Post-Tensioned Ground Slabs
Crack-free industrial floors with fewer joints and an extended service life.
What is a post-tensioned ground slab?
A post-tensioned ground slab (or post-tensioned slab-on-grade) is a concrete slab cast directly on the ground, reinforced by prestressing cables stressed after curing. Unlike a traditional reinforced concrete slab-on-grade that works in compression under its own weight and in tension under applied loads, a post-tensioned slab is held in permanent compression in both directions. This compression prevents the formation of shrinkage and flexural cracks that systematically affect conventional slabs.
The system uses greased and sheathed monostrands (individual cables protected by an HDPE sheath filled with anti-corrosion grease) laid on the prepared subgrade in a grid pattern calculated according to the live loads and the bearing capacity of the soil. After the concrete is cast and has reached a minimum strength of 25 MPa, stressing is carried out from the slab perimeter.
How does post-tensioning improve industrial floors?
The main enemy of industrial floors is cracking. A conventional reinforced concrete slab-on-grade inevitably cracks due to concrete shrinkage and thermal stresses. These cracks require closely spaced expansion joints (every 5-6 metres), create weak points under rolling loads, and degrade floor flatness over time.
Post-tensioning solves these problems by maintaining the concrete under a minimum compression of 0.7 to 1.5 MPa in both directions. This compression neutralizes the tensile stresses caused by shrinkage, allowing expansion joints to be spaced at 40-60 metres instead of 5-6 metres. The reduction in the number of joints — which are the most vulnerable points in any floor slab — significantly extends the life of the structure and reduces maintenance costs.
Advantages over conventional slabs-on-grade
Cracking is reduced by approximately 80% compared with a conventional reinforced concrete slab. This near-absence of cracks preserves floor flatness — a critical criterion for warehouses using reach trucks or automated storage systems requiring strict FL/FM tolerances.
Slab thickness can be reduced by 15 to 20% compared with reinforced concrete, lowering concrete consumption and earthworks costs. On poor-quality soils (expansive clay, recent fill), a post-tensioned slab better tolerates differential settlement thanks to its stiffness and ability to redistribute loads.
Maintenance costs are significantly reduced over the life of the structure. Expansion joints — which require regular maintenance (every 2-3 years under heavy use) — are 8 to 10 times fewer. The total cost over 20 years is 25 to 35% lower than that of a conventional slab requiring frequent repairs.
Typical applications
Post-tensioned ground slabs are the benchmark for logistics warehouses (areas of 5,000 to 50,000 m²), distribution platforms under heavy rolling loads, factories requiring perfect flatness for production lines, and cold stores where thermal stresses aggravate cracking. BEPCO has delivered over 200,000 m² of post-tensioned ground slabs in West Africa.
Key Benefits
80% less cracking
Permanent compression neutralizes concrete shrinkage and prevents crack formation.
Widely spaced joints (40-60 m)
Instead of 5-6 m in RC, drastically reducing weak points and maintenance.
Superior flatness
FL/FM tolerances maintained over time, even under heavy rolling loads.
Extended service life
25-35% saving on maintenance costs over 20 years compared with conventional slabs.
Frequently Asked Questions
Why post-tension a ground slab?
Post-tensioning keeps the concrete in permanent compression, preventing the shrinkage cracking that affects all conventional slabs-on-grade. The result: fewer joints (every 40-60 m instead of 5-6 m), flatness preserved over time, and maintenance costs reduced by 25-35% over 20 years. For warehouses and industrial floors, it is the most durable solution.
Does a post-tensioned ground slab still need joints?
Yes, but far fewer. A conventional slab-on-grade requires joints every 5-6 metres, amounting to approximately 200 linear metres of joints per 1,000 m². A post-tensioned slab needs them only every 40-60 metres — 8 to 10 times fewer joints. Each eliminated joint is one less weak point and one less maintenance expense.
What type of soil is suitable for a post-tensioned slab?
A post-tensioned slab adapts to all soil types, including poor soils (expansive clay, fill). Its stiffness and ability to redistribute loads make it more tolerant of differential settlement than a conventional slab. On very weak soils, it can be combined with ground treatment or rigid inclusions. BEPCO systematically carries out a geotechnical survey before design.
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