CLC (Cellular Lightweight Concrete) Calculator: Complete Guide
What is Cellular Lightweight Concrete (CLC)?
Cellular Lightweight Concrete (CLC), also known as foam concrete or foamed concrete, is a cement-based material in which a large portion of the volume consists of air voids intentionally introduced by adding a pre-formed foam. The result is a lightweight, thermally efficient material with densities ranging from 400 to 1800 kg/m³ — compared to 2400 kg/m³ for normal concrete.
CLC is widely used for roof insulation, partition walls, floor screeds, and precast panels. Its low weight reduces structural loads, and its cellular structure provides excellent thermal and acoustic insulation. Unlike autoclaved aerated concrete (AAC), CLC is cured at ambient conditions and can be produced on-site with relatively simple equipment.
CLC Mix Design Formulas
The CLC mix design is based on absolute volume method:
- C = Cement content (kg/m³), specific gravity 3150 kg/m³
- SCM = Supplementary material (fly ash, GGBS), with appropriate SG
- Sand = Fine aggregate, SG 2650 kg/m³ (0 for ultra-light mixes)
- Water = Mix water (L/m³), density 1000 kg/m³
The remaining volume after solid components is filled with pre-formed foam. The wet density is approximately equal to the total solid material weight per m³, since foam adds negligible mass.
Foaming Agents for CLC
The foaming agent is diluted in water and passed through a foam generator to produce stable foam:
| Agent Type | Dilution | Expansion | Stability |
|---|---|---|---|
| Protein-based (BASF) | 1:35 | 1:28 | Very High |
| Synthetic (SFRA) | 1:25 | 1:22 | High |
| Plant-based / Natural | 1:20 | 1:18 | Medium |
| Hydrolyzed Keratin | 1:40 | 1:32 | Very High |
| Saponin (Soap Root) | 1:15 | 1:15 | Low–Medium |
Protein-based agents (from hydrolyzed animal protein) produce the most stable foam and are preferred for structural CLC. Agent dosage: typically 1–4 litres per m³ of CLC depending on target density.
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CLC Applications by Density
- 400–600 kg/m³: Void fill, sub-floor insulation, annular space grouting
- 600–800 kg/m³: Roof insulation slabs, non-structural partitions
- 800–1000 kg/m³: Internal partition walls, floor screeds, precast blocks
- 1000–1200 kg/m³: External walls, semi load-bearing partitions, precast panels
- 1200–1600 kg/m³: Structural panels with reinforcement, load-bearing walls
Density vs. Strength Relationships
The compressive strength and thermal conductivity of CLC can be estimated from dry density using empirical formulas based on published research (Jones & McCarthy, 2005):
λ ≈ 0.038 × (D/100)^0.5 (W/m·K)
where D = oven-dry density in kg/m³. These are approximations — actual values depend on cement type, curing age, and mix design. The density-strength calculator in this tool uses these formulas.
FAQs
What is the difference between CLC and AAC?
CLC (Cellular Lightweight Concrete) uses pre-formed foam mixed into a cement slurry and cured at ambient conditions. AAC (Autoclaved Aerated Concrete) uses a chemical reaction (aluminum powder + cement) and requires high-pressure steam curing in an autoclave. CLC can be produced on-site; AAC requires factory manufacturing.
What density should I target for CLC blocks?
Standard CLC blocks for partition walls are typically 800 kg/m³. External walls may use 1000–1200 kg/m³ for better structural performance. Roof insulation fill is often 400–600 kg/m³. Use our Density vs Strength calculator to find the right balance for your application.
How much foaming agent do I need per m³ of CLC?
Agent usage depends on the target foam volume and the agent type. For 800 kg/m³ CLC with protein agent (1:35 dilution, 1:28 expansion): approximately 1–2 litres of agent per m³. Use the Foam & Agent Calculator tab for precise values based on your inputs.
Can fly ash replace cement in CLC?
Yes. Fly ash (Class F) can replace 30–50% of cement in CLC mixes. This reduces cost and CO₂ emissions. GGBS (Ground Granulated Blast Furnace Slag) is another common SCM. Both improve long-term strength and workability. Select the SCM type and quantity in the Mix Design calculator.