Real Estate

How to do a quality check of AAC blocks Masonry

Who does not desire to live in a safer and stronger-built home? Houses built with AAC Blocks have many characteristics that are not found in houses made with red clay bricks.

Autoclaved Aerated Concrete is an eco-friendly and certified green building material that is lightweight, high-insulating, durable building blocks, and three times lighter when compared to red bricks.

AAC blocks use 65 to 70% fly ash, a waste generated from a thermal power plant. It does not require clay, so no damage to agricultural land and soil. 

AAC blocks are three times lighter than clay bricks and four times lighter than concrete blocks, so more blocks are transported in the exact vehicle, saving fuel for transportation than clay bricks / Concrete blocks. 

Green building certifying organizations like LEED, IGBC, BREEAM, DGNB, CASBEE Certify AAC blocks as a green building material.

AAC lightweight blocks are porous, non-toxic, renewable, and recyclable also.

The information given in this article is based on relevant IS codes and sound construction practices. Kindly make sure that your site supervisor or contractor follows the instructions to get the full benefits of AAC building material. 

We have suggested a few measures through which you can do a quality inspection and see if the block used in the construction is suitable or not.  

Stacking:

Stack AAC Blocks on a flat and dry surface; avoid stocking AAC Blocks on uneven and wet surfaces. Stacking should done on even and leveled ground surfaces.

Mortar for Masonry:

Thin Bed mortar is a new technology that offers an extremely thin-joint (~3 mm) alternative to the conventional mortar. Thin Bed mortar is factory-mixed mortar manufactured as per predesigned chemical formula; it constitutes cement, graded sand, and blended with polymers. Even at ~3 mm thickness, it imparts high strength and water retention properties. 

In Thin Bed mortar, the laying of AAC Blocks requires only 3 mm to 5 mm thickness. 

Mortar Thickness:

Conventional Mortar: Before laying AAC Blocks, apply 8 mm to 10 mm thick lean cement mortar uniformly over the block, and it requires curing the joints after laying. Thin Bed mortar: apply only ~3 mm thick layer uniformly over the block and no curing required.

Wetting Of Block: 

Each block needs to be made wet with a sponge on all sides of the mortar contact surface, and place them one by one, pressing it firmly to have a proper bond without any level difference, and fill joints between the blocks with the same mortar. (Do ‘not’ soak the blocks).

Coping Beam (Bond Beam):

For AAC blocks, it is recommended to minimize the effect of shrinkage, tensile, & diagonal cracking, and to enhance stability, it is recommended to provide bed joints reinforcement or nominal bond beams. 

Bond Beam should be provided after every 1200mm (5-6 layers). 2 TMT bars of 8 mm dia should use along with a 6 mm dia stirrup. Ensure that the reinforcement rods are insert into surrounding columns for load transmission. The height of the beam should be more than 80 mm and filled with M15 grade concrete.

Masonry joint reinforcement expanded wire mesh or other suitable substitutes should be provided on every alternate layer. The out to out spacing of the longitudinal wire shall be 50 mm less than the width of the wall.

To achieve the desired tensile strength overlap should be around 75 mm.

Expanded wire mesh uses while using thin-bed mortar.

Curing of Masonry Wall: 

When the AAC block wall needs to reinforce then, that considered a structural masonry wall. Vertical reinforcement can install within the block cells and filled with mortar. Horizontal reinforcement might be needed as well, using prefabricated welded wires placed along the horizontal joints of between courses. The horizontal support will also prevent or control shrinkage cracking. 

Curing requires only cement mortar joints and not needed for ready-made mortar jointing.

Cutting of Block: 

AAC Blocks do not require full wall curing (unlike bricks). Avoid water bucket flooding on AAC Blocks.

Curing requires only at the traditional mortar joints (for a max of 7 days, twice a day) so that there is adequate water availability for mortar curing. Joint curing done using a nozzle sprayer.

Lintel support:

Apply Lintel where required, install lintels with a minimum 8″ bearing (overlap) where required. Where stresses under lintel bearing exceed permissible values (e.g., under heavy concentrated loads), should incorporate concrete spreaders or pad stones. And can avoid cold bridging at lintel positions by using AAC with appropriate types of lintels. This allows the insulating properties of AAC blocks to be continuous across the wall face & facilitate subsequent door & window fasteners.  

Plaster: 

AAC walls should plastered on both sides of the wall, i.e., internal and external sides of the wall.

Plastering thickness should be 10 mm for internal walls. Avoid plastering more than 10-12 mm thick, as it can result in cracks.

External plastering has to carried out in two coats; applying SBR coating with sand on the block surface will enhance the bonding and minimize the thickness of plastering. Plastering thickness can be 12-15 mm for external walls, based on external forces acting on the wall. 

Electric & Sanitary Chases:

Chases to be grooved before plastering the wall using an electrical cutter and chiseled gently without hammering to avoid damages to walls. 

When laying grooves, must take adequate care to ensure the structural integrity of the AAC blocks is maintained. If conventional cement mortar is used for joints, please start electrical after a minimum of 10 days of curing. 

Aadil

Aadil Bandi is a professional blogger and digital marketing consultant. He has a decade of experience writing digital marketing, business, real estate, and home improvement content. He is based in Ahmedabad, but you can find him on Twitter and LinkedIn.

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