AUTOCLAVED AERATED CONCRETE: AN ALTERNATIVE TO WOOD & PLASTIC
- Pritom Bhowmik
- Oct 3, 2020
- 6 min read
Updated: Jul 21, 2021
For about 70 years, Autoclaved Aerated Concrete (AAC), also known as aircrete, has been a green precast construction material. AAC blocks and AAC panels are produced in hundreds of plants worldwide; AAC is extensively used in residential, commercial, and industrial construction. AAC is a natural construction material formed from sand or fly ash, asphalt, lime, gypsum, aluminum powder, and water. This mixture produces aerated concrete, which provides insulation, structure, and fire safety in a single lightweight component. Aerated concrete is distinguished by the inclusion of huge voids that are purposefully included in the matrix to minimize density.
A Swedish architect blended the typical mixture of cement, lime, water, and sand with small quantities of aluminum powder During the 1920s. The aluminum powder acts as an expansion factor and causes concrete to expand in a similar way to bread dough. As a result, almost 80% of concrete is air. However, it was found that this technology was in use 800 years ago in our Indian subcontinent—a temple named Ramappa Temple, situated in the southern part of India. The temple roof was built with such material, which has similar properties to AAC. Since its modern invention in 1920, the basic properties of AAC have been changed a lot. Although the AAC is lightweight and perforated, it has now developed an efficient construction system that avoided some of its drawbacks, such as water absorption, maintenance costs. If you've ever wondered how to replace wood and plastic with these masonry ingredients, let's dive a little deeper into the features of this material.
AAC units are simple to assemble and can be cut and drilled with standard woodworking equipment such as band saws and power drills. The concrete must be examined for compressive qualities, moisture content, bulk density, and shrinkage because it is lightweight and low-density. In addition, it works as an excellent thermal insulator due to the closed, airtight pockets created by the mass's micro-bubbles. Due to its bubbled structure, it exhibits high resistance to liquid water penetration. As the closed pockets have practically null capillary suction, it lowers the water absorption rate of AAC. Furthermore, the bubbled nature provides substantial acoustic insulation benefit by reducing sound waves as they travel through the air pockets. According to several international guidelines, it has high fire resistance, one of the most critical metrics in the classifications of necessary resistance.
Usage of Wood That Can Be Replaced By AAC
Furniture Production
Home Construction
Arts & Craft
Fencing
Firing
Usage of Plastic That Can Be Replaced By AAC
Furniture
Shopping Cart
A significant portion of the wood is used for the production of furniture. As a replacement for wooden furniture, the usage of concrete has already started. The issue arises due to the heavyweight of regular concrete, but it's still underestimated. This is why we want to use AAC. As it is so light in weight, furniture made of it can be handled easily. Aircrete is already being used for the construction of houses, crafts, art & decoration purposes. Hence it is replacing woods. In many countries, wood is used for fencing & gardening, where AAC can be used much more effectively. Solid sphere shape concrete is already being used as fireballs in the fireplace and replacing woods. For the recent decade, Carbon Footprint (CF) assessment has been obligatory for any product or consumables due to sustainability issues. CF is commonly defined as the amount of equivalent carbon dioxide emitted into the environment because of the direct or indirect activities of a single person, organization, or community. According to the study, the carbon footprints of wooden furniture are somewhat high. Everything from the dining table to the stool is likely to have a higher carbon footprint, as the average piece of furniture uses around 47 kg of CO2e, which is equivalent to using 5.3 gallons of gasoline. So complete replacement of wooden furniture is a burning necessity.
Plastic has entered the market to reduce the tremendous need for wood, iron, and aluminum for different purposes and save the environment. However, the rest of the story is known to all; how overusing plastics is messing up everything. People throw the broken or used plastics after a certain period. 8.3 billion tons of plastic have been generated since 1950, with 6.3 billion tons ending up as waste, of which 79% has ended up in landfills and nature, 12% has been incinerated, and 9% has been recycled. 99% of plastics are produced from chemicals derived from oil, natural gas, and coal, which also have a greater deal of carbon footprint. The recycling rate is also shallow. AAC can be the best choice to replace plastic furniture, as it is eco-friendly & can sustain a much more extended period than plastics. It is also more reusable than plastics. Therefore, AAC can easily be molded to create different types of shopping carts to reduce the use of plastics to some extent.
Some significant disadvantages of wooden furniture and plastic furniture that AAC can overcome are given below:
Water: It causes swelling and staining, which eventually damages the wooden furniture. A special coating of AAC products can reduce these problems.
Humidity: Wooden products or furniture are prone to expand and contract due to temperature variation; the high thermal insulation properties of AAC can overrule this situation
Heat: Placing hot items on the wooden/plastic surface can damage it, not AAC.
Sharp objects: Different types of things like knives can create permanent deformation on the wooden and plastic product, which is not possible in AAC products.
Termites: Wooden furniture or products are often food for many parasites that destroys the product and create an unhealthy situation. Often these are overcome by chemicals, which are also harmful. AAC is handy in this case as it is termite-free naturally.
Fire: AAC products are highly fireproof, which is the opposite case for wooden or plastic furniture.
One of the most concerning flaws of AAC is its brittleness. This drawback of aircrete can be erased by the proper design and augmenting the study of the product. Researches have been conducted on mixing a variety of fiber in concrete to enhance its properties. Based on recent studies, adding fiber can reduce cracks by increasing impact resistance, concrete strength, and the elastic capacity of the concrete. Hence, adding fiber will increase its durability. So, usage of different types of fiber in the aircrete can also be a game-changing factor in this regard. The idea can be implemented in AAC, which will undoubtedly thrust it into the race with wood & plastic.
Moreover, it can be used further in replacing many other usages by adding respective ingredients. For example, we can give AAC a shape of a water bottle for a thought. However, we can only use it for carrying water by providing a barrier in the inner part to separate the water and AAC from not getting mixed. This idea could be huge potential in the future if properly utilized.
The plastic and wooden furniture industry is indeed growling rapidly in the global market. The trend is always in an upward direction. Lately, Sustainable development has been an in-demand issue all over the globe. Many countries have adopted SDG goals for sustainable outcomes. Consequently, researchers, thinkers, industrialists, and manufacturer companies are trying to be as green as possible in their production process and using as many bi-products as possible. So far, it is clear that wooden and plastic products are not sustainable.
In most cases, their production is higher carbon-intensive. The recycling rate is also shallow and has a high environmental impact. Nothing comes without flaws, but the ratio of supremacy has to be higher than the drawbacks, which is the case for AAC. Hence, replacing plastic & wooden products with AAC can be a far more effective deal as it is eco-friendly along with using bi-products like fly-ash and can be a sustainable solution for upcoming days.
References
6. Narayanan, N. and Ramamurthy, K., 2000. Structure and properties of aerated concrete: a review. Cement and Concrete Composites, 22(5), pp.321-329.
7. Qu, X. and Zhao, X., 2017. Previous and present investigations on the components, microstructure, and main properties of autoclaved aerated concrete – A review. Construction and Building Materials, 135, pp.505-516.ete Composites, 22(5), pp.321-329.
8. All the pictures are downloaded from different sources available on Google. The reference links have been hyperlinked with the respective images.
(This article was jointly developed with my teammate Pranjol Chakraborty to present on a couple of competitions)
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