Autoclaved Aerated Concrete (AAC) block is a low-maintenance precast building material with excellent thermal insulation and durability.
1. Raw Materials and Production Process
Autoclaved Aerated Concrete (AAC) Blocks
Raw Materials: Silica-based materials (fly ash, sand), calcium-based materials (lime, cement), aluminum powder (foaming agent), and water.
Production: Cured in autoclaves under high-temperature and high-pressure conditions (180–200°C, 8–12 bar) to create a closed-cell porous structure via hydrogen gas release.
Key Feature: Uniform, stable closed-cell pores.
Non-Autoclaved Lightweight Blocks
Raw Materials: Cement, aggregates (slag, ceramsite, crushed bricks), and optional foaming agents (e.g., hydrogen peroxide) or lightweight fillers.
Production: Cured naturally or with low-pressure steam, relying on chemical reactions or physical foaming to form pores.
Key Feature: Simpler process and lower energy consumption, but pores may be uneven.
| Property | AAC Blocks | Non-Autoclaved Blocks |
|---|---|---|
| Density | Lower (400–800 kg/m³) | Higher (600–1200 kg/m³) |
| Compressive Strength | Higher (3.5–7.5 MPa) | Lower (2.5–5 MPa) |
| Thermal Insulation | Superior (λ = 0.1–0.2 W/m·K) | Moderate (λ = 0.2–0.35 W/m·K) |
| Water Absorption | Low (≤15%) due to closed-cell structure | High (may exceed 30%), requires surface treatment |
| Durability | Excellent (high frost/weather resistance) | Prone to shrinkage cracks, lower long-term stability |
| Fire Resistance | Non-combustible (Class A, high fire rating) | Class A achievable but lower performance |
Production Cost:
AAC: Higher initial investment and energy consumption (autoclaving), but highly industrialized.
Non-Autoclaved: Lower energy use and simpler equipment, suitable for small-scale production.
Construction:
AAC: Lightweight, easy to cut, requires specialized adhesives.
Non-Autoclaved: Heavier, often uses conventional mortar, slower construction.
AAC Blocks:
High-rise buildings (partition walls, insulated facades, fire-rated walls).
Projects prioritizing lightweight design, thermal/acoustic insulation.
Non-Autoclaved Blocks:
Low-rise buildings, rural housing, temporary structures.
Cost-sensitive projects with lower performance requirements.
AAC: Utilizes industrial waste (e.g., fly ash) but energy-intensive production.
Non-Autoclaved: May incorporate recycled aggregates (e.g., construction waste) but lower durability limits reuse.
AAC Blocks: Premium performance for high-standard projects.
Non-Autoclaved Blocks: Economical choice for basic applications.
Selection depends on budget, performance needs, and long-term durability requirements.
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