A Beginner’s Guide to Autoclaved Aerated Concrete (AAC)
When it comes to the construction world, precast concrete plays a major role. It is very convenient to work with and affordable at the same time. This precast concrete is available in the form of precast blocks as well.
AAC is a widely used and easily available precast concrete form. In this article, we are going to discuss more AAC. So, without further ado, let’s jump to the introduction of AAC.
What is AAC?
Autoclaved Aerated Concrete refers to a type of precast concrete, which is available quite easily in the form of precast blocks. AAC has a smooth and homogenous nature due to the presence of a small aggregate. The base ingredients are fly ash, lime, cement, aggregate, and water. However, the density of the concrete can be adjusted according to the exact engineering specifications by adjusting the amount of aluminum powder used during the manufacturing process.
There are two shapes of AAC available, known as blocks and panels.
Properties of AAC concrete
Well, AAC has some magnificent properties. Here are some technical specifications of the AAC blocks, which you must always check before opting for them.
- Its density is 550-650 kg/m3 along with the comprehensive strength of 4 N/mm2 (Mpa)
- Shear strength is equal to 0.6 N/mm2
- The modulus of elasticity is 2040 Mpa.
- The moisture content at equilibrium state is 8% to 12%
- The coefficient of thermal expansion is 8.1 x 10-6 k-1 along with thermal conductivity f 0.24 w/m degree kelvin.
- Thermal resistance, i.e., R-value is equal to 0.46 m2 – 0k/w
- Drying shrinkage is 0.05 %, and fire resistance is 4 hours for a 200 mm wall.
- It possesses a sound transmission class rating of 44 decibels for a 200 mm wall.
Advantages of using Autoclaved Aerated Concrete
There are various perks of using AAC over other construction materials. Some of the important ones are mentioned below.
- It works perfectly as a soundproofing material and is also excellent for acoustic insulation on walls.
- It is a highly fire-resistant material
- The AAC blocks are available in a variety of sizes and shapes for versatile usage.
- These are recyclable.
- Convenient and easy shipping, handling, and installation
- It can be easily cut to make chases and holes for electrical and plumbing purposes.
- Affordable shipping and handling
Tools for AAC blocks masonry:
There are various tools, which are used for masonry. However, particularly for AAC blocks masonry, these seven tools are important.
- Mortar trowels
- Rubber hammer
- Level bottle
- Hand saw
- Grooving tool
Disadvantages of using AAC:
Just like every other construction material, autoclaved aerated concrete also has some drawbacks. The following are some of them.
- It is sometimes inconsistent in terms of color and quality.
- When the walls are unfinished, they need some protection. Hence, exterior cladding is used to protect the exterior walls from the weather.
- The R-value, i.e., the thermal resistance of AAC, is fairly low as compared to the energy-efficient insulated wall construction.
- The strength of AAC is comparatively low, which is 1/3 to 1/6 of traditional concrete blocks.
Tips to remember while storing the AAC concrete:
While storing AAC, these factors should be considered for achieving efficient results.
- Avoid water contact while storing the blocks.
- Avoid the usage of wet blocks during masonry. If by chance, the blocks become wet, it is important to dry them before use.
- Stack the blocks alternately to avoid corner chipping.
- If these AAC blocks are installed in an environment with high humidity, then make sure the interior walls have low vapor permeability and the exterior walls have higher permeability.
Tips for external plastering:
You must take these precautions to avoid unsatisfactory results of the external plastering of walls.
- Avoid the plastering of walls during the monsoon season. Do it after the walls are completely dry.
- The approximate width of the first coat of plaster should be 15 mm and the second layer of 5 to 10 mm thickness.
- Add Waterproofing chemicals to the plaster mixture.
How to avoid cracks?
Cracks can appear on the AAC walls at some corners because of the shear and tensile loading effect. So, it is always advised to add a nominal reinforced concrete bond beam at the lentil and sill level. Bond beam prevents shear stresses on the wall and hence, prevents the formation of cracks on the walls due to shear stress.
Recommended pre-work preparation:
Make sure you check these pre-work preparation points for better results.
- Use 100 mm (minimum) thick AAC blocks for internal walls. And for external walls, it must be 150-200 mm (minimum).
- If the thickness of the blocks is lesser than the recommended, then a suitable design change should be done.
- Making holes in block masonry for scaffolding support must be avoided. You should add Scaffolding support to concrete.
Thus, AAC has various advantages over other materials and works well for people with chemical sensitivities. Nowadays, most people are preferring to use AAC for building construction, and in the coming years, the prospects for AAC concrete will get better.
If you are looking for a well-established company that provides excellent quality precast concrete material, you must check out Magicrete Precast. They offer premium precast materials, which will give efficient and fruitful results.