Masonry
History
• Oldest Brickwork 7500BC
• Romans first to Kiln Fire
• Become a Staple of the Building Industry after
Great London Fire
Types
• Clay
• Concrete
• Calcium
Clay Bricks
• Hand Made
• Dry Pressed Brick
• Extruded Bricks
Hand Made
• Bricks Formed into shape
• Fired at 1200°C
• Expensive
• Sizes Vary
• Very Soft – will not take mechanical anchors
• Older areas of Sydney
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its Contributors or Licensed Partners and are being used with permission under license.
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Note – Clay is not
Compressed
Certain images and/or photos on this page are the copyrighted property of 123RF Limited,
its Contributors or Licensed Partners and are being used with permission under license.
These images and/or photos may not be copied or downloaded without permission from 123RF Limited
.
Certain images and/or photos on this page are the copyrighted property of 123RF Limited,
its Contributors or Licensed Partners and are being used with permission under license.
These images and/or photos may not be copied or downloaded without permission from 123RF Limited
.
Voids due to
Lack of Compaction
Distortion due to
no compaction
Shrinkage due to
no compaction
Edges not properly
formed
Dry Pressed Bricks
• Clay pressed in Moulds
• Moulds pressed under pressure
• Bricks are moderately hard
• Can accept mechanical fixings
• Can accept nails from explosive power tools
Edges well formed & Sharp
Face has Cork like
Appearance
As Bricks are pressed into moulds bricks are a consistent size
Care must be taken as Bricks chip easily.
• Reduce Movements
• Plan Access
May be damaged by cleaning process
May be damaged by cleaning process
Extruded Bricks
• forcing a continuous slab of clay through a
mould (“Extruded Bricks”)
Extruded Bricks
• forcing a continuous slab of clay through a
mould
• Bricks the cut with wire to size
(Also known as “Wire Cut”)
Insert Photo
• Bricks being cut with wire
Extruded Bricks
• forcing a continuous slab of clay through a
mould
• Bricks the cut with wire to size
(Also known as “Wire Cut”)
• Face Textures by Rollers
Holes in Bricks
• These are extruded bricks and the holes are
called core holes or perforations that allow
the brick to be fired more evenly.
• The Australian Standard states that core holes
of up to 30 % of the material thickness have
no effect on the insulation or fire resistance
value of the brick.
Calcium Silicate
• The raw materials for calcium silicate bricks include
lime mixed with quartz, crushed flint or crushed
siliceous rock together with mineral colourants. The
materials are mixed and left until the lime is
completely hydrated, the mixture is then pressed into
moulds and cured in an autoclave for two or three
hours to speed the chemical hardening. The finished
bricks are very accurate and uniform, although the
sharp arrises need careful handling to avoid damage to
brick (and bricklayer). The bricks can be made in a
variety of colours, white is common but pastel shades
can be achieved.
Holes in Bricks
• Holes Reduce Weight
• Holes allow the mortar to bind
Bricks - Types
Durability
• Building Code of Australia (BCA) states that
masonry units must be classified and used in
the exposure conditions appropriate to their
classification
Durability
• Australian Standard AS 3700 (Masonry
Structures) provides details of these
classifications
Durability
• Brick is permanent. Once it's built it remains weatherproof
and age proof. Brick doesn't get tired like man-made
materials, so it requires virtually no upkeep or repairs.
Bricks don't rust or erode, rot or decay, bend, twist or warp.
Brick is a great protector - against the extremes of the
Australian climate - heat and cold.
• Australia is a country of extremes. At any one time,
different parts of our continent can be experiencing
bushfires, floods, severe storms and drought. And climate
change researchers suggest that conditions may soon
become even more extreme.
Many brick buildings only improve their appearance with
age - The Great Wall of China is still looking great after
more than 2,000 years
Durability - Fire
• Bricks are non-combustible and don't assist the spread
of fire, making them ideal for building in bushfireprone areas. Clay bricks normally do not suffer any
structural damage after a fire and can be re-used even
as load bearing walls. After all, Bricks are kiln-fired at
temperatures up to 1200 degrees Celsius (a standard
kitchen oven operates up to about 250 degrees
Celsius).
Bricks alone won't fire proof a building - timber and
plastic are flammable and glass shatters in the heat but building in brick will provide a strong foundation to
protecting your investment
Durability - Pest
• Bricks don't get attacked by pests - termites
don't eat it, rats don't gnaw at it, birds can't
stain it. Bricks are unattractive to termites
because they can't chew them - unlike timber.
Cavity brick construction offers the ultimate in
termite resistance, by eliminating timber
framing in walls.
Durability - Weather
• Most brick colours and textures hide rain streaking,
whereas plain or painted wall finishes such as render
tend to show these and if damaged, are expensive and
time-consuming to repair.
Salt-safe and exposure grade bricks
If you are building within 1km of surf coast and 100m
of non-surf coast, or on harsh soils (such as former tip
sites or converted industrial land) you should use
Exposure Grade bricks. These bricks are made to
withstand high salt conditions. In conditions like these,
Exposure Grade bricks are the most affordable building
material - designed for harsh Australian conditions
Tolerances
• Tolerances
Cleaning of Bricks
• Ideally brickwork should be cleaned as it is
laid. This is the simplest, cheapest and most
effective method. Mortar smears should be
cleaned as soon as possible using a scrubbing
brush, running water and a sponge. Acid
cleaning is only required if the mortar smears
are allowed to harden and should be viewed
as a last resort.
Degradation of Brickwork
• Fretting
• Expansion
• Poor Bonding
• Lime Pitting
Degradation - Fretting
Degradation - Fretting
• Fretting is caused by the action of salt migration in the
walling system.
• Water with salt enters the brickwork
• Water dries out & salt is left behind as salt crystals.
• Salt crystals grow in the voids within the brick. As
more salt is left behind by the evaporation of water,
the salt crystal grows larger and larger.
• The strength of the growing salt crystal can be stronger
than the elements that hold the brick together.
• If this occurs, the brick face begins to crumble and fall
away. This is also true for mortar joints.
Degradation - Fretting
• For salt attack to occur the following three
conditions are required:
– There must be salts present
– There must be water entering the wall
– The water must evaporate from the wall
• The absence of any of these conditions will
prevent salt attack.
Degradation - Fretting
• When treating fretting, "prevention is the best
cure". The source of the salt may be airborne
salt from sea spray or salts that are naturally
present in the soil, or introduced by fertilizers
and salt-water swimming pools. The use of
bore water may also provide the source of the
salt.
Degradation of Brickwork
• Fretting
• Expansion
• Poor Bonding
• Lime Pitting
Degradation - Expansion
• Bricks undergo long-term permanent
expansion over time.
• This expansion continues for the life of the
brick, but the majority of the growth occurs
early in its life.
• Most general purpose bricks have a coefficient
of expansion in the range of 0.5-1.5mm/m
(millimetres per metre) over fifteen years.
Degradation - Expansion
• The typical problems arising with expansion gaps include:
• Inadequate sealing
• Failure to ensure that the gaps are clean and that no hard
materials such as mortar droppings are left before sealing
• The use of joint fillers that are too rigid, which have
compressive strengths high enough to transfer forces
across the joint.
• However, these problems can be avoided by good
workmanship during construction. Further information on
expansion gaps is available in CBPI Manual 10; Construction
Guidelines for Clay Masonry
Degradation of Brickwork
• Fretting
• Expansion
• Poor Bonding
• Lime Pitting
Degradation – Poor Bonding
• The initial rate of absorption (IRA) is a function of the
size and extent of the porosity of the bricks. The IRA is
a measure of how quickly a brick will absorb water. The
test method for initial rate of absorption is given in
AS/NZS 4456.17.
• The ability of bricks to absorb water affects the bond
formed between brick and mortar. A tug-of-war occurs
between the bricks ability to absorb water and the
capacity of the mortar to retain water. If either the
brick or the mortar wins, a poor bond will result.
Therefore, the water retentivity of the mortar needs to
be matched to the IRA of the bricks to ensure that a
strong bond forms
Degradation of Brickwork
• Fretting
• Expansion
• Poor Bonding
• Lime Pitting
Degradation – Lime Pitting
• Lime pitting is an imperfection occurring in the surface
of a brick due to the expansion of large lime particles
just below the surface. The lime originates from the
raw materials used in the manufacture of the bricks.
• Lime pitting is observed when the lime particles are
present just below or on the surface of the brick. The
volume expansion of the lime particle, resulting from
the presence of moisture, can cause it to pop out of
the brick or break the brick surface, generating a
defect. An example of a large lime pit is shown below
Degradation – Lime Pitting
Mortar
• Mortar mixes are always specified as the proportion of
cement to lime to sand. For example, a common
mortar made from Portland cement has one part
cement, to one part lime and 6 parts of sand is
abbreviated C1:L1:S6 or 1:1:6 (the chief cementing
agent will always be expressed as one). The type of
mortar mix is classified according to the Australian
Standard AS 3700 as M1, M2, M3 or M4. The grade
chosen by the masonry designer should match the
requirements of the design. AS 3700 lists the deemedto-satisfy proportions for the various grades