key term - Calcium hydroxide

Definition

Calcium hydroxide, commonly known as slaked lime, is an inorganic compound with the formula Ca(OH)₂. It is a strong base and is crucial in the production of cement and concrete, where it contributes to the setting process and enhances the durability of concrete structures by improving its resistance to environmental factors.

5 Must Know Facts For Your Next Test

1. Calcium hydroxide is produced by adding water to calcium oxide (quicklime), resulting in an exothermic reaction that releases heat.
2. In the context of concrete, calcium hydroxide plays a vital role in the formation of calcium silicate hydrate (C-S-H), which is the main product responsible for strength development.
3. It helps improve the workability of concrete mixtures, allowing for better compaction and less water needed to achieve desired consistency.
4. Calcium hydroxide also acts as a filler in concrete, which can help reduce the permeability of concrete, enhancing its durability against moisture and chemical attack.
5. This compound can undergo carbonation in the presence of carbon dioxide, leading to the formation of calcium carbonate, which can affect the long-term strength and stability of concrete structures.

Review Questions

• How does calcium hydroxide contribute to the setting process of cement and concrete?
  • Calcium hydroxide is formed during the hydration process when water is added to cement. It reacts with silicates present in the cement to produce calcium silicate hydrate (C-S-H), which is crucial for gaining strength. The presence of calcium hydroxide not only supports this reaction but also improves the overall workability of the concrete mixture, making it easier to pour and shape.
• Discuss the environmental impact of calcium hydroxide in concrete applications, particularly regarding durability and resistance.
  • Calcium hydroxide significantly enhances the durability of concrete by reducing its permeability, which protects against moisture intrusion and chemical attacks. Its role in forming C-S-H ensures that the concrete remains structurally sound over time. Furthermore, as it undergoes carbonation, it can potentially increase the strength of concrete structures while also sequestering carbon dioxide from the atmosphere, contributing positively to sustainability efforts.
• Evaluate how understanding the properties of calcium hydroxide influences advancements in concrete technology.
  • Understanding calcium hydroxide's properties has led to advancements in concrete technology by enabling engineers to develop more efficient mixtures that enhance strength and longevity. Innovations such as incorporating supplementary cementitious materials or optimizing water-to-cement ratios are influenced by knowledge of how calcium hydroxide interacts during hydration. This understanding allows for tailored solutions that improve performance characteristics, reduce environmental impact, and extend the lifespan of concrete structures.

Related terms

Hydration: The chemical reaction that occurs when water is added to cement, causing it to harden and gain strength.

Portland Cement:

A type of cement made from a mixture of limestone and clay, which is ground into a fine powder and reacts with water to form a strong binding material.

Lime Cycle: The process of converting limestone into quicklime (CaO) and then slaked lime (Ca(OH)₂) by hydration, and finally returning it to limestone through carbonation.