Cellular Concrete: Blocks, Partitions and Foamed Concrete — The Guide

When a Moroccan mason says “cellulaire”, he almost always means cellular blocks — those pale, light blocks that cut with a hand saw and raise partitions at disconcerting speed. But the term also covers foamed concrete poured in place, used for fills and screeds-to-falls. Two products, two trades, one principle: millions of air voids that lighten, insulate and ease installation. This guide separates the two, gives the selection criteria and the laying rules that prevent disappointment.

Cellular blocks: the industrial product

Autoclaved aerated concrete (AAC) is born from a chemical reaction: sand, lime, cement and an aluminium powder that releases hydrogen — the mix rises like a cake, then hardens in an autoclave (pressurised steam). The result: a block with a fine, regular alveolar structure, between 400 and 700 kg/m3 against over 1,800 for a classic hollow block, that cuts with a saw, planes like wood and is laid on thin-bed adhesive — a 2-3 mm joint instead of the 10-15 mm of traditional mortar. Its qualities make it the king of partitions: light (one-hand lifting, less fatigue and handling), respectable thermal insulation, clean cutting for services and sockets, smooth finish that reduces render thickness.

Foamed concrete: alveolar on site

Foamed concrete is made on site or at the plant: a surfactant foam is injected into a cement mortar (sometimes with fine sand or filler), and the poured mix keeps its bubbles while hardening. Programmable densities from 400 to 1,600 kg/m3 depending on foam dose and cement content. Its territories: infill of trenches and voids, screeds-to-falls on flat roofs, lightened slabs, level make-ups, pipe bedding. It pumps, pours with a float, rules to level — a filling and shaping product, never structural.

The golden rule: cellular fills, it does not carry

This is the line to engrave: cellular — block or foam — carries its own weight and nothing else. Any concentrated load (lintel, beam bearing, wall-hung water heater, safe) demands a hard point in classic reinforced concrete: cast lintel, steel plate, ring beam. Cellular-block construction does this systematically: horizontal and vertical reinforced ring beams, lintels above openings, bonding course at the top. Forget these hard points and one day you discover stair-step cracks above openings — the sign of a locally crushed block where it should never have carried.

Laying blocks: the method that makes a wall straight

Laying starts with first-course setting out: measure, cut the first courses to dimension (the block cuts — use that — no jammed joints). The first course goes on normal cement mortar (CPJ 45, classic masonry dosage) to pick up the level of the support — the only course using a thick mortar. All following ones are glued: cellular thin-bed adhesive prepared per the datasheet, applied with a notched trowel, block set and tapped with a rubber mallet, regular thin joints. Every course is checked with a spirit level and string line; a badly laid cellular wall cannot be fixed by render. Electrical and plumbing chasings are routed with a groove cutter — the material works like wood.

Where cement comes in

The cellular block is bought ready-made — we do not manufacture it, and DAM sells cement, not blocks. But cement is everywhere around it: bedding mortar of the first course, reinforced concrete of ring beams and lintels, finishing renders (renders on cellular demand adapted products — a too-rigid cementitious render cracks on a substrate that “moves” differently), fixings and make-ups. For these accompanying concretes and mortars, CPJ 45 covers most everyday needs; CPJ 55 serves demanding ring beams and hard points. And if your project targets a lightened roof with poured foam falls, the cement of that foam must be consistent and documented — the formula is batch-sensitive.

The recurring mistakes

• Making a cellular block carry a concentrated load without lintel or reinforced hard point.
• Laying on thick adhesive like a hollow block: thin-bed is the very principle of the product.
• A mediocre first-course level: the whole wall inherits the error.
• Unsuitable render on alveolar substrate: facade cracking in the first season.
• Foam poured to carry: it is a fill, not a structure — same rule as blocks.
• Storing blocks unprotected: delivered dry, they drink the water of fresh mortars and renders around them.

What DAM supplies — and does not

We produce grey CPJ 45 and CPJ 55, compliant with NM 10.1.004, delivered in Dakhla and the region, with a certificate per batch. Cellular blocks, thin-bed adhesives and foams come from specialised manufacturers and distributors — our role is the cement of the concretes and mortars surrounding the cellular: ring beams, lintels, fixings, preparatory renders, and the poured foam if your site plans one. Tell us the volumes and the schedule, and we will frame delivery with your masonry phases.

In summary

Cellular = voids: industrial AAC blocks for partitions (light, straight, insulating, thin-bed), poured foam for filling and falls. The non-negotiable boundary: it fills, it does not carry — lintels and ring beams stay reinforced concrete. Around it, classic cement does the work: CPJ 45 for everyday, CPJ 55 for hard points, renders suited to the substrate, and a cared-for first course that decides the straightness of the whole wall.