Jointing and Curing Techniques for AAC Block Walls: A Complete Guide

Introduction to AAC Blocks

AAC (Autoclaved Aerated Concrete) blocks are lightweight, precast building materials known for their thermal insulation, fire resistance, and structural efficiency. While Featherlite Buildcon manufactures FlyAsh Blocks—a distinct product—AAC blocks share some similarities in application techniques. Proper jointing and curing are critical to ensuring durability and performance in masonry construction.

Benefits of AAC Block Construction

AAC blocks offer several advantages in modern construction:

• Lightweight, reducing dead load on structures
• High thermal insulation, lowering energy costs
• Precision in dimensions for uniform joints
• Fire-resistant properties as per IS 2185 (Part 3)

Essential Jointing Techniques for AAC Blocks

Choosing the Right Mortar

Traditional cement-sand mortar is less suitable for AAC blocks due to their low absorption. Instead, use:

• Thin-bed adhesives (recommended for uniform joints)
• Polymer-modified mortars for better bonding

Note: Mortar selection should comply with IS 2250 for masonry work.

Correct Joint Thickness and Application

AAC blocks require thin joints (2–4 mm) to minimise thermal bridging and stress. Key steps:

1. Clean the block surface to remove dust
2. Apply adhesive evenly using a notched trowel
3. Press blocks firmly into place without excessive adjustment

Dealing with Movement Joints

To accommodate thermal expansion and shrinkage:

• Install vertical movement joints every 6–8 metres
• Use flexible sealants compatible with AAC material

Proper Curing Methods for AAC Block Walls

Initial Curing Process

The first 7 days are critical:

• Keep walls moist by light water spraying twice daily
• Protect from direct sunlight with damp hessian cloth
• Avoid load-bearing for at least 24 hours after laying

Long-Term Curing Considerations

For optimal strength development:

• Maintain ambient humidity above 50% for 28 days
• Delay plaster application for 2–3 weeks to allow drying shrinkage

Common Errors in Jointing and Curing

Avoiding Cracks in AAC Block Walls

Prevent cracking by:

• Ensuring proper curing as per NBC guidelines
• Using reinforcement at stress concentration points
• Avoiding rapid drying through wind exposure

Ensuring Proper Adhesion

Poor bonding leads to delamination. Solutions include:

• Surface preparation with wire brushing
• Using primers for adhesive mortars when needed
• Avoiding mortar skinning (applying on partially set mortar)

Best Practices for Optimum Results

Key recommendations for AAC block masonry:

• Store blocks under cover to prevent moisture absorption
• Plan electrical conduits to minimise chasing
• Use only compatible plasters (e.g., polymer-modified mixes)

FAQs on AAC Block Jointing and Curing

Q: Can AAC blocks be laid with traditional mortar?
A: While possible, thick cement-sand joints compromise thermal performance and may lead to cracking. Thin-bed adhesives are preferred.

Q: How soon can AAC walls be plastered?
A: Wait 14–21 days to allow initial shrinkage before plaster application.

Q: Do AAC blocks need waterproofing?
A: In exposed areas, use breathable waterproof coatings to prevent moisture ingress while allowing vapour diffusion.