Builders have been using lime in construction for centuries. Hydrated lime is a versatile material used in various construction applications. It is made by adding water to quicklime, which is produced by heating limestone in a kiln. The result is a fine white powder that is used extensively in construction.
One of construction’s most common uses of hydrated lime is as a mortar additive. It is added to cement and sand to create a workable and durable mortar that can be used to bond bricks and stones together.
Hydrated lime mortar is preferred over more modern cement mortar as it is more flexible and breathable, allowing moisture to escape from the walls. This helps to prevent damp and mould from forming, which can be a significant problem in older buildings.
What is Hydrated Lime?
Hydrated lime, also known as calcium hydroxide, is a fine white powder that is made by adding water to quicklime. Quicklime is produced by heating limestone to a high temperature until it undergoes a chemical change, releasing carbon dioxide and leaving behind calcium oxide. When water is added to calcium oxide, it reacts to form calcium hydroxide or hydrated lime.
Hydrated lime has many uses in the building industry, including as a mortar additive, soil stabiliser, and in the production of lime mortar, plaster and stucco. It is also used in water treatment, food production, and as a pH adjuster for soil and industrial processes.
Hydrated lime is sold in different grades, each with varying levels of purity and particle size. The type of hydrated lime used depends on the specific project requirements.
Related article: Hydrated Lime vs Hydraulic Lime: What Are The Differences?
Uses of Hydrated Lime
Building and Construction
Builders use hydrated lime in a variety of ways in construction. It is commonly used as a mortar additive to improve the workability and durability of the mortar. Hydrated lime can also be used to make plastering materials for walls and ceilings and as a flooring material. It can also be used as a stabiliser for soil and as a binder for bricks and blocks as mortar.
Agriculture
Hydrated lime is used in agriculture to neutralise soil acidity and raise pH levels. It can also be used as a disinfectant for animal feed and as an additive in some pesticides. In addition, hydrated lime can be used to treat livestock waste and control odours.
Water Treatment
Hydrated lime is used in water treatment to remove impurities and adjust pH levels. It can also be used to soften water and control the growth of algae and bacteria.
Chemical Manufacturing
Hydrated lime is used in chemical manufacturing to produce various products, including calcium stearate, calcium hypochlorite, and calcium phosphate. It can also be used to produce rubber products, petrochemicals, and tanning leather.
Overall, hydrated lime is a versatile material that is widely used in a variety of industries. Its unique properties make it an ideal material for many applications, from construction to agriculture to water treatment and beyond.
Hydrated Lime Powder VS Hydrated Lime Putty (fat lime)
Builders use hydrated lime powder and hydrated lime putty (fat lime) for different purposes. The main differences between these two forms of hydrated lime lie in their composition, consistency, and properties.
Hydrated lime powder is a dry, white, powdery substance that is made by adding water to quicklime (calcium oxide) in a large enough quantity to cause the quicklime to react fully but not turn into a wet paste. It is commonly used as an additive in cement, mortar, and plaster to improve workability, durability, and water resistance. It is also used in soil stabilisation, water treatment, and industrial processes.
Hydrated lime powder is an inferior type of lime when compared to putty. This means it shouldn’t be used on its own to make lime mortars and plasters. Builder’s lime is best used with cement to help add workability and durability to the mortar or plaster.
Hydrated lime putty (fat lime), on the other hand, is a wet, creamy, paste-like substance that is made by slaking quicklime with water and allowing it to mature for several months. It is commonly used as a binder in traditional lime mortars, plasters, and renders for historic buildings and conservation projects. It is also used in natural building, earthen construction, and artistic applications.
Related article: Fat Lime in Construction: Uses, Advantages, and Limitations
The following table summarises the main differences between hydrated lime powder and hydrated lime putty:
| Property | Hydrated Lime Powder | Hydrated Lime Putty (fat lime) |
|---|---|---|
| Composition | Calcium hydroxide (Ca(OH)2) | Calcium hydroxide (Ca(OH)2) + free water (H2O) |
| Consistency | Dry powder | Wet paste |
| Application | Additive in cement, mortar, plaster, soil stabilization, water treatment, and industrial processes | It provides good breathability, flexibility, and self-healing |
| Properties | Improves workability, durability, and water resistance | Provides good breathability, flexibility, and self-healing |
It is important to note that hydrated lime putty (fat lime) is not interchangeable with hydrated lime powder in lime mortars, plasters, and renders. Using the wrong type of lime can lead to cracking, spalling, and other damage to historic buildings and structures. Builders should always consult with a conservation professional or a lime expert before using lime products in conservation projects.
Properties of Hydrated Lime
Hydrated lime has several properties that make it useful in various applications. One of its most important properties is its ability to react with acids. When hydrated lime is added to an acidic solution, it neutralises the acid and raises the pH. This makes it useful as a pH adjuster in various industries, including agriculture, water treatment, and construction.
Another important property of hydrated lime is its ability to absorb moisture. This makes it useful as a desiccant or drying agent. It can be used to dry out wet soil or to absorb moisture in the air. In addition, hydrated lime is non-toxic and non-flammable, making it a safe and easy-to-handle material.
Overall, hydrated lime is a versatile and useful material that has a wide range of applications in various industries. Its unique properties make it an essential component in many products and processes, including cement, mortar, and plaster, as well as in agriculture and water treatment.
Benefits of Using Hydrated Lime
Builders use hydrated lime for various reasons, and it has several benefits. Here are some of the benefits of using hydrated lime:
- Improves workability: Hydrated lime acts as a plasticiser, which makes the mortar more workable and easier to spread.
- Increases durability: Lime mortar has excellent water resistance and can withstand freeze-thaw cycles. It also has a self-healing property, meaning it can repair itself if small cracks appear.
- Reduces shrinkage: Hydrated lime reduces the shrinkage of mortar as it dries, which helps to prevent cracking.
- Improves bond strength: Lime mortar has excellent adhesion to masonry units, which helps to improve the bond strength between the units and the mortar.
- Improves breathability: Lime mortar is porous, which allows moisture to escape from the wall. This helps to prevent moisture damage and improves the overall health of the building.
- Improves appearance: Lime mortar has a beautiful, natural appearance that complements historic buildings and traditional construction methods.
Overall, hydrated lime is an excellent choice for builders who want to create durable, long-lasting, and beautiful buildings. Its unique properties make it ideal for use in historic restoration projects, as well as new construction.
Precautions When Using Hydrated Lime
Hydrated lime is a caustic material that can cause skin irritation, respiratory problems, and eye damage. Therefore, taking the necessary precautions when using hydrated lime is crucial.
Here are some safety measures that builders should take when handling hydrated lime:
- Wear protective clothing, including gloves, a dust mask, goggles, and a long-sleeved shirt and pants.
- Avoid inhaling the dust by using a respirator or mask designed for lime dust.
- Avoid getting hydrated lime on the skin, as it can cause chemical burns. If it does come into contact with the skin, wash the affected area with water immediately.
- If hydrated lime gets into the eyes, immediately flush them with water for at least 15 minutes and seek medical attention.
- Store hydrated lime in a cool, dry, and well-ventilated area away from incompatible materials.
- Do not mix hydrated lime with other chemicals unless specifically directed to do so.
- Follow the manufacturer’s instructions and read the safety data sheet before using hydrated lime.
By taking these precautions, builders can safely handle hydrated lime and avoid any potential hazards associated with its use.
