Chargement…
Chargement…
by Dakhla Aménagement Team
Shrinkage is the natural shortening of concrete as it hardens and dries. Direct answer: there are three shrinkages — plastic in the first hours, autogenous over weeks, drying over months — and the No. 1 remedy remains 7 days of moist curing; on the cement side, a fair dosage and controlled fineness limit the scale of the phenomenon.
| Type | Period | Order of magnitude | Main remedy |
|---|---|---|---|
| Plastic | First hours | Surface freshness, fine threads | Immediate wind and sun protection |
| Autogenous | Days to weeks | ~0.1 mm/m in ordinary concrete | Mix design: fair dosage, low W/C |
| Drying | Weeks to months | 0.3 to 0.6 mm/m if uncured | Extended moist curing |
These orders of magnitude are standard concrete-technology benchmarks, not product guarantees: the real value depends on dosage, aggregates, geometry and climate — in Dakhla, heat and wind dry the surface far faster than in temperate climates.
As soon as placing ends, bleed water evaporates. If evaporation outpaces water rising, the surface retracts while the core is still soft: fine threads appear. The remedy is three gestures: shelter from wind, mist-spray, cover — right after finishing, not in the evening.
Final shrinkage is above all that of the cement paste: more paste (overdosing), more shrinkage. A finer cement (high Blaine fineness) hydrates faster and demands more water at equal workability — hence plasticisers' value. And the hydration heat of a generous dosage creates thermal gradients that seed cracking on cooldown. The conclusion is counter-intuitive but solid: the most cracking-prone cement is often the one you put too much of.
Seven days of moist protection after pouring is the most profitable measure on site: it lets strength climb (the 2, 7 and 28-day tests prove it) while shrinkage proceeds unstrained. Periodic watering, polyane film, damp geotextile or curing compound — the principle is the same: don't let the surface dry before the concrete has gained strength.
Shrinkage alone does not crack: it cracks when restrained — by friction on a substrate, by rebars, by varying section shapes. That is the purpose of contraction joints (slabs: 4 to 6 m bays as common practice) and skin mesh: spread the deformation instead of concentrating it on a single crack.
Built with CPJ 45 or CPJ 55, your concrete starts with a controlled binder — quote within 24 h, delivered in Dakhla City.
Wind, sun, aridity: plastic shrinkage is decided in the first hour. Mist-spray, cover, protect.
Watering, film, damp geotextile: the site's most profitable measure against drying shrinkage.
≤ 0.50, plasticiser for workability: every extra litre of water swells shrinkage and costs 2-3 MPa.
Slabs: 4 to 6 m bays as common practice. A designed joint beats an endured crack.
Shrinkage cracks declare their nature within a week: fine and stable = monitoring, evolving = diagnosis.
Under sustained load, concrete deforms for years: 2 to 4 times the instantaneous deflection. Factors, consequences, and what belongs to the engineer.
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A concrete mix is designed to last 50 years, not to be redone: water/cement ratio, cover, curing and cement class — the levers that actually decide service life, especially on the coast.
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Read articleOur team responds within 24h. CPJ 45 on request, CPJ 55 on request. Delivery within Dakhla included.