Quality & Testing
Quality and testing of lightweight concrete block
Quality that is not measured is only a claim. For Redblok we record fresh and dry density, compressive strength, water absorption, shrinkage and foam stability for every batch. Cellular lightweight concrete lies outside the scope of TS EN 206, so its performance is defined by the project specification and laboratory testing. On request we add these records to your project file.
Standards and certificates
- TS EN 206Concrete standard; cellular lightweight concrete is outside its scopeReference; performance defined by testing
- TS 13515Complementary standard for the application of TS EN 206Reference; performance defined by testing
- TS EN 1992Design of concrete structures (Eurocode 2)Applied as the basis of design calculations
- CEConstruction Products Regulation conformity markingTargeted at production start-up
Compressive strength test · illustrative image
Control
What do we measure, and how often?
The table shows the typical control plan in Redblok production.
| Fresh density | Every mix / before placing |
|---|---|
| Dry density | Every batch / specimens after curing |
| Compressive strength | Every batch / cube specimens in the laboratory |
| Water absorption | Per mix design and batch |
| Shrinkage and dimensional stability | Per mix design / laboratory |
| Foam stability | Every shift / foam density measurement |
| Block size and squareness check | Every batch / after cutting |
Mix design
Density class, strength and insulation targets.
Lightweight concrete is not a single product. You choose a density first; strength and thermal conductivity follow from that choice. The table shows the band we target in block production.
| Class | Dry density | Compressive strength (28 d) | Thermal conductivity | Water absorption (by volume) | Typical use |
|---|---|---|---|---|---|
| KB300 | 300 ± 50 kg/m³ | 0.5 – 0.9 MPa | 0.08 – 0.10 W/mK | 8 – 12 % | Insulation first; the lightest block class |
| KB400 | 400 ± 50 kg/m³ | 0.9 – 1.6 MPa | 0.10 – 0.12 W/mK | 8 – 12 % | Insulation first; light partition block |
| KB500 | 500 ± 50 kg/m³ | 1.5 – 2.5 MPa | 0.12 – 0.14 W/mK | 10 – 14 % | Partition wall block |
| KB600 | 600 ± 50 kg/m³ | 2.2 – 3.5 MPa | 0.14 – 0.17 W/mK | 10 – 14 % | Partition and infill wall block |
| KB700 | 700 ± 50 kg/m³ | 3.0 – 4.5 MPa | 0.17 – 0.20 W/mK | 12 – 16 % | Infill wall block |
| KB800 | 800 ± 50 kg/m³ | 4.0 – 6.0 MPa | 0.20 – 0.24 W/mK | 12 – 16 % | Infill wall block where higher strength is needed |
| KB1000 | 1,000 ± 50 kg/m³ | 6.0 – 9.0 MPa | 0.26 – 0.32 W/mK | 14 – 18 % | Non-structural high-density block |
These are design targets, not commitments. Results shift with the mix, the foaming agent and curing conditions. For each class we make a trial mix, take samples and verify performance by laboratory testing. Project-specific values are issued with that test report.
Approach
What did we develop the mix for?
The known weak point of non-autoclaved concrete is lower strength and higher drying shrinkage than an autoclaved product of the same density. We developed the mix around that point: each density class has its own mix, and admixtures and ratios are proprietary. We show the result with values measured on every batch, not with claims. In a lightweight wall the real cost is often not the material; it is broken blocks, waste and rebuilding.
- 01
Binder: cement and a mineral addition
The main binder is Portland cement. We replace part of it with a mineral addition, which helps keep the air pores stable and lowers shrinkage. The type and ratio of the addition are proprietary.
- 02
Fine material: by density
At 500 kg/m³ and below the mix has no aggregate; the binder paste and foam form the body. In higher classes we add fine material. Strength rises, and thermal conductivity rises a little too.
- 03
Water: a low ratio
We keep water low and get workability from a plasticising admixture. Less water improves both strength and foam stability. The most common mistake with lightweight concrete is adding water to make the mix easier to handle.
- 04
Foam: fine, stable pores
We make the foam in the generator at a dose calculated from the target fresh density. The aim is fine, closed pores. The choice of agent and the foam density are proprietary.
- 05
Fibre: against shrinkage cracking
We add micro-fibres to the mix. They limit the plastic shrinkage cracks caused by fast surface drying in the mould and during curing. In the hot season this step is decisive.
- 06
Density control: every mix
We measure fresh density in a container on every mix and compare it with the target band. A small drift in the foam changes fresh density. If you want no surprises in the hardened block, this is the checkpoint.
- 07
Curing: the first seven days
For the first 24 hours after casting we cover the blocks against moisture loss, then cure them under control for seven days. Early drying is the most common cause of strength loss and shrinkage cracking in lightweight concrete.
Tell us about your project and let our engineers assess it.
Start with a wall quantity, a block size, a project drawing or simply a requirement brief. We respond within 24 hours.