Pouring a Concrete Slab: Mix Ratio, Thickness and Method

Direct answer: a slab on grade is poured at 300 kg of cement per m³ for standard use — 350 kg/m³ for a reinforced floor slab — at 10-15 cm thickness depending on use, with welded mesh on spacers, polythene sheeting, 7-day curing and joints cut every 4-6 m. For 20 m² of 12 cm slab: 2.4 m³ of concrete, about 15 fifty-kg bags — or one ready-mix truck.

Mix ratio and thickness by use

The ratio-thickness pair is chosen by the slab's destination. A pedestrian terrace does not work like a driveway, and an industrial floor belongs to engineered design. As standard rules:

The method in 5 steps

1. Prepare the base. Excavate to level, 20-30 cm of hardcore compacted in layers, polythene sheet covered and turned up at the edges — without it, rising damp crosses the slab for life. 2. Place the reinforcement right. Welded mesh on spacers, in the bottom third of the thickness; laid flat on the sheeting, it does nothing. 3. Pour. Concrete at 300-350 kg/m³, placed without segregation, vibrated or tamped, floated surface; in hot weather, pour in the morning and protect immediately.

4. Cure for 7 days. Watering, curing film or wet geotextile: the most cost-effective site measure against cracks, dust and capped strength. 5. Cut the joints. A 4-6 m grid, one third of the thickness deep, within 24-48h of pouring: a designed joint always beats an endured crack.

The mistakes that ruin a slab

• Mesh laid flat at the bottom: the steel does not work — the number-one error behind cracked slabs;
• Polythene sheet forgotten: capillary rise, stains, tiles that lift;
• Water added on site for workability: every excess litre costs 2-3 MPa — a plasticiser does the same job without breaking anything;
• No curing: the surface dries before it hardens, dusts and cracks;
• Joints forgotten or too far apart: shrinkage will draw them for you, wherever it wants;
• Pouring at 35 °C in full sun: fast loss of workability, plastic shrinkage, crocodile-skin cracking.

On site or ready-mix?

Below 2-3 m³, site-mixed concrete — 6-7 bags per m³ depending on ratio, clean sand and gravel, measured water — remains viable with a mixer and method. Beyond that, or for any slab meant to last: ready-mix concrete delivered by truck guarantees constant ratio, continuous placement and certified strength. DAM serves both worlds: CPJ 45 cement in bags or big bag for mixing sites, and ready-mix concrete for pouring days.

Price your slab in three minutes with our calculator — volumes, bags, ratio — then request a quote: within 24h in Dakhla, the slab only waits for your calendar.