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Questions and Answers
Excess of silica makes the brick ______ and weak on burning.
Excess of silica makes the brick ______ and weak on burning.
brittle
If alumina is present in excess of the specified quantity, it produces ______ in brick on drying.
If alumina is present in excess of the specified quantity, it produces ______ in brick on drying.
cracks
Lime normally constitutes less than 10 per cent of ______.
Lime normally constitutes less than 10 per cent of ______.
clay
Lime in brick clay has the effect of reducing the ______ on drying.
Lime in brick clay has the effect of reducing the ______ on drying.
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Excess of lime causes the brick to ______ and the brick loses its shape.
Excess of lime causes the brick to ______ and the brick loses its shape.
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Magnesia rarely exceeding 1 percent affects the ______ and makes the brick yellow.
Magnesia rarely exceeding 1 percent affects the ______ and makes the brick yellow.
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Iron oxide constituting less than 7 percent of clay, imparts ______ colour on burning when excess of oxygen is available.
Iron oxide constituting less than 7 percent of clay, imparts ______ colour on burning when excess of oxygen is available.
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Improved kiln designs and more advanced ______ have all contributed to advancing the brick industry.
Improved kiln designs and more advanced ______ have all contributed to advancing the brick industry.
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Clay is one of the most abundant natural ______ materials on earth.
Clay is one of the most abundant natural ______ materials on earth.
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After pugging, the tempered clay goes through a de airing chamber that maintains a vacuum of 15 to 29 in.(375 to 725 mm) of ______.
After pugging, the tempered clay goes through a de airing chamber that maintains a vacuum of 15 to 29 in.(375 to 725 mm) of ______.
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The soft-mud or molded process is particularly suitable for clays containing too much ______ to be extruded by the stiff-mud process.
The soft-mud or molded process is particularly suitable for clays containing too much ______ to be extruded by the stiff-mud process.
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Clays are mixed to contain 20 to 30 percent ______ and then formed into brick in molds.
Clays are mixed to contain 20 to 30 percent ______ and then formed into brick in molds.
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To prevent clay from sticking, the molds are lubricated with either ______ or water to produce “sand-struck” or “water-struck” brick.
To prevent clay from sticking, the molds are lubricated with either ______ or water to produce “sand-struck” or “water-struck” brick.
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This process is particularly suited to clays of very low ______.
This process is particularly suited to clays of very low ______.
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Clay is mixed with a minimal amount of ______ (up to 10 percent), then pressed into steel molds under pressures.
Clay is mixed with a minimal amount of ______ (up to 10 percent), then pressed into steel molds under pressures.
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Wet brick from molding or cutting machines contain 7 to 30 percent ______, depending upon the forming method.
Wet brick from molding or cutting machines contain 7 to 30 percent ______, depending upon the forming method.
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The brick are typically placed by ______ or mechanical means.
The brick are typically placed by ______ or mechanical means.
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Fuel may be ______ gas, coal, sawdust, methane gas from landfills or a combination of these fuels.
Fuel may be ______ gas, coal, sawdust, methane gas from landfills or a combination of these fuels.
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The manufacturing process has six general phases, including _______________ of raw materials.
The manufacturing process has six general phases, including _______________ of raw materials.
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Surface clays, shales and some fire clays are mined in open pits with _______________ equipment.
Surface clays, shales and some fire clays are mined in open pits with _______________ equipment.
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To break up large clay lumps and stones, the material is processed through _______________ machines.
To break up large clay lumps and stones, the material is processed through _______________ machines.
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The material is processed through _______________ vibrating screens to control particle size.
The material is processed through _______________ vibrating screens to control particle size.
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Tempering produces a _______________, plastic clay mass.
Tempering produces a _______________, plastic clay mass.
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Water is added to the clay in a _______________ to achieve tempering.
Water is added to the clay in a _______________ to achieve tempering.
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There are three principal processes for forming brick: _______________-mud, soft-mud and dry-press.
There are three principal processes for forming brick: _______________-mud, soft-mud and dry-press.
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In the stiff-mud or extrusion process, water in the range of 10 to 15 percent is mixed into the clay to produce _______________.
In the stiff-mud or extrusion process, water in the range of 10 to 15 percent is mixed into the clay to produce _______________.
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The final phase of the manufacturing process is _______________ and storing finished products.
The final phase of the manufacturing process is _______________ and storing finished products.
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In a tunnel kiln, bricks are loaded onto ______ cars, which pass through various temperature zones as they travel through the tunnel.
In a tunnel kiln, bricks are loaded onto ______ cars, which pass through various temperature zones as they travel through the tunnel.
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Firing may be divided into five general stages: 1) final drying (evaporating free water); 2) dehydration; 3) oxidation; 4) ______; and 5) flashing or reduction firing.
Firing may be divided into five general stages: 1) final drying (evaporating free water); 2) dehydration; 3) oxidation; 4) ______; and 5) flashing or reduction firing.
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Although the actual temperatures will differ with ______ or shale, final drying takes place at temperatures up to about 204 ºC.
Although the actual temperatures will differ with ______ or shale, final drying takes place at temperatures up to about 204 ºC.
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De-hacking is the process of unloading a ______ or kiln car after the brick have cooled, a job often performed by robots or machines.
De-hacking is the process of unloading a ______ or kiln car after the brick have cooled, a job often performed by robots or machines.
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When a desirable amount of lime is present in the ______, it results in good bricks, but if in excess, it changes the colour of the brick from red to yellow.
When a desirable amount of lime is present in the ______, it results in good bricks, but if in excess, it changes the colour of the brick from red to yellow.
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Pebbles, Gravels, Grits : do not allow the ______ to be mixed thoroughly and spoil the appearance of the brick.
Pebbles, Gravels, Grits : do not allow the ______ to be mixed thoroughly and spoil the appearance of the brick.
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On burning green bricks, the organic matter gets charred and leave pores making the bricks ______; the water absorption is increased and the strength is reduced.
On burning green bricks, the organic matter gets charred and leave pores making the bricks ______; the water absorption is increased and the strength is reduced.
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Alkalis (Alkaline Salts) : forming less than 10 per cent of the raw ______, are of great value as fluxes, especially when combined with silicates of alumina.
Alkalis (Alkaline Salts) : forming less than 10 per cent of the raw ______, are of great value as fluxes, especially when combined with silicates of alumina.
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Cooling is an important stage in brick manufacturing because the rate of cooling has a direct effect on ______.
Cooling is an important stage in brick manufacturing because the rate of cooling has a direct effect on ______.
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When bricks come in contact with ______, water is absorbed and the alkalis crystallise.
When bricks come in contact with ______, water is absorbed and the alkalis crystallise.
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On drying, the ______ evaporates, leaving behind grey or white powder deposits on the brick.
On drying, the ______ evaporates, leaving behind grey or white powder deposits on the brick.
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Efflorescence should always be ______ brushed away before rendering or plastering a wall.
Efflorescence should always be ______ brushed away before rendering or plastering a wall.
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Sulphur is usually found in clay as the sulphate of ______, magnesium, sodium, potassium or iron.
Sulphur is usually found in clay as the sulphate of ______, magnesium, sodium, potassium or iron.
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If there is ______ in the clay and insufficient time is given during burning for proper oxidation of carbon and sulphur, the latter will cause the formation of a spongy, swollen structure in the brick.
If there is ______ in the clay and insufficient time is given during burning for proper oxidation of carbon and sulphur, the latter will cause the formation of a spongy, swollen structure in the brick.
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A large proportion of ______ water generally causes clay to shrink considerably during drying.
A large proportion of ______ water generally causes clay to shrink considerably during drying.
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The use of water containing small quantities of magnesium or calcium carbonates, together with a ______ fuel often causes similar effects as those by sulphur.
The use of water containing small quantities of magnesium or calcium carbonates, together with a ______ fuel often causes similar effects as those by sulphur.
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The brick will be decoloured by white ______ if there is carbon in the clay and insufficient time is given during burning for proper oxidation of carbon and sulphur.
The brick will be decoloured by white ______ if there is carbon in the clay and insufficient time is given during burning for proper oxidation of carbon and sulphur.
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Efflorescence is a phenomenon that spoils the ______ of the brick.
Efflorescence is a phenomenon that spoils the ______ of the brick.
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Study Notes
Chemical Composition of Clay
- Excess silica in clay makes bricks brittle and weak on burning
- Alumina (Al2O3) absorbs water and makes clay plastic, but excess alumina causes cracks in brick on drying
- Lime (CaO) in clay:
- Reduces shrinkage on drying
- Helps silica melt and bind on burning
- Lowers fusion point in carbonated form
- Excess lime causes bricks to melt and lose shape
- Increases lime content to produce buff-burning bricks
- Magnesia (MgO) in clay:
- Affects color, making bricks yellow on burning
- Causes clay to soften at a slower rate
- Reduces warping
- Iron (Fe) in clay:
- Imparts red color on burning with excess oxygen
- Improves impermeability and durability
- Lowers fusion point, especially as ferrous oxide
- Gives strength and hardness
Manufacturing of Bricks
- Raw materials: clay, one of the most abundant natural mineral materials on earth
- Phases of manufacturing:
- Mining and storage of raw materials
- Preparing raw materials
- Forming the brick
- Drying
- Firing and cooling
- De-hacking and storing finished products
Manufacturing Process
- Mining and storage:
- Surface clays, shales, and fire clays are mined in open pits
- Raw materials are transported to plant storage areas
- Storing sufficient quantities ensures continuous brick production
- Preparation:
- Breaking up large clay lumps and stones through size reduction machines
- Processing through inclined vibrating screens to control particle size
- Forming:
- Three principal processes: stiff-mud, soft-mud, and dry-press
- Stiff-mud process:
- Mixing water with clay to produce plasticity
- De-airing removes air holes and bubbles, giving clay increased workability and plasticity
- Soft-mud process:
- Mixing clay with 20-30% water
- Forming into brick in molds
- Dry-press process:
- Mixing clay with minimal water (up to 10%)
- Pressing into steel molds under pressure
Drying and Firing
- Drying:
- Wet brick contains 7-30% moisture, depending on forming method
- Evaporating water in dryer chambers at temperatures ranging from 100°F to 400°F
- Drying time varies with different clays, usually between 24 to 48 hours
- Firing (burning):
- Firing brick between 10 and 40 hours, depending on kiln type and variables
- Types of kilns: tunnel kiln, periodic kiln
- Fuel: natural gas, coal, sawdust, methane gas, or combination
- Firing stages: final drying, dehydration, oxidation, vitrification, and flashing or reduction firing
Harmful Substances in Bricks
- Lime:
- Excess lime causes disintegration of bricks
- Lime in lumps absorbs moisture, swells, and causes disintegration
- Pebbles, gravels, and grits:
- Do not allow clay to mix thoroughly
- Spoil appearance of brick
- Bricks with pebbles and gravels may crack
- Organic matter:
- On burning, organic matter gets charred, leaving pores
- Increases water absorption, reduces strength
- Alkalis (alkaline salts):
- Excess alkalis make clay unsuitable for bricks
- Melt clay on burning, making bricks unsymmetrical
- Cause efflorescence (grey or white powder deposits) on bricks
- Sulphur:
- Found in clay as sulphate or iron sulphide
- Causes formation of spongy, swollen structure in brick
- Decolours brick with white blotches
- Water:
- Free water causes clay to shrink on drying
- Combined water causes shrinkage on burning
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Description
This quiz covers the impact of silica, alumina, and lime on brick clay, including their effects on brick strength, plasticity, and burning. Learn how excess or deficiency of these components can affect brick quality.