GYPSUM PLASTER | PROPERTIES OF GYPSUM PLASTER | USES OF GYPSUM PLASTER

GYPSUM PLASTER

Gypsum is hydrated sulphate of calcium (CaSO4 ⋅ 2H2O). It is not available in nature in pure form but contains impurities such as alumina, calcium carbonate, magnesium carbonate and silica. It is a white crystalline substance less soluble in water but soluble in hydrochloric acid. As a binding material, it sets and hardens quickly.

Gypsum heated between 120 to 180°C loses about 14.7% of the water of crystallisation in the form of steam and forms calcium sulphate hemihydrate, known as plaster of Paris. Further heating leads to the removal of all water and forms calcium sulphate anhydrate. This plaster is mixed with a small accelerator (i.e., alum potassium sulphate, raw gypsum) to make anhydrous or Keene’s gypsum plaster.

 

PROPERTIES OF GYPSUM PLASTER

Following are the properties of gypsum plaster:

(i) It is light in weight and unaffected by bacteria.

(ii) It shows food adhesion to fibrous materials but is only slightly soluble in water.

(iii) It sets with less change in volume and shows negligible shrinkage on drying.

(iv) Because of its quick-drying property, finishing coats can be applied immediately.

(v) A porous gypsum is an important sound-absorbing material.

TECHNICAL SPECIFICATIONS OF GYPSUM PLASTER

USES OF GYPSUM PLASTER

(i) It is used for ornamental plasterwork.

(ii) It is used as a heat-insulating material.

(iii) Gypsum plasterboards are light in weight, fire-proof and easy to work which are used for a ceiling for internal lining of walls and for partition walls.

(iv) Gypsum blocks are very useful in the construction of non-load bearing partition walls.

(v) Scatted gypsum piles (acoustic tiles) are used for large offices and auditorium to reduce echo.

(vi) Plaster of Paris is used in dentistry, artwork, pottery, etc. 

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