AAC (Autoclaved Aerated Concrete) blocks are lightweight, durable, and highly insulating building materials. They are made from a mixture of sand, cement, lime, gypsum, and aluminum powder.
But only one specific type of lime is suitable and effective for AAC block production.
The lime used in AAC block manufacturing is High-Calcium Quick Lime (Calcium Oxide – CaO).
This quick lime reacts with water to form hydrated lime and plays a crucial role in the strength, expansion, and aeration of AAC blocks.
Quick lime used in AAC must be:
This ensures proper reaction with aluminum powder to generate air bubbles that make AAC blocks lightweight.
Quick lime (CaO) reacts with water → forms Ca(OH)₂.
This hydrated lime reacts with silica (sand) → forms C-S-H gel, the main binding material.
When aluminum powder is added, it reacts with lime to release hydrogen gas, forming tiny air bubbles.
These bubbles create the lightweight aerated structure of AAC blocks.
The blocks are then autoclaved (steam cured) for high strength.
Without proper quick lime, AAC blocks will not expand or gain strength correctly.
| Lime Type | Scientific Name | Used in AAC? | Purpose |
|---|---|---|---|
| High-Calcium Quick Lime (Correct) | Calcium Oxide (CaO) | ✔ Yes | Main reactive lime for aeration & strength |
| Hydrated Lime | Calcium Hydroxide (Ca(OH)₂) | ✔ Limited | Used when on-site slaking is not available |
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High-Calcium Quick Lime (Calcium Oxide – CaO).
Yes — only when high-quality hydrated lime is purchased ready-made. Quick lime is preferred.
It drives the chemical reaction that forms AAC structure and strength.
Yes — consistent lime quality ensures proper aeration and lightweight blocks.
High-calcium lime with 85–92% CaO is preferred.
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