Post on 14-Jul-2015
PROTECTIVE & DECORATIVE COATINGS:-
Special materials are used in the finishing coats of plastering or over the plastered surfaces to meet one or more of specific requirement such as decorative appearance, high durability,fire – proofing,heatinsulation,sound insulation,earlycompletion,high strength,etc..
Some of these special materials are given below:- Plaster of paris.
acoustic plasters.
granite silicon plaster.
Asbestos marble plaster.
keene’s cement.
Parian cement.
Snow- crete and colour crete cement.
barium plaster.
plaster’s putty.
PLASTER OF PARIS:- Quick-setting gypsum plaster consisting of a fine,
white powder, calcium sulfate hemihydrate.
Used since ancient times, plaster of paris is so called because gypsum was early used near Paris to make plaster and cement.
Plaster of paris is also used to hold parts of ornamental plasterwork placed on ceilings and cornices.
Used in medicine to make plaster casts to immobilize broken bones while they heal.
Some modern sculptors work directly in plaster of paris.
The speed at which the plaster sets gives the work a sense of immediacy and enables the sculptor to achieve the original idea quickly.
ACOUSTIC PLASTERING:-Acoustic plaster is plaster which contains fibres or
aggregate so that it absorbs sound.
Such plaster is applied in thicknesses of up to 1.5 inches. As compared with other sound insulation, it is easy to apply and is fireproof but it can be more fragile, being affected by physical stress and humidity.
Acoustic plaster is used in construction of rooms which require good acoustic qualities such as auditoria and libraries.
BARIUM PLASTER:- This is made from barium sulphate and is employed
as a final coat to the walls of X-ray rooms.
This finish acts as protection for the persons working in X- rays rooms as this surface absorbs the X-rays.
Walls can be covered with lead to give any desired protection and there is no better protection than this method can afford ,provided the lead has a sufficient thickness and is properly laid.
Barium plaster has been advocated as an X-ray protective wall material.
GRANITE SILICON PLASTER:- Granite is a ready-to-use render made
from a silicone resin mixed with
coloured quartz or marble aggregate.
The product is weather resistant, impact
resistant and washable.
This type of plaster possess the quick –
setting and highly elastic properties
This material therefore, when used in
plastering is not liable to crack.
It provides a hydrophobic layer that is
permeable to water vapour.
The product is available in three finishes:
Marble, Quartz and Natural.
ASBESTOS MARBLE PLASTER:- This is a mixture of finely crushed
marble,asbestos and cement.
It is used only for finishing coat,this
material presents a beautiful, marble
like finish.
A new plaster surface will give you 5 to
8 years of good service, depending on
chemical maintenance and is usually
the least expensive resurfacing option.
KEENE’S CEMENT:- A hard-finish gypsum plaster to which alum
has been added and which is used chiefly as
a gauging plaster in lime mortar for walls (as
of hospitals, stores, railroad stations)
It is plaster of paris which is calcined with
alum.
This material is the hardest form of gypsum
plaster and sets within few days.
It is white in colour and takes up a high glass
–like polish.
It is used for highly decorative plastering
work and ornamental work,due to its
polishing characteristics.
PARIAN CEMENT:- A hard finish plaster, similar to
Keene's cement plaster,
except borax is used as an
additive in place of alum.
It is also plaster of paris which
is calcined with borax.
It is also used for interior work.
This type of cement is
preferred for surfaces with
large areas.
SNOW- CRETE AND COLOUR CRETE
CEMENTS:-
These are the trade names given to
the white and coloured cements
respectively
White cement is used for both
external and internal works
Coloured cements are used for
finishing coat of external works
These coloured cements present a
decorative appearance to the
surface being plastered.
PLASTER’S PUTTY:-
This is prepared by slaking of pure lime with water,bringing it to creamy consistency,then straining it through a fine sieve and finally allowing it to evaporate until sufficiently stiff to use
It is normally used as a last coat to internal walls which are intended to be colouredlater.
their self-healing nature reduces cracking problems.
they can reduce condensation problems.
SIRA BITE:-
This material is obtained by slacking plaster of paris with petroleum
It is quick setting and gives a white hard surface on drying
It posses good workability and high fire resisting properties
It is used for plastering of internal work for fire resistant construction
SCAGLIOLA:-
This material is an imitation marble which is obtained by dissolving keene’s cement and colouring pigments in glue
This material is used for pilasters , panels , columns, etc.
Scagliola is a form of plaster, traditionally gypsum, which imitates decorative stone and has been widely used for the decoration of walls, columns, floors, fireplaces and table tops.
the use of scagliola is more commonly associated with the imitation of the finest marbles on a much larger scale, without any joints or defects, and for columns and pilasters in particular
THISTLE HARD WALL:-
This material is a product of high grade gypsum which has got the capacity of carrying sand
It sets rapidly and produces an excellent finish
It is normally used for internal work
High impact resistance and quicker drying surface. Suitable for application by hand, or mechanical plastering machine, to most masonry backgrounds.