Categories: Civil Engineering

Plaster

Plaster can be described as Lean Mortar primarily used to cover the surface of masonry. They are lean combinations of fillers such as sand or crushed stones (lime, cement). And the method of covering surfaces is called Plastering.

In particular, plaster is used for two special purposes.

  • For protection
  • For decoration

In protective coating, plaster protects bricks or stones against direct disruptive attacks, such as wind, rain, and toxic industrial gases. Meanwhile, plasters help provide many attractive building shades and decorative finishes.

Cement Plasters

These are the homogeneous lean mixture of Portland cement, water and sand. It was found to be ideal for all types of plastering work, including security and decorative finishes.

Cement plasters have the most common ratio (1: 3).

  • Exterior surfaces (1: 3)
  • Interior surfaces (1: 4)

However, due to the design of building, the sand ratio can be increased to as much as 8 (1:8). Cement plasters are normally only applied in one coat. It is appropriate that at least 3 days after its application, the plaster surface should be kept wet.

Gypsum Plaster

These are plasters that use gypsum instead of cement or limestone as a bonding material. Plaster is also used for wall and ceiling construction for fancy and architectural decorations. Its key features are:

  • They have a lot of fire resistance
  • Its thermal and acoustic insulation is comparatively higher
  • They are fast setting and hardening
  • They spread and contract very little

How Gypsum Plasters are prepared?

It consists of natural gypsum rock, a hydrated calcium sulphate. This rock is burnt at a proper (110 centigrade) temperature. Most crystallization water is extracted at this temperature.

The product is an anhydrite, also known as Parisian plaster. Gypsum plasters are carefully calcined to avoid insufficient or excessive burning. Powdered is the calcined gypsum. When mixed with water , it forms a paste that starts settling and hardening easily.

Types of Gypsum Plaster

It is normal to use the following types.

Ready Mix: This is a Paris and Sand plaster in a predetermined shape in a dry mix form. Its insulation properties are three times higher than those of standard cement or lime render.

Gypsum Neat Plaster: is the result of the desired amount of dry sand mixing commercial grade plaster of Paris. The dry mix can then be reduced to a normal paste with water and mixed with trowels at the same time.

Keen’s Cement Plasters: It is a gypsum plaster with a high density that can be finely polished on its finished surface. Plasters are produced by combining sufficient Gypsum Plaster proportions with lime pulverized lime (hydrated lime). They are particularly suitable for a short time to provide a hard surface on the foundation.

Stucco Plasters: It is typically used in decorative applications. It is applied to the exterior surface of the building and gives the structure a marble like finish. Cement or liming is typically used in this type as a binding material.

All of these types are usually applied in three coats (base, middle and final course). In order to achieve a shine the finishing coat is finished with a soft fabric. The resulting surface is therefore solid, secure and attractive.

Adam

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