Plaster is a protective or decorative coat that is applied on walls, ceilings, floors, etc to protect them against weathering actions, chemicals, fungus, etc, and also to achieve a smooth surface.
Commonly; lime plaster and cement plaster are used in plastering work. In this article, we will discuss cement plaster.
The blended form of cement, sand, and water in definite proportion is cement plaster.
It is also known as cement sand plaster.
PPC cement is commonly used for cement plaster rather than OPC cement.
The generally used mixed proportion of cement and sand for cement plaster are 1: 4, 1:5, and 1:6.
For Internal plaster – 1:6 or 1:5
For External plaster – 1:4
For Ceiling plaster – 1:3
Cement plaster is quite similar to cement mortar. The main difference is that fine-grained sand is used in cement plaster whereas coarse-grained sand is in cement mortar.
|Read Also: Plastering|
2. Grade of Cement Plaster
|Grade Name||Mortar Mix (by Loose Volume)||Compressive Strength at 28 days (in N/mm2)|
|MM 0.7||1||8||0.7 to 1.5|
|MM 1.5||1||7||1.5 to 2.0|
|MM 3||1||6||3.0 to 5.0|
|MM 5||1||5||5.0 to 7.5|
|MM 7.5||1||4||7.5 to above|
3. Preparation of Cement Plaster
It can be prepared in the following steps:
a. Selection and Preparation of Ingredients
~ Grade of cement should be chosen based on the requirement. Commonly; PPC cement is used for preparing plaster.
~ Sand having fine grains should be chosen. The grading limit of sand for cement plaster is given below.
|IS Sieve Size||Percentage Passing|
|4.75 mm||95 – 100|
|2.36 mm||95 – 100|
|1.18 mm||90 – 100|
|600 micron||80 – 100|
|300 micron||20 – 65|
|100 micron||0 – 15|
~ Water having a PH value between 6 and 8 should be used.
b. Mixing of Ingredients
Mixing of cement, sand, and water can be done manually or by machine mixing. The ratio of cement and sand is determined by the required grade of plaster as stated above.
c. Transportation and Application of Plaster to the Surfaces
Thus prepared plaster is transported to the desired place and is applied to the surface manually or by using plastering pumps.
a. This plaster is quite durable and has a closed pore structure that inhibits the circulation of moisture through it.
b. It gains maximum efficiency in a short time as compared to lime plaster.
c. It can be used for plastering internal as well as external surfaces.
d. It is resistive towards vegetation growth and chemical actions to a certain degree.
e. It is fire resistive to a certain degree. ( Excessive firing may result in spalling of plaster. )
a. Requirement of pre-curing and post-curing for supporting hydration reaction.
b. It has low tension and flexural strength; so cracks are formed quickly.
c. It can’t be applied on smooth surfaces.
d. It is not a rust inhibitor.
|Read Also: Curing of Concrete|
|Read Also: 26 Types of Concrete|