AIRCRETE lightweight concrete | Everything you need to know

September 13, 2021

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Autoclaved aerated concrete AAC, Aerated Cellular Concrete ACC, Autoclaved Lightweight Concrete ALC. This precast, porous, foam concrete building material goes by many different names.

Ingredients

AAC primarily consists of cement, lime, gypsum anhydrite, finely ground sand or fly ash, aluminum powder, and water. The chemical reactions between these components lead to the formation of AAC blocks. Steam curing in an autoclave allows the concrete to retain its porous structure and harden in just 8-12 hours, much faster than traditional air curing methods.

Benefits and Applications

AAC boasts numerous advantages. Being 80% air, it is significantly lighter than regular concrete with a low density of 300 kg/m3 or 20 pounds/ft3. Its lightweight nature reduces transportation and labor costs, while also speeding up assembly time on-site. Additionally, AAC demonstrates excellent dimensional stability despite its porosity, making it suitable for various construction applications.

AAC’s closed cellular structure and high thermal mass contribute to its exceptional insulation properties. An 8-inch thick AAC wall provides insulation comparable to a 2×6 wood stud frame wall with R20 fiberglass batt insulation or an 8-inch CMU block wall with R8.6 rigid insulation. The material can offer up to 35% energy savings in both hot and cold climates. However, to comply with building codes, additional continuous insulation may be required.

Moreover, AAC possesses remarkable fire resistance, withstanding exposure to fire for up to 4 hours without charring or losing structural integrity. It is also an excellent acoustic insulation material, capable of reducing sound transmission between rooms and from the exterior to the interior.

Challenges and Environmental Impact

While AAC presents several advantages, it does have some drawbacks. Its strength is around 1/6 to 1/3 of traditional concrete, making it less suitable for certain structural applications. Additionally, it requires special care during handling and transportation due to its brittleness.

From an environmental perspective, AAC is considered eco-friendly, being recyclable, non-toxic, and long-lasting. However, the autoclaving process demands significant energy and water resources, requiring a careful evaluation of its overall environmental impact.

Future Outlook

Though popular in Europe and Asia, AAC has faced challenges gaining traction in North America. Cost considerations and the dominance of stick building have been hurdles to its widespread adoption. However, recent spikes in lumber prices, natural disasters, and environmental concerns are driving the industry to explore more sustainable alternatives like AAC.

The demand for AAC is steadily rising, and manufacturers are investing in new facilities to cater to the North American market. Hebel, one of the prominent AAC manufacturers, is set to open a new factory in the United States, which will reduce transportation costs and boost its accessibility.

Conclusion

AAC offers a promising solution to the construction industry’s quest for sustainable building materials. Its unique properties, including lightweight, insulation, and fire resistance, make it an attractive choice for various applications. With increased awareness of environmental impacts and the search for better alternatives, AAC is poised to witness significant growth in the North American market and beyond. Embracing AAC not only reduces construction costs and enhances energy efficiency but also contributes to a greener and more sustainable built environment.