Block Masonry [ACC/ CLC/ Concrete]

1. Introduction
2. Manufacturing and production
2.1 AAC (autoclaved aerated concrete)
2.2 CLC (cellular lightweight concrete)
2.3 Concrete blocks (solid and hollow)
3. Standards and codes
4. Types and properties
5. Design and fixings
6. Mortar compatibility
7. Common failures and troubleshooting
8. QA and QC items
9. BOQ lines
10. Method statement — AAC block laying
Disclaimer

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Purpose: consultant-ready guide to block masonry (AAC, CLC, concrete). Use the TOC to jump to manufacturing, standards, types and properties, design and fixings, mortar compatibility, failures, QA, BOQ, and method statement.

1. Introduction

AAC and CLC blocks are lightweight engineered masonry units that provide thermal insulation and fast construction. Concrete blocks (solid and hollow) are durable and used in load-bearing and partition walls.

2. Manufacturing and production

2.1 AAC (autoclaved aerated concrete)

Raw materials: cement, lime, fly ash, gypsum, aluminum powder (gas agent).
Mix and pre-curing: slurry generates hydrogen microbubbles.
Cutting: after initial set, cut by wire on casting bed.
Autoclaving: ~180°C and ~12 bar steam curing for strength and volume stability.
QC: density (kg/m³), moisture content, dimensional accuracy.

2.2 CLC (cellular lightweight concrete)

Cement + fly ash + preformed foam (stable bubbles).
Ambient curing; density set by foam volume. Lower strength than AAC but cost-effective.

2.3 Concrete blocks (solid and hollow)

Crushed aggregates + cement mix in vibration molds.
Cure wet or in chamber; ensure adequate compaction to avoid voids.

3. Standards and codes

IS 2185 (Part 3) — AAC block specification.
IS 6041 — CLC block guidelines.
IS 2572 — Hollow concrete blocks laying.
Manufacturer TDS for adhesives and thin-bed systems.

4. Types and properties

Type	Density (kg/m³)	Compressive strength (MPa)	Water absorption	Thermal conductivity	Remarks
AAC block	550–650	3–4	10–12%	≈ 0.16 W/m·K	Low dead load, energy-efficient
CLC block	700–900	2.5–4	12–18%	≈ 0.18 W/m·K	Good sound insulation
Concrete block	1900–2000	5–15	6–10%	≈ 1.2 W/m·K	Durable and impact resistant

Dimensional tolerances: ± 2–3 mm on faces for AAC; thin-bed adhesive required.

5. Design and fixings

Thin-bed adhesive: 3–4 mm adhesive beds for AAC (faster, reduced thermal bridging).
Anchors and fixings: Nylon/metal anchors with verified pull-out performance. For heavy loads, use chemical anchors or resin-grouted sleeves in filled cores.
Joints: 3–4 mm thin-bed for adhesives; if cement mortar used, 10 mm nominal.
Reinforcement: Provide vertical bars in grouted cavities for seismic/structural needs. Integrate lintel beams per structural drawings.

6. Mortar compatibility

AAC/CLC: Thin joint adhesive (3–4 mm) instead of cement mortar.
Concrete block: Cement–sand mortar 1:6.

7. Common failures and troubleshooting

Symptom	Cause	Diagnostics	Solution
Corner breakage during handling	Poor handling; high block moisture	Edge spall inspection	Improve storage/handling; use pallets
Poor adhesion to thin-bed	Dusty or uneven surfaces	Shear test	Clean, prime if required, correct trowelling
High water absorption and damp	Blocks stored exposed to rain	Moisture meter	Dry stock before use; pre-soak if TDS recommends
Thermal cracking in external walls	Insufficient movement joints	Crack mapping	Add movement joints; consider insulation composite cladding

8. QA and QC items

Accept material with MTC and batch density report.
Dimensional checks each pallet (sample three blocks).
Adhesive bed thickness check 3–4 mm.
Pull-out test sampling: one per 100 anchors.
Mock-up panels for external render and finish.

9. BOQ lines

AAC block masonry 200 mm with thin-bed adhesive (supply and fix) — m²
AAC external thin coat render 15 mm — m²
Filling of hollow cores with non-shrink grout and reinforcement — m
Supply and fix block lintel (grout + reinforcement) — m

10. Method statement — AAC block laying

Scope and references: IS 2185 (Part 3) and manufacturer TDS.
Materials and storage: Accept per MTC; store dry under cover on pallets.
Work sequence: Set out lines; apply 3–4 mm adhesive bed with notched trowel; press block with light taps; remove excess; install ties and vertical reinforcement; provide lintels/bond beams at openings.
Curing and protection: Cure per TDS; protect from rain and full sun 24–48 hours; prime and scratch coat before external finishes as required.
QA checks and tests: Bed thickness, adhesion pull tests, dimensional and plumb checks.

Disclaimer

Conix is an industry initiative & a neutral resource, compiled from industry references and best practices. It is not brand-specific. Always cross-check with project requirements and local codes before finalizing specifications.