Gypsum is a soft sulfate mineral composed of calcium
sulfate dihydrat, with the chemical formula CaSO4·2H2O
COLOR- Colorless to white; may be yellow, tan, blue, pink,
brown, reddish brown or gray due to impurities.
MANUFACTURING PROCESS OFCALCINED GYPSUM
The raw material gypsum is sorted and washed with water
for removal of sand and other impurities.
The lumps thus obtained are then dried and powdered in
The dried gypsum powder is calcined in a rotary drum calciner
at a temperature of 160ºC to 180ºC.
The process of calcination is done over a period of about
2 hours. the temperature so that one and half molecules of
water is removed to convert the gypsum (CaSo4 2 H2O) into
plaster of Paris (CaSo4 ½ H2O).
After cooling the product (plaster of Paris) is further
pulverized to a fineness of 150 mesh and packed in air tight
polythene lined gunny bags to avoid the plaster of Paris from
absorption of moisture.
160ºC to 180ºC
about 2 hrs.
Advantage of p o p
It expands very slightly on setting.
It is easy to spread and level.It mixes up easily with water.
It has no appreciable chemical action on paint and does
not cause alkali attack.
Tiles and blocks of plaster of Paris have the specific
advantage of lightness and high fire resistance.
Plaster of Paris gives a decorative interior finish.
Disadvantage of p o p
Gypsum plaster is not suitable for exterior finish as it can
not be used in damp finish.
Cement can not be mixed with plaster of Paris.
It is more expensive than cement or cement lime plaster.
The labor cost for applying plaster of Paris is high.
Gypsum is a rock like mineral commonly found in the
earth’s crust, extracted, processed and used by Man in
construction or decoration in the form of plaster and
alabaster since 9000 B.C.. Plaster was discovered in
Catal-Huyuk in Asia in an underground fresco, and in
Israel Gypsum floor screeds were found from 7000 B.C.
During the time of the Pharaohs, Gypsum was used as
mortar in the construction of the Cheops Pyramid (3000
B.C.). In the Middle Ages and the Renaissance, decorations
and artistic creations were made of plaster. Since then,
the range of construction-related uses have continued to
HISTORY OF GYPSUM
gypsum rock is
quarries or mine
2.Large rocks are
crushed into small
3.The mill reduces small
rocks to a very fine,
chalk-like powder called
4.The land plaster is
heated in large kettles to
remove most of the water
from the plaster.
Stucco holding tank
5.Calcined land plaster,
called stucco, is fed
from a holding bin to the
mixer by a screw
6.In the mixer, water is added
back to the stucco
to form a slurry, and foam is
added to the slurry to make
the wallboard more
7.T he board forming line starts with two large rolls
of recycled paper or fiberglass mats. The slurry is
poured onto the bottom sheet and is immediately
covered by the facing sheet from the other roll.
8. the board travels down a
long conveyor line in a single continuous
piece. During this trip, water rehydrates
the stucco, causing it to harden.
Cut –off knife
9. the end of the line, a blade cuts the
hardened board into various lengths.
10.Here the cut lengths are turned
face-side up to protect the face paper
or mat, then fed into the kiln.
The board kiln completes the
drying process, leaving the gypsum
board virtually moisture-free.
MANUFACTURE OF GYPSUM board
Major varieties of gypsum
Satin spar Pearly, fibrous masses
Transparent and bladed
Alabaster Fine-grained, slightly colored
SATIN SPAR ALABASTER ALABASTERSelenite
Type of gypsum:-
Natural gypsum or,
Synthetic gypsum is k/n as fgd.
Uses of gypsum
Gypsum can be used :-
juice extraction of some fruits and vegetables.
Use of gypsum in building
Gypsum building materials are used in all construction
types (residential, non-residential, new or refurbished)
Plasterboard is used for partitions and the lining of
walls, ceilings, roofs. The properties of
plasterboard can be modified to meet specific requirements
, such as fire resistance, humidity resistance, shock
Plaster powder, mixed with water, manually or through the
use of silo-supplied spray systems, are used to create
an effective and aesthetically-pleasing lining for brick and
block walls, and for ceilings.
Gypsum fibreboard is used for partitions and the lining of
walls, ceilings, roofs and floors. Standard Gypsum
fibreboard offers good performance when it comes to
shock resistance, sound insulation and humidity resistance.
Use of gypsum in medical
Gypsum is also used in the medical industry.
Gypsum is also used to clean teeth and is present
in many forms of toothpaste.
It is used to set the broken bones & sprain.
It is used in filling of teeth cavities.
Use of gypsum in agriculture
Be a source of Calcium and Sulphate Sulphur
for plant growth.
Gypsum is added to soil to make the soil better able
to absorb moisture.
Gypsum is used in water to settle dirt.
Gypsum board is the generic name for a family of panel
products that consist of a non-combustible core.
All gypsum panel products contain gypsum cores; however
, they can be faced with a variety of different materials,
including paper and fiberglass mats.
Gypsum board is often called drywall, wallboard, or
Standard size of gypsum board
Standard size gypsum boards are 48 inches wide and 8,
10, 12 or 14 feet long.
The 48 inch width is compatible with standard framing methods in
which studs or joists are spaced 16 inches and 24 inches.
other lengths and widths of gypsum board are available from
the manufacturer on special order.
Gypsum is also an indefinitely recyclable raw material
You can always reuse Gypsum because the chemical composition
of the raw material in the products remains unchanged
the waste of is used to make the same product again.
Properties of gypsum
Gypsum is fire protective
Gypsum is non-combustible and able to delay a fire’s
spread up to 4 hours.
Gypsum regulates sound.
Gypsum walls, ceilings and floors together with
insulation materials create quiet zones in the house
or business environment.
Gypsum is impact resistant.
The Gypsum Industry provides plasterboards, gypsum
fibreboards and plaster blocks with a degree of hardness
equivalent to a thick wall heavy masonry construction.
Gypsum is easy to install and to dismantle
Gypsum is multifaceted, multipurpose, supple and aesthetic
Advantage of gypsum board
Gypsum board walls and ceilings have a number of
Ease of installation