Masonry. History Oldest Brickwork 7500BC Romans first to Kiln Fire Become a Staple of the Building...

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Masonry

History

• Oldest Brickwork 7500BC

• Romans first to Kiln Fire

• Become a Staple of the Building Industry after Great London Fire

• 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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Note – Clay is not Compressed

Shrinkage due tono compaction

Distortion due tono compaction

Voids due toLack of Compaction

Edges not properlyformed

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 likeAppearance

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

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”)

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• 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 bushfire-prone 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 bricksIf 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

• 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.

• 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.

• 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.

• 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

• 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

• 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 deemed-to-satisfy proportions for the various grades

Masonry. History Oldest Brickwork 7500BC Romans first to Kiln Fire Become a Staple of the Building...

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