C2–C6 / Foamed Concrete
Foamed concrete (sometimes called foam-crete or lightweight cellular concrete) covers mix strength grades in the range of C2 to C6 (approx. 2–6 N/mm² compressive strength). This material is characterised by a high volume of entrained air bubbles, giving low density and high workability. It is not used for primary structural load-bearing concrete; rather, it is ideal for fill, insulation, reinstatement, void filling or trench back-fill where heavy loads are not the target.
Technical details
- The low strength (2-6 N/mm²) means the material cures relatively quickly to its design strength
- Being flowable, it minimises manual compaction and can fill awkward spaces or voids with minimal disturbance
- Because it is lightweight, it reduces the imposed load on surrounding structure or ground – useful for voids beneath slabs, abandoned basements, or channels
- Typical densities might be in the 300-1600 kg/m³ range depending on air content, so you get thermal / insulation benefits in some cases
- Workable life: the mix typically remains workable for up to around 3 hours, and can often be surfaced (or overlaid) within 24 hours depending on thickness and mix design.
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Typical applications & key benefits
Typical applications
- Trench reinstatement after utility work
- Filling abandoned concrete structures or basement voids
- Structural stabilisation beneath slabs or foundations
- Insulating fill where lighter weight is beneficial
- Where access is tight and compaction plant would be heavy/hard to mobilise
Key benefits
- Reduced labour and plant costs (because compaction is not required)
- Faster programme – quick placement, often no long wait for subsequent works
- Flowable – can fill odd shapes or voids easily
- Lightweight – reduces load on existing foundations or ground
- Versatile – mix can be tailored on site for the required strength range
Ordering & delivery advice
When ordering, provide: trench / void dimensions (length/width/depth), access constraints (pumping required?), required finish or overlay timing, and any special curing needs (e.g., if you’ll traffic the surface early).
Also consider: ground conditions (are there aggressive salts/chemicals?), final design loading, and any requirement for reinforcement (though typically foamed fill is unreinforced).
