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ASTM C1452
Standard Specification for Reinforced Autoclaved Aerated Concrete Elements
Overview
ASTM C1452 covers prefabricated, steel-reinforced structural components made from autoclaved aerated concrete (AAC). AAC is a lightweight, cellular cementitious material produced from sand, lime, cement, water, and an expansion agent. The mixture is cast, cut into precise shapes, and cured under high-pressure steam in an autoclave, creating a strong, stable, lightweight calcium silicate hydrate matrix. The standard applies to both load-bearing and non-load-bearing reinforced elements for floors, roofs, walls, and stairs.
Material Properties
- Compressive strength classes from 2.9 to 8.7 MPa
- Dry unit weight: 320-800 kg/m³ (approximately 1/5 weight of concrete)
- High dimensional accuracy with strict tolerances
- Thermal conductivity: 0.08-0.16 W/(m·K)
- Must be protected from direct moisture exposure with approved coating
Consolidated Building Functions
The primary advantage is consolidation of multiple functions into a single component. An AAC wall panel provides structure, insulation, fire resistance, and acoustic barrier in one material. This simplifies design and detailing of the building envelope, reducing layers and trades required for construction. Large format and light weight significantly accelerate construction schedules compared to traditional block-by-block masonry.
Critical Moisture Management
AAC is porous and must be protected from direct water exposure. When AAC panels are used for exterior walls, design of the exterior cladding system is paramount. A robust, well-detailed weather-resistive barrier and cladding system must prevent bulk water from reaching the panels. Careful attention to flashing at openings and transitions ensures continuous moisture protection. While AAC isn't susceptible to rot or mold, prolonged saturation can affect insulating properties and interior finish performance.