What is Gypsum and Why is It Used in Cement Plastering? Full Explanation

Gypsum is a naturally occurring mineral that has been used in construction for centuries. It is a soft, white powder that is easily mixed with water to form a paste. When gypsum paste dries, it hardens into a strong and durable material.

Gypsum is often used in cement plastering because it has a number of advantages over traditional cement plaster. Gypsum plaster is lighter, easier to apply, and dries faster than cement plaster. It is also more fire-resistant and has better soundproofing properties.

What is Gypsum?

First things first, let’s demystify gypsum. Gypsum is a naturally occurring mineral composed of calcium sulfate dihydrate. In its raw form, it’s a soft, white, or gray mineral found in sedimentary rock deposits. But what makes gypsum so special is its unique property of being able to transform into a hard, durable material when mixed with water. This magical transformation is what makes gypsum the star of the show in the construction industry.

IS Gypsum Used with Cement for Plastering?

First of all, gypsum is used in cement during the production time. Simply put, when cement is manufactured, 5% of gypsum is used there. It helps to control one of the major components of cement, C₃A or Tricalcium Aluminate. This component of cement reduces the setting time and hardens the cement faster. For this reason, gypsum is used to control it and increase the setting time.

Now, if you are willing to use Gypsum for plastering then you will need to use Gypsum plastering instead of cement plastering. Gypsum plaster is created by heating gypsum to remove the water content, leaving behind a fine powder. For such a kind of plaster, you won’t need to use cement and sand, just you will need to use the pre-mix gypsum powder with water.

This powder, when mixed with water, forms a paste that can be applied to walls and ceilings, resulting in a smooth, even surface. Gypsum plaster is renowned for its versatility and is used extensively in both residential and commercial construction.

Types of Gypsum Plaster

Basically, there are three types of Gypsum plaster available. Here are they –

1. Standard Gypsum Plaster

Standard gypsum plaster, also known as beta hemihydrate gypsum plaster, is the most common type of gypsum plaster. It is made by heating gypsum rock to a temperature of around 120-180°C. This process drives off some of the water molecules in the gypsum, leaving behind a powder that is mixed with water to form plaster. 

2. Anhydrite Gypsum Plaster

Anhydrite gypsum plaster is made by heating gypsum rock to a temperature of around 1700°C. This process drives off all of the water molecules in the gypsum, leaving behind a powder that is mixed with water and a retarder to form plaster. 

3. Hemihydrate Gypsum Plaster

Hemihydrate gypsum plaster, also known as plaster of Paris, is made by heating gypsum rock to a temperature of around 120-180°C. This process drives off some of the water molecules in the gypsum, leaving behind a powder that is mixed with water to form plaster. 

Why Gypsum Cement is used in Plastering instead of Traditional Standard Cement?

Now, let’s address the elephant in the room – why choose gypsum cement plastering over traditional cement plaster Here are the key factors that make gypsum plaster a preferred choice

Benefits Gypsum Cement

Exceptional Smoothness

Gypsum plaster offers a remarkably smooth finish, making it ideal for decorative coatings. The final surface is ready for painting or wallpapering without the need for additional smoothing or sanding.

Time Efficiency

As mentioned earlier, gypsum plaster sets quickly, a maximum of 3 days. This translates to faster construction progress, reducing labor costs and project timelines significantly. On the contrary, sand cement plaster needs about 20 to 28 days for curing.

Eco-Friendly

Gypsum is a naturally occurring mineral, making it an eco-friendly choice. It can be recycled, reducing environmental impact. Plus, it is non-VOC, thus, it provides VOC-free air. Moreover, it has a higher NRC value. 

Fire Resistance

Gypsum plaster is inherently fire-resistant, adding an extra layer of safety to your building. It can act as a barrier against the spread of flames, giving occupants more time to evacuate in case of a fire.

Higher Working Efficiency

Compared to cement plastering, gypsum plaster offers more working efficiency. It’s easy to handle and the cleaning process is comparatively easier than cement plastering.

Less Water Usage

For curing the cement plaster, water is mandatory. On the other hand, gypsum plaster doesn’t require that much water for curing, and water usage can be reduced by more than 90%. 

Quality Working Output

While using cement plastering, there is a chance of shrinkage on the surface. Sooner or later, you will have them on your wall. However, gypsum plastering prevents shrinkage cracks. Besides this, it provides a high-quality finish and also ensures undulation. 

Drawbacks of Gypsum Cement

While gypsum plaster offers numerous advantages, it’s essential to acknowledge its limitations

Moisture Sensitivity

Gypsum plaster is sensitive to moisture, and prolonged exposure to water can cause damage. It’s not suitable for areas with high humidity or frequent water contact. That’s why it’s only suitable for ceiling and interior walls. For the kitchen, bathroom, etc., using this won’t be a wise decision.

Cost

Although gypsum plaster can be cost-effective due to its quick drying time, it may be more expensive than traditional cement plaster in some regions.

Final Thoughts

In conclusion, gypsum’s role in cement plastering is nothing short of transformative. Its unique properties make it a valuable ally in the construction industry, offering benefits such as smooth finishes, time efficiency, and eco-friendliness. However, it’s crucial to consider its sensitivity to moisture and cost implications when deciding whether to opt for gypsum plastering. Ultimately, the choice between gypsum and traditional cement plaster depends on the specific requirements of your project.

Cementitious Mind Can Also Ask 

Is gypsum plaster suitable for exterior surfaces?

Gypsum plaster is primarily designed for interior surfaces. It is not recommended for exterior applications due to its sensitivity to moisture and weather conditions.

Can gypsum plaster be used for ornamental designs on walls?

Absolutely! Gypsum plaster’s exceptional smoothness and workability make it an excellent choice for creating intricate ornamental designs and decorative coatings.

Does gypsum plaster require any special curing process?

Unlike traditional cement plaster, gypsum plaster does not require a lengthy curing process. It sets rapidly, reducing the need for extended curing times.

Can gypsum plaster be applied over existing surfaces?

Yes, gypsum plaster can be applied over existing surfaces, provided they are clean, stable, and properly prepared. It offers a convenient option for renovating or refurbishing interior spaces.