15 Expert Tips for Seamless AAC Blocks Installation

Walling Solutions
15 Expert Tips for Seamless AAC Blocks Installation
Magicrete

05 Feb 2024
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1. Storing

During storage, it is crucial to prevent continuous water contact and refrain from using wet/water submerged blocks for masonry.
If, for any reason, the blocks have become wet, it is essential to ensure they are thoroughly dried before usage.
To prevent corner chipping, it is advisable to avoid stacking blocks directly on top of each other; instead, alternate layers every 3-4 layers during stacking.
The stacking height should not exceed 1.2/1.5 meters to maintain stability and safety.

2. Pre work preparation

Opt for a minimum of 100 mm thickness for internal wall blocks and 150-200 mm for external walls.
Adjust designs if thinner blocks are needed.
Plan layout, count blocks, and gauge sizes beforehand.
Avoid creating block holes for scaffolding; use concrete for support.
Moistening blocks with a wet brush 24 hours before masonry is advisable.

3. Mortar preparation

AAC masonry can employ either traditional mortar or specially formulated thin bed mortar.
Traditional Mortar - Maintain a 1:6 Cement: Sand ratio; avoid 1:4 high cement mortar. Consider PPC usage. Typically, use 10mm to 15mm thickness with traditional mortar to allow for movement without overly rigid joints.
The goal is to achieve joints that offer flexibility, not excessive hardness.
Thin bed Mortar - Opt for Thin Bed Mortar or Magicrete Block joining Mortar.
containing the right blend of sand, cement, and additives applied at 3mm thickness.

4. Laying of masonry

Avoid block soaking; moisten with a wet brush to deter water absorption.
Begin with a thick layer of traditional cement-sand mortar for levelling the bottom.
Start by laying corner blocks first.
Verify uniform block height using a level-o-meter.
Maintain consistent masonry pattern with at least 1/3rd or 200mm overlap.

5. Curing of masonry

AAC Blocks need no complete wall curing as with bricks. Avoid flooding AAC Blocks with water buckets.
Curing is solely necessary at traditional mortar joints (up to 7 days, twice daily) to ensure ample water for mortar curing; employ a nozzle sprayer for joint curing.

6. Nominal bond beam (Coping)

Option 1 - For minimizing shrinkage and enhancing stability, consider using bend joint reinforcement or nominal bond beams.
- Bond beams, after every 1200 mm (5-6 layers), require 2 TMT bars of 8 mm diameter and a 6 mm diameter stirrup.
- Ensure rods extend at least 60 mm around columns for load transmission.
- Maintain a beam height exceeding 80 mm, and fill with recommended M15 grade concrete.

Option 2 - Incorporate masonry joint reinforcement like expanded wire mesh or Magicrete Power Mesh, an appropriate alternative on every other layer.
- Longitudinal wire spacing should be 50 mm less than the wall width for optimal results.
- To achieve the desired tensile strength, aim for a 75 mm overlap.

7. Top layer/ Side layer

Seal top and side joints using polyurethane foam or a lean (1:8 or 1:10) cement-sand mortar to prevent the transfer of ceiling deflection loads onto walls.
Leave 10-20 mm gaps at the wall's top; after 2 weeks, fill them with polyurethane foam to prevent cracks from structural deformation and allow wall flexibility during drying shrinkage.

8. Joints of dissimilar materials

Before plastering, isolate contact surfaces from dissimilar materials using lean mortar or PU foam and synthetic fibre mesh or chicken mesh.
Apply chicken mesh or fibre mesh at door and window corners, beam and column interfaces, and PB joints.

9. Chiselling

When installing electrical conduits or pipes, use an electrical router or chasing tool to create a chase. Employ a power drill or router for electrical box installation.
Avoid chasing adjacent to each other in thinner blocks; limit chase depth to 1/3 of wall thickness.

10. Fasteners

When installing electrical conduits or pipes, use an electrical router or chasing tool to create a chase. Employ a power drill or router for electrical box installation.
Avoid chasing adjacent to each other in thinner blocks; limit chase depth to 1/3 of wall thickness.

11. Control joints or Mullion

For walls longer than 6.0 meters, include a 10 mm wide movement joint beginning 3 meters from a corner. Fill this joint with a resilient material and seal both ends to block rainwater. Depending on block thickness, incorporate dummy/stub columns.

12. Internal Plastering

To prevent drying shrinkage cracks, plaster only on fully dried walls.
Avoid plastering just before peak tropical summers to prevent excessive drying.
Gypsum Plaster suits internal walls due to its non-shrinking property. Alternatively, use a 1:6 cement-sand mortar for a 6 to 12mm thick first coat on interior walls.
Apply a 2 to 3mm thick second coat of lime fresh or putty.
Strengthen by applying a 16-gauge wire mesh over the entire wall surface before plastering.

13. External Plastering

Avoid wet or monsoon walls for plastering. Wait until they're dry.
Use a 12mm 1:6 cement-sand mortar for the first coat, 5-10mm for the second.
Enhance bonding with a thin Magicrete Unibond layer before plastering.
Blend Magicrete Unimix or any waterproofing compound into the plaster.

14. Beam defection and movement

A beam above a wall may deflect due to load or temperature-induced movement. According to IS 456:2000, beam deflection can occur from Point load and bending at a ratio of L/250, not exceeding 20mm.
Ensure a 10-15mm gap and fill it with a flexible material like backer rod/lean mortar (1:8) and secure it with 10mm aggregate. This prevents ceiling/beam deflection from transferring loads to the wall.

15. Shear and tensile loading

Cracking in walls can appear near door and window frame corners, specifically at lintel and sill levels due to shear and tensile forces.
To mitigate this, it's recommended to incorporate nominal reinforced concrete bond beams at both sill and lintel levels.
These bond beams serve to safeguard the wall against shear stresses, thereby preventing cracks due to shearing forces.

Conclusion

Meticulous installation transforms AAC block projects into immensely rewarding ventures. Incorporate these expert tips to guarantee a smooth installation process, saving both time and resources, and culminating in a resilient, energy-efficient structure. Ready to elevate your construction game? Implement these insights for a project that stands the test of time.