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Hydrated Lime: A Noteworthy Material Empowering The World

Glancing at hydrated lime, a powering mineral


As we continuously strive to safeguard our environment, the search for efficient and sustainable solutions to diverse challenges remains paramount. One noteworthy solution garnering increasing interest is the utilization of hydrated lime within environmental treatment processes. Hydrated lime stands as an adaptable and eco-conscious material, providing a multitude of advantages to our natural world.

This blog post delves into this mineral, examining several essential elements that influence human life.

What Is Hydrated Lime?

With the chemical formula Ca(OH)2 also known as calcium hydroxide, it is a powerful alkaline substance created when calcium oxide combines with water. An interesting aspect of this reaction is that it produces heat. The amount of water used during the process influences the final form of calcium hydroxide, which can range from a dry powder (dry hydrate) to a paste-like consistency (putty lime), or a liquid suspension known as milk of lime or lime slurry.

The Physical Properties

Calcium hydroxide is a solid, white or slightly beige powder with a crystalline structure. Despite being slightly soluble in water, it’s also hygroscopic, meaning it actively draws moisture from the surrounding air. This can cause the powder to clump or cake over time.

Hydrated lime is a powerful alkaline substance
A crystalline structure of Calcium hydroxide

Although not flammable, calcium hydroxide is caustic, so it’s important to handle it carefully.

The Manufacturing Process

Hydrated lime is produced through a process called “slaking,” where calcium oxide (quicklime) is combined with water. Hydrated lime, sometimes referred to as slack lime, builders lime, or pickling lime, has a wide range of industrial applications. It’s used in the creation of mortars, plasters, cement, paints, and hard rubber products. Additionally, it plays a role in petrochemical processes and the tanning of leather.

The Wide Range Of Uses Through Different Sectors

Hydrated lime finds widespread use in various industrial applications. These include chemical manufacturing, water and wastewater treatment, acid neutralization, and a variety of other environmental protection processes.

In history, hydrated lime, along with other lime-based products, boasts a long and rich history of agricultural and non-agricultural applications. While its use as a pesticide ingredient has largely been discontinued, its effectiveness as an external parasiticide in organic livestock production remains recognized. In this day and age, it is applied in various sectors. The lists are below:

Water waste treatment

A significant application of this mineral lies in water treatment. It effectively adjusts water pH levels, counteracting acidity. Additionally, it removes impurities like heavy metals, fluoride, and organic pollutants. Being naturally alkaline, it acts as a powerful coagulating agent, helping to settle suspended particles in water. Water treatment facilities rely on hydrated lime to purify both drinking water and wastewater.

Steel manufacturing

Hydrated lime plays a vital role in several aspects of the steel industry. In plants where coke is a by-product, it neutralizes impurities. Steel plates are frequently given a hydrated lime coating, creating a short-term protective layer against oxygen-based corrosion.

Crucially, hydrated lime serves as a fluxing agent during the steel production process itself.  It reacts with silica and alumina impurities in iron ore, transforming them into slag. This slag floats on the molten iron, allowing for easy removal. Employing hydrated lime in steel production also leads to greater efficiency, reducing both energy and raw material consumption.

Chemical manufacturing

Hydrated lime serves as a fundamental building block in the manufacturing of numerous chemicals, including bromide, caustic soda, fluoride, magnesia, lactate, nitrate, oleate, and stearate.  It’s also essential in the creation of various calcium salts, both organic and inorganic, such as calcium carbide, calcium hypochlorite, calcium magnesium acetate, and calcium phosphate. Additionally, this kind of mineral contributes significantly to the purification process of citric acid.

Flue gas treatment

Hydrated lime acts as a catalyst in neutralizing harmful emissions from cement plants, coal-fired power plants, glass manufacturing facilities, and other industries involving combustion. Its anions readily capture acidic pollutants typically released into the atmosphere – like hydrogen fluoride, hydrogen chloride, sulfur dioxide, selenium, and fine particulate matter. This reaction effectively converts these pollutants into calcium sulfate, a less harmful substance.

hydrated lime through various applications
Along with other lime-based products, boasting a long and rich history through various applications

Sugar production

Hydrated lime plays a crucial role in sugar production, whether sourced from cane or beets. It interacts with impurities and raises the pH level, facilitating their removal.  Additionally, hydrated lime assists in purifying maple syrup, sorghum, and other viscous sugar varieties.  Before final packaging, a carbonation process eliminates any excess lime from the product.

Acid reduction

During the separation of cream from milk, hydrated lime is added to reduce the cream’s acidity before the butter-making process. Additionally, lime added to the remaining milk can lead to the production of either lactic acid (when combined with a low-pH chemical) or calcium lactate, the latter being a valuable ingredient in medicinal supplements.

Masonry binding

Hydrated lime has widespread use in construction. It binds with sand to create plaster and stucco. When added to cement (at around 15%), it notably reduces shrinkage and cracking. Additionally, hydrated lime plays an important role in stabilizing the foundations of roads, buildings, dams, and airfields.

Paint formation

Limewash paint is created by combining hydrated lime, water, and pigment to form a paste. This mixture is then applied to create the characteristic limewash effect.


Hydrated lime finds extensive use as a construction material due to its positive impact on workability and durability.  It’s commonly found in mortar and plaster, where it reacts with other ingredients to form calcium silicates and calcium aluminates. These compounds boost the mix’s strength and adhesion. Additionally, hydrated lime’s natural ability to inhibit mold and mildew growth makes it particularly valuable for construction in humid areas.

What Is The Difference Between Quicklime And Hydrated Lime?

Quicklime (calcium oxide, CaO) and hydrated lime (calcium hydroxide, Ca(OH)2) are closely related but differ in their chemical composition. This leads to variations in properties and uses:

  • Chemical Formula: Quicklime (CaO) vs. Hydrated Lime (Ca(OH)2)
  • Molar Mass: Quicklime (56.07 g/mol) is lighter than Hydrated Lime (74.09 g/mol)
  • Melting/Boiling Points: Quicklime has significantly higher melting and boiling points (2,613°C and 2,850°C) compared to hydrated lime (which melts at 580°C and decomposes upon further heating).


  • Quicklime: Used in steelmaking, production of aerated concrete blocks, glass manufacturing, and organic chemical synthesis.
  • Hydrated Lime: Employed for treating flue gas and neutralizing industrial wastewater.

Looking in  more details about Quicklime

The Chemical Risks That You Should Know

Unlike thermal burns caused by heat transfer, chemical burns involve a deeper process. They occur due to a direct reaction between the chemical and the body tissues it comes into contact with, such as skin, eyes, or mucous membranes. This reaction can be categorized as acid-base, oxidation-reduction (redox), or other chemical interactions. In the case of lime, for example, the reaction is an acid-base interaction.

The 3-Step Process of Chemical Burn Formation:

  • Contact: The chemical substance comes into direct contact with the body tissue.
  • Diffusion: The chemical agent penetrates deeper into the tissue layers.
  • Reaction: The chemical reacts with biological compounds within the affected tissue, causing damage.

The severity of a lime-related injury depends on factors like the type of lime, its concentration, temperature, and the duration of contact with the skin, eyes, or mucous membranes. Regardless of the specific form, lime is a hazardous substance due to its irritating and corrosive properties. Its widespread use increases the danger, with the potential for serious burns to the eyes, skin, and respiratory system. Exposure can occur through solid, dust, or solution forms of lime.

Contact with the eyes

Exposure of the eyes to quicklime or hydrated lime can lead to various consequences, ranging from mild irritation to severe chemical burns.  These burns can potentially cause permanent vision loss (blindness).  The powdery form of lime is particularly dangerous, as moisture in the eyes can worsen the reaction and increase the burn’s severity.

Skin contact

Lime exposure can cause burns that might not hurt right away, leading to serious injuries before you even realize there’s a problem. These burns can be minor or severe enough to need a doctor

In Conclusion

Hydrated lime is a remarkably versatile chemical with a wide range of uses across industries. It’s great for improving performance, making processes more efficient, and boosting sustainability. As different sectors of the economy keep changing, it is likely to become even more important, helping us tackle new challenges around the world.


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