Which of the following is not a plaster type based on material?
🔬 Understanding Plaster Classification
Plaster is a building material used for coating, protecting, and decorating internal walls and ceilings. Plasters are typically classified based on their primary binding material, which is the component that hardens and holds the mixture together.
⚖️ Detailed Analysis of the Options
Let's evaluate each option to determine if it serves as a primary binder for a type of plaster.
(a) Cement Plaster
Is it a plaster type? YES. This is one of the most common types of plaster. It uses Portland cement as the binder, mixed with sand and water. It creates a strong, hard, and durable surface suitable for both internal and external walls.
(b) Gypsum Plaster
Is it a plaster type? YES. This type of plaster uses gypsum (calcium sulfate) as the primary binder. It is known for providing a very smooth, crack-free finish and is used exclusively for interior surfaces. It sets quickly and does not require water curing.
(d) Lime Plaster
Is it a plaster type? YES. This is a traditional type of plaster that uses lime (calcium hydroxide) as the binder. It is known for its high workability, breathability, and flexibility. It is often used in the restoration of historic buildings.
(c) Pozzolana
Is it a plaster type? NO. Pozzolana is not a primary binding material used to make plaster on its own.
What it is: Pozzolanas (like fly ash, silica fume, or volcanic ash) are supplementary cementitious materials (SCMs). They are siliceous or aluminous materials that do not have cementing properties on their own but will, in the presence of moisture, react chemically with calcium hydroxide (lime) to form compounds with cementitious properties.
How it's used: It is used as an admixture in concrete and mortars or as a component in the manufacture of blended cements (like Portland Pozzolana Cement). It enhances properties like long-term strength and durability, but it is not a standalone plaster type.
📋 Additional Information: Plaster Thickness and Ratios
The application of plaster has standard guidelines for thickness and mix ratios to ensure proper performance.
- General Wall Plaster: The typical thickness is 12 mm to 15 mm. A common cement-sand mix ratio for this is 1:6 for internal walls.
- Ceiling Plaster: The thickness is generally kept lower, around 6 mm, to reduce the weight on the ceiling. A richer mix of 1:3 is often used to ensure strong adhesion.