harden,
1-2
-joints must be appropriate for the weather condition the wall is located in.
the slope of brick coping at top of a masonry wall is called
the wash
Efflorescence
• Sometimes appears on the surface of a wall of brick, stone, or concrete masonry
• Consist of one or more water soluble salts that were originally present in the
masonry unit or in the mortar
• Brought to the surface and deposited there by water that seeped into the masonry,
dissolved the salts, then migrated to the surface and evaporated
• Can be avoided by choosing masonry units that are lab tested and don’t contain
water soluble salts
• Will eventually diminish and disappear with time as the salt is gradually leached
out of the wall
Abutment/Construction/Isolation Joints:
placed at junctions between masonry
and other materials, or between old and new masonry, to accommodate
differences in movement.
tuck pointing or repointing
- method of restoring mortar in masonry walls
- mortar in areas to be redone is removed to about 2.5 times the depth of the joint
- joint is then cleaned and wetted with water
- new mortar is pressed into the joint with a special tuck pointing tool
- high lime mortar is best and should be applied in layers
Concrete Masonry Units (CMU’s)
• Stiff concrete mixture is placed in steel molds, cured, and quickly dried. • Includes concrete brick, concrete block, concrete tile, and cast stones
• Typical concrete block size is 7 5/8” x 7 5/8” x 15 5/8”
• Many colors and surfaces types are available
• Hollow concrete block masonry is generally more economical per unit of wall area
than brick or stone masonry.
• Blocks are cheaper on a per unit basis and made into a wall more quickly
because of their size
• Widely used in masonry bearing wall construction due to strength and insertion of
rebar and grout into cores
• Often used as a backup wythe behind brick or stone facing, or stucco, plaster, tile
• Single wythe exterior concrete masonry walls tend to leak in wind driven rains
• Exterior should be painted with masonry paint
• Walls subject to moderate stresses can be reinforced horizontally with steel joint
referencing which is thin enough to fit into an ordinary bed joint of mortar
• Vertical reinforcing is done with ordinary reinforcing bars grouted into the cores
of the blocks
• Lintels for concrete block are comparable to those of brick masonry:
• Steel lintel: wide flanged section welded to a plate
• Reinforced block lintel: made of bond beam units filled with grout and rebar • Precast reinforced concrete block lintel: totally visible
• Decorative CMUs
• Easily made in a variety of surface patterns, textures, colors, interior/exterior
applications
• Include scored face, ribbed face, fluted face, angular face, etc.
concrete blocks are considered solid when
it has 75% or more solid material in any general cross section, otherwise it is considered hallow
CMU dimension are based on…
nominal 4 in module
- actual dimensions being 3/8 in less than the nominal dimension
- unit dimension are referrede to by width, height, and then length
What is the equivalent thickness of an 8 in thick concrete block that is 60 % solids
- equivalent thickness is the solid thickness that would be obtained if the same amount of concrete contained in a hallow unit were recast without core holes
- actual thickness = 7 5/8 in (7.625 in)
equivalent thickness then = (7.625)(.60)=
4.58 in
Structural Clay Tile:
hollow burned clay masonry units, architectural terra cotta is clay tile in various colors
2 grades of glazed structural tile: S-used with relatively narrow mortar joints; SS-used where the variation of face dimensions must be very small
two types: side construction and end construction
Stone is classified by…
the way it is shaped and prepared prior to installation
rubble: stone used with little or no shaping
squared stone: stone with slightly shaped edges resulting in vertical joints
ashlar: highly shaped, thick pieces of stone
Stone Masonry
• Building stone is obtained by taking rock from the earth and reducing it to the require shapes and sizes for construction
• Igneous rock: rock that was deposited in a molten state (granite, basalt)
• Sedimentary rock: deposited by the action of water and wind (limestone,
sandstone, brownstone)
• Metamorphic rock: formerly either igneous or sedimentary rock transformed by
heat or pressure (marble, soapstone, slate)
• Stone blocks are often used as exterior facing with a concrete masonry backup wall
• Stonework must stay clean, flashings must be plastic or nonstaining metal, work is
kept covered as much as possible
• Stonework can only be cleaned with mild soap, water, and a soft brush
• Stone is used in two fundamentally different ways in buildings:
- Laid in portland cement mortar like bricks or concrete blocks. Avoid moisture penetration
- Mechanically attached in large sheets to the structural frame and walls as thin facing (less common)
• Types of stone classification:
- Rubble: unsquared pieces of stone
- Ashlar: squared pieces of stone
- Coursed: continuous horizontal joint lines • Uncoursed/Random: no horizontal lines
brick weathing in the USA
common or american
english
enlgish cross or dutch
flemish
running bond
stack
Calculate the skewback for the jack arch shown. the wall is two wythes thick
answer: 9 inches
skewback is the horizontal distance from the upper corner of the masonry opening to the opper outside corner of the jack arch.
-it is equivalent to 1/2 in per foot of span for each 4 in of span depth
skewback = (span/24)(arch depth/4 in )
