OKAN INSAAT
What Is Plaster ?
The term plaster can refer to plaster of Paris, lime plaster, or cement plaster. This article deals mainly with plaster of Paris.
Plaster of Paris is a type of building material based on calcium sulphate hemihydrate, nominally CaSO4·H2O. It is created by heating gypsum to about 150 °C.
A large gypsum deposit at Montmartre in Paris is the source of the name.[1][2] When the dry plaster powder is mixed with water, it re-forms into gypsum. Plaster is used as a building material similar to mortar or cement. Like those materials plaster starts as a dry powder that is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after drying, and can be easily manipulated with metal tools or even sandpaper. These characteristics make plaster suitable for a finishing, rather than a load-bearing material.
Properties Of Plaster
- Unburnable
- Temperature Saver
- Soundproff
- Lightness
- Processing and Fixing Easiness
- Easily Shaping
- Anti-Bacterial
- Balancing Moisture
- Breathing Surfaces
- Anti-Firing
- Suitable For Every Surfaces
Uses Of Plaster
Cement plaster is a mixture of suitable plaster, sand, portland cement and water which is normally applied to masonry interiors and exteriors to achieve a smooth surface. Interior surfaces sometimes receive a final layer of gypsum plaster. Walls constructed with stock bricks are normally plastered while face brick walls are not plastered. Various cement-based plasters are also used as proprietary spray fireproofing products. These usually use vermiculite as lightweight aggregate. Heavy versions of such plasters are also in use for exterior fireproofing, to protect LPG vessels, pipe bridges and vessel skirts.
Plaster is widely used as a support for broken bones; a bandage impregnated with plaster is moistened and then wrapped around the damaged limb, setting into a close-fitting yet easily removed tube, known as an orthopedic cast; however, this is slowly being replaced by a fibreglass variety.
Plaster is also used within radiotherapy when making immobilization casts for patients. Plaster bandages are used when constructing an impression of the patients head and neck, and liquid plaster is used to fill the impression and produce a plaster bust. Perspex is then vacuum formed over this bust creating an immobilization shell.
Plasters have been in use in passive fire protection, as fireproofing products, for many decades.
The finished plaster releases water vapor when exposed to flame, acting to slow the spread of the fire, for as much as an hour or two depending on thickness. It also provides some insulation to retard heat flow into structural steel elements, that would otherwise lose their strength and collapse in a fire. Early versions of these plasters have used asbestos fibres, which have by now been outlawed in industrialized nations and have caused significant removal and re-coating work. More modern plasters fall into the following categories:
- Fibrous (including mineral wool and glass fiber)
- Cement mixtures either with mineral wool or with vermiculite
- Gypsum plasters, leavened with polystyrene beads, as well as chemical expansion agents to decrease the density of the finished product
Plaster
