BRICK
Modern brick production
Basically, the process of brickmaking has not changed since the first fired
bricks were produced some thousands of years ago. The steps used then are
used today, but with refinements. The various phases of manufacture are as
follows: securing the clay, beneficiation, mixing and forming, drying, firing,
and cooling.
1.Securing the clay
Clays used today are more varied than those used by the first brickmakers.
Digging, mining, and various methods of grinding enable the modern
manufacturer to utilize many raw materials.
Clays used in brickmaking represent a wide range of materials that include
varying percentages of silica and alumina. They may be grouped in three
classes: (1) surface clays found near or on the surface of the Earth, typically in
river bottoms; (2) shales, clays subjected to high geologic pressures and varying
in hardness from a slate to a form of partially decomposed rock; and
(3) fireclays, found deeper under the surface and requiring mining. Fireclays
have a more uniform chemical composition than surface clays or shale.
Surface clays are typically recovered by means of power shovels, bulldozers
with scraper blades, and dragline operations. Shales are recovered by blasting
and power shovels. Fireclays are mined by conventional techniques.
2.Beneficiation
Raw clays are often blended to obtain a more uniform consistency. In many
cases the material is ground to reduce large rocks or clumps of clay to usable
size and is placed in storage sheds. As additional material is stored, samples are
, blended from a cross section of the storage pile. The material is then transferred
to secondary grinders and screens (if necessary) to secure the optimum particle
size for mixing with water. In certain processes (e.g., soft-mud) the clay is
transferred directly to the mixing area, eliminating all grinding, screening, and
blending.
3.Mixing and forming
All clays must be mixed with water to form the finished product. The amount of
water added will depend on the nature of the clays and their plasticity. This
water is removed during drying and firing, which causes shrinkage of the units;
to compensate for this shrinkage the molds are made larger than the desired
finished products.
Column of clay emerging from the die of a screw extruder prior to being cut
into brick shapes.
Three basic processes are used in the forming and mixing phase. In the stiff-
mud process the clay is mixed with water to render it plastic, after which it is
forced through a die that extrudes a column of clay like the toothpaste squeezed
from a tube (see the Figure). The column gives two dimensions of the unit being
manufactured; it is cut to give the third dimension. All structural clay tile is
made by this process, as is a great percentage of brick.
Modern brick production
Basically, the process of brickmaking has not changed since the first fired
bricks were produced some thousands of years ago. The steps used then are
used today, but with refinements. The various phases of manufacture are as
follows: securing the clay, beneficiation, mixing and forming, drying, firing,
and cooling.
1.Securing the clay
Clays used today are more varied than those used by the first brickmakers.
Digging, mining, and various methods of grinding enable the modern
manufacturer to utilize many raw materials.
Clays used in brickmaking represent a wide range of materials that include
varying percentages of silica and alumina. They may be grouped in three
classes: (1) surface clays found near or on the surface of the Earth, typically in
river bottoms; (2) shales, clays subjected to high geologic pressures and varying
in hardness from a slate to a form of partially decomposed rock; and
(3) fireclays, found deeper under the surface and requiring mining. Fireclays
have a more uniform chemical composition than surface clays or shale.
Surface clays are typically recovered by means of power shovels, bulldozers
with scraper blades, and dragline operations. Shales are recovered by blasting
and power shovels. Fireclays are mined by conventional techniques.
2.Beneficiation
Raw clays are often blended to obtain a more uniform consistency. In many
cases the material is ground to reduce large rocks or clumps of clay to usable
size and is placed in storage sheds. As additional material is stored, samples are
, blended from a cross section of the storage pile. The material is then transferred
to secondary grinders and screens (if necessary) to secure the optimum particle
size for mixing with water. In certain processes (e.g., soft-mud) the clay is
transferred directly to the mixing area, eliminating all grinding, screening, and
blending.
3.Mixing and forming
All clays must be mixed with water to form the finished product. The amount of
water added will depend on the nature of the clays and their plasticity. This
water is removed during drying and firing, which causes shrinkage of the units;
to compensate for this shrinkage the molds are made larger than the desired
finished products.
Column of clay emerging from the die of a screw extruder prior to being cut
into brick shapes.
Three basic processes are used in the forming and mixing phase. In the stiff-
mud process the clay is mixed with water to render it plastic, after which it is
forced through a die that extrudes a column of clay like the toothpaste squeezed
from a tube (see the Figure). The column gives two dimensions of the unit being
manufactured; it is cut to give the third dimension. All structural clay tile is
made by this process, as is a great percentage of brick.
