AAC Block Industry
IS 712 certified Ultra Grade Ca(OH)₂ (93–95%) — the critical raw material for tobermorite formation in autoclaved aerated concrete blocks. Trusted by AAC block plants across India.
Autoclaved Aerated Concrete (AAC) blocks — the lightweight, thermally insulating building blocks replacing traditional red bricks across India — require high-purity hydrated lime (calcium hydroxide, Ca(OH)₂) as a key raw material. AAC block production has grown rapidly in India, driven by green building codes, energy efficiency requirements, and the superior performance of AAC over conventional bricks.
In the AAC manufacturing process, hydrated lime reacts with silica (fly ash or sand) and cement under high-pressure steam in an autoclave to form tobermorite — the calcium silicate hydrate mineral that gives AAC blocks their strength, low density, and thermal insulation properties. The purity of the hydrated lime directly determines the quality of this reaction and the final block properties.
Hydrated lime is one of the four key raw materials in AAC production: fly ash (or sand), cement, hydrated lime, and aluminium powder. The lime is mixed with fly ash, cement, water, and aluminium powder in precise proportions. The quality and consistency of the lime directly affects the mix design and the final block properties.
When aluminium powder is added to the lime-fly ash-cement slurry, it reacts with the calcium hydroxide to produce hydrogen gas. This gas creates millions of tiny air bubbles in the slurry, causing it to rise like bread dough. The Ca(OH)₂ content of the lime determines the rate and completeness of this reaction — insufficient or inconsistent lime leads to poor rising and non-uniform cell structure.
After cutting, the green AAC cake is cured in an autoclave at 180–200°C and 10–12 bar pressure for 8–12 hours. Under these conditions, Ca(OH)₂ reacts with silica from fly ash to form tobermorite (Ca₅Si₆O₁₆(OH)₂·4H₂O) — the mineral responsible for AAC's strength and low density. High-purity lime ensures complete tobermorite formation and consistent block strength.
The purity of hydrated lime affects both the density and compressive strength of AAC blocks. Impurities in the lime (MgO, SiO₂, Al₂O₃) can interfere with the autoclave reaction, producing blocks with inconsistent density, reduced strength, or surface defects. Ultra Grade lime with low impurity content is essential for producing AAC blocks that meet IS 2185 Part 3 specifications.
| Application | Recommended Grade |
|---|---|
| Standard AAC blocks (600–800 kg/m³) | Ultra (93–95%) |
| High-strength AAC blocks (800–1000 kg/m³) | Ultra (93–95%) |
| Low-density AAC panels (400–600 kg/m³) | Ultra (93–95%) |
| AAC blocks with fly ash (Class F) | Ultra (93–95%) |
Our Ultra Grade hydrated lime consistently achieves 93–95% Ca(OH)₂ content — the purity required for reliable tobermorite formation and consistent AAC block quality.
Low MgO (< 2%), low SiO₂, and low Al₂O₃ content ensures the autoclave reaction is not disrupted by impurities. Batch-wise test reports available for every shipment.
IS 712 fineness compliance ensures fast and complete dissolution in the AAC slurry. Fine lime reacts more completely with aluminium powder and fly ash silica.
Moisture content controlled below 2% (IS 712). Dry lime ensures accurate weighing, consistent mix design, and reliable aluminium reaction in the rising stage.
AAC block plants require uninterrupted lime supply. We maintain production capacity for monthly contracts of 50–300 MT with consistent delivery schedules.
IS 712 test certificates with every shipment. Supports your raw material quality documentation and IS 2185 Part 3 compliance for AAC block production.
Tell us your monthly requirement and plant location. We respond within 2 hours with a detailed price quote.