What is Quicklime and How is it Used?

Introduction

Quicklime, also known as calcium oxide, is a widely used inorganic compound produced from limestone. It is commonly used in construction, agriculture, and industrial processing due to its strong alkaline nature and high reactivity.

In this guide, we explain what quick lime is, how it is made, and where it is typically used.

What is Quicklime?

Quicklime calcium oxide is produced by heating calcium carbonate materials such as limestone at high temperatures. This process, known as calcination, removes carbon dioxide and leaves behind calcium oxide.

This material is sometimes referred to as burnt lime, reflecting the thermal process used in its production. The resulting compound is dry, caustic, and highly reactive, particularly when exposed to moisture.

Quicklime differs from hydrated lime. When calcium oxide reacts with water, it forms calcium hydroxide, which has different handling and application characteristics.

How Quicklime is Made

The production of calcium oxide quicklime begins with limestone. When heated to temperatures above 900°C, the calcium carbonate breaks down into calcium oxide and carbon dioxide gas.

This process significantly alters the chemical behaviour of the material. While limestone remains relatively stable, quicklime becomes reactive and capable of generating heat when combined with water.

Key Properties

Quicklime is strongly alkaline and reacts readily with water in an exothermic reaction. This release of heat is a defining feature of calcium oxide.

It is also hygroscopic, meaning it absorbs moisture and carbon dioxide from the air. Over time, exposure to air will gradually convert it back into calcium carbonate.

These properties influence how it is stored, handled, and applied across different industries.

Where It Is Used

Construction

Quicklime is used in soil stabilisation and ground improvement. It reacts with moisture in soils to improve strength and reduce plasticity.

Agriculture

Quicklime is applied to soils to adjust pH levels. It helps reduce acidity and supports nutrient availability in agricultural settings.

Water Treatment

Calcium oxide is used to adjust pH and assist in the removal of impurities in water and wastewater treatment systems.

Industrial Processing

In industries such as steel manufacturing, burnt lime is used to remove impurities during refining processes.

Quicklime vs Limestone

Quick limestone is often confused with quicklime, though they are not the same. Limestone is calcium carbonate, a stable material used in construction and aggregates.

Quicklime is the processed form of limestone. The calcination process changes its chemical structure, making it significantly more reactive.

How to Handle Quicklime

Store in dry conditions to prevent unwanted reactions with moisture.
Avoid direct contact with skin and eyes due to its corrosive nature.
Use appropriate protective equipment when handling powders or granules.
Keep containers sealed to limit exposure to air and humidity.

Safety Considerations

Quicklime reacts with water and can release heat rapidly, which may cause burns. Dust should not be inhaled, and handling should take place in controlled conditions.

Proper storage and handling procedures are essential to maintain safety and material stability.