All About Gypsum in Construction

According to statistics from the construction industry, the UK uses around 4 million tonnes of gypsum each year. This comes from domestic production as well as net imports. The UK does have natural gypsum but it also manufactures a synthetic version of it too. This level is increasing in Great Britain. In 2022, the value of new work construction increased to a record high. The increase was 15.8%, which amounted to almost £133,000 million. The growth in 2022 was driven by private and public sector growth alike. 

What is gypsum?

Gypsum is a hydrated form of calcium sulphate, otherwise called calcium sulphate dihydrate. It is a soft sulphate mineral with the chemical formula CaSO4.2H2O. This means it is made up of water, oxygen, sulphur and calcium. The substance is used widely as the main constituent in lots of forms of plaster, chalk (for blackboards or pavements), drywall and fertiliser. 

Naturally, gypsum is created due to seawater evaporation. It occurs as nodular masses or as beds that can be several metres thick. It occurs within layers of sedimentary rock. Gypsum, as opposed to anhydrite, which is the anhydrous form of calcium sulphate, forms near the surface. Typically, when you get to 40 to 50 metres below the surface, you get anhydrite instead. 

Gypsum occurs naturally around the world and is mined in places like Thailand, Brazil, Russia, the US and the UK. The substance is soft and white or grey in colour and is extracted with surface mining. After extraction, it is crushed inside industrial machines and then sorted into pieces of different sizes depending on their intended commercial use. 

Synthetic gypsum is often produced as a by-product in some industrial processes. This includes the FGD (flue gas desulphurisation) process. This is purer (around 96%) compared to natural gypsum, which is about 80% pure usually.

What are the types of gypsum in construction?

Gypsum is widely used in construction and for many different reasons. Generally, it is used to improve the structural properties of a building. Here are some examples:

• It is resistant to heat, moisture and fire.
• It absorbs sound.
• It is strong, durable and resistant to cracking.
• It sets and hardens quickly.

The construction industry generally uses gypsum in powder form. When it is heated in its natural solid form, it loses its water molecules and becomes a powder. This is known as plaster in the construction industry. Applying different amounts of heat to the gypsum will give you different types of plaster. 

By adding water to gypsum powder, it will set and turn solid once more. This means it can be easily moulded and smoothed for surfaces. 

When it is ground and heated to between 150°C and 165°C around 75% of its water is removed. This product is known as plaster of Paris.

How is gypsum used in construction?

Gypsum’s properties mean it is an especially useful product in construction. It has been used in construction for centuries. Ancient civilisations used alabaster, which is gypsum in solid form, to make sculptures. Powdered gypsum was also used to construct the pyramids of Giza.

Here are some of the ways it is used in construction these days:

Plasterboard

This also goes by the name of gypsum board and drywall. It has a gypsum core that is sandwiched between two facers, which is essentially thick paper. The core will often contain other additives that improve its structure. 

Plasterboard has excellent soundproofing and fire-resistant properties. It is also light, cheap and easy to install. Plasterboard’s main uses are in interior wall structures and ceilings. The majority of UK residential and commercial properties will contain gypsum in this form.

Synthetic gypsum is used widely in the manufacturing of plasterboard. Demand for gypsum is heavily driven by plasterboard manufacturing.

Decorative plaster

Gypsum in the form of plaster of Paris is used for casts, models and moulds for decorating in construction. This is also crack- and shrink-resistant when it’s dry—and it dries quickly too. 

Gypsum fibreboard

This is like plasterboard. It is used to line roofs, floors, ceilings and walls. It is shock-resistant and also resistant to humidity. Fibreboard is also good for soundproofing. 

Building plaster

This is the plaster that you use to skim walls and ceilings. It is easy to use and will set quickly. Natural gypsum is favoured for building plaster because it contains natural clays that make it more workable.

Self-levelling screed

Gypsum-based screed is used for floors in buildings as it is self-levelling. It is strong and thermally stable. 

Concrete

When you add gypsum to cement, it does increase how long it takes to harden and dry. However, the concrete is more stable. 

Plaster block

These tiles are used to make building partitions and ceilings. They are fire-resistant.

Why is gypsum used in construction?

Gypsum has many features that make it useful for building. It contains crystal water and is non-combustible. This means it can stop fires from spreading within buildings. It also has low thermal conductivity, which means it can keep heat within rooms, lowering bills. 

Besides its fire-resistant properties, gypsum offers soundproofing. When plasterboard is used, there is an additional sound barrier in the room. What’s more, it is impact-resistant. This means that it can be used in places where strong walls are needed like corridors in busy buildings like hospitals or schools. 

Another thing that’s great about this material is that it’s sustainable and can be recycled. It is easy to use but also easy to disassemble. 

In many applications, gypsum replaced asbestos as a safer alternative. It has now substituted the use of asbestos in many construction materials where non-toxic and fire-resistant products are needed. For instance, plasterboard, fireproofing, insulation and ceiling tiles would have once been manufactured using asbestos but have now been replaced with gypsum. 

Do gypsum products contain asbestos?

No. Gypsum products do not contain asbestos. However, the Health and Safety Executive does say that when gypsum-based plasterboard is used and its dust becomes airborne, its dust could contain fibres of asbestos. As such, some people wrongly believe gypsum contains asbestos.

Back in the 1930s, both asbestos and gypsum were gaining in popularity as building materials. No one realised just how terrible asbestos was for health, nor the dangers that came with ingesting it or inhaling its fibres. Asbestos was simply thought of as useful for insulating and strengthening building work. It also had soundproofing properties and was heat-resistant.

Nowadays, plasterboard doesn’t contain asbestos but it used to. As such, buildings constructed between the 1930s and 1990s might have plasterboard that contains asbestos. However, when asbestos-containing plasterboard is painted, the fibres are sealed inside. Therefore, the risk of harm is reduced significantly. But, if the plasterboard is disturbed, the fibres can become dangerous as they could become airborne. 

The construction industry commonly recycles old plasterboard for environmental reasons. However, this now needs to be tested for asbestos because it is illegal to use asbestos in building materials nowadays. 

What is the difference between gypsum and asbestos?

Gypsum and asbestos, though they share similar properties, are distinct materials that have different compositions.

Firstly, gypsum is a soft sulphate material that’s found in formations of sedimentary rocks. Asbestos, on the other hand, is a naturally occurring mineral (or a group of such minerals) that are thin, fibrous crystals. Types of asbestos include tremolite, actinolite, anthophyllite, crocidolite, amosite and chrysotile. 

The physical properties of the two also differ. Gypsum is soft. It has a Mohs hardness score of 2. This means it can be scratched easily with a fingernail. It is not fibrous and isn’t as heat-resistant as asbestos. Asbestos is fibrous and is much better than gypsum at retaining heat and insulating. It is resistant to fire, corrosion by chemicals and electricity. 

Both products have been used in the construction industry, though asbestos is now banned due to its association with serious health problems like lung diseases and cancer. Asbestos was used commonly in fireproofing materials and insulation due to its properties. Gypsum isn’t best known for these properties but it also doesn’t have hidden dangers like cancer, specifically mesothelioma.

Comparatively, gypsum is considered safe to use in construction. It poses minimal risks to health. Asbestos has been outlawed since 1999 due to its health risks. 

Can gypsum cause harm?

Although gypsum doesn’t contain asbestos, some building materials could have been contaminated with asbestos if they were made before the use of asbestos was made illegal in 1999. In these cases, it is the asbestos fibres and not the gypsum that is a risk to your health. 

Asbestos is the biggest causal factor of occupational disease in the construction industry, despite the product being illegal for over 20 years. However, because many buildings still contain older materials, construction workers need to take particular care when working.

Gypsum itself is non-toxic. However, any dust that is inhaled or ingested on a regular basis can cause harm. Workers will use gypsum with control measures in place. The Control of Substances Hazardous to Health (COSHH) Regulations outline the limits of how much dust workers can be exposed to. PPE should be worn, for example.

Is there an environmental impact of using gypsum in the construction industry?

Understanding the environmental impact of gypsum is important as we seek to promote sustainable building practices.

The material is sourced primarily from mining in a range of regions worldwide. Its extraction involves surface mining, which means we need to consider the environmental impact. Land rehabilitation, sustainable mining practices and adherence to environmental regulations are essential to responsible gypsum sourcing. 

When synthetic gypsum is produced, it is actually a by-product of other processes. This means that it reduces waste produced in industry by repurposing something that otherwise would go to landfill. 

Reusability of gypsum

Thankfully, gypsum has noteworthy recyclability. The construction industry recycles gypsum-based materials commonly, which reduces the demand for raw materials and minimises waste. It is common practice to recycle old plasterboard, although this does require testing for asbestos and asbestos contamination before it can be used again. 

Gypsum is sustainable

Gypsum is inherently sustainable. This is because it is non-combustible and is a fire inhibitor. Its low thermal conductivity also means that it helps rooms to retain heat, which contributes to lower heating bills and energy efficiency. Its soundproofing qualities also mean it offers acoustic insulation. 

The advantages and disadvantages of using gypsum in the construction industry

As we’ve seen, gypsum is popular as a building material in the construction industry. Let’s look at its advantages and disadvantages together:

Advantages of gypsum

• It is fire-resistant, which makes it an ideal choice for applications where fire safety is important.
• It has excellent sound absorption properties. This makes it a preferred choice for places where noise control is crucial.
• It is highly workable. It is smoothed and moulded easily from its powder form, which makes it versatile for using in plastering and casts.
• It is recyclable.
• It has low thermal conductivity. This helps rooms to retain heat, making them more energy efficient and cheaper to keep warm.
• Synthetic gypsum is a by-product of other industrial practices, making it a sustainable product.

Disadvantages of gypsum

• It is sensitive to moisture. Prolonged exposure can compromise the structural integrity of the product.
• Though it is strong and durable, it doesn’t have high structural strength.
• Its extraction has environmental implications.

Final thoughts on gypsum in the construction industry

Gypsum, whether natural or synthetic, is commonly preferred for interior construction like walls and ceilings. Its sound absorption, fire resistance and workability mean it is great for both residential and commercial purposes. It is also a sustainable product, provided that natural gypsum is mined considerately. However, it is not the best material for heavy industrial applications or for moist environments. In these cases, cement board or plastics might be better. Importantly, gypsum isn’t dangerous to health like asbestos. However, care should still be taken when demolishing old walls with plasterboard as asbestos wasn’t banned until 1999.