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Slab Curing Mistakes

Slab Curing Mistakes – What Commonly Happens on Site

Small curing mistakes in the first 24–48 hours decide whether a slab stays strong or develops hairline cracks and weak surface layers later.

On many residential sites, slab curing is treated as a routine task—water is poured once or twice and assumed to be enough. In reality, early moisture loss and heat/wind exposure can trigger shrinkage cracks and a brittle, dusting top layer.

Q1: Why is slab curing often taken lightly?

  • Once the slab is cast, many teams consider the job “over” and move on to shutters/cleanup.
  • Water is sprinkled to show activity, not to retain moisture continuously.
  • Curing sometimes starts only the next day, after the surface has already dried.
  • Myth: “It’s already set; it will gain strength automatically.”

Site Note: Slabs dry faster in the first few hours due to heat and wind—this is when shrinkage marks begin.

Q2: What happens if curing is delayed or casual?

  • Surface dries and forms a thin brittle skin.
  • Hairline cracks develop from shrinkage and thermal movement.
  • Top layer loses density—leads to dusting and weak bonding for future finishes.
  • During waterproofing/plastering, this weak layer can delaminate easily.

Observation: Sun-exposed bays heat up more and crack more if not kept moist continuously.

Q3: When should curing actually start after casting?

  • Don’t wait a full day—slab starts shrinking much earlier.
  • Begin as soon as finishing is complete and surface can be kept moist without damage.
  • Keep the slab continuously moist in the early period; avoid “wet-dry-wet” cycles.

Site Check: If poured water disappears quickly, the surface is drying more than it should—step up retention.

Q4: Common curing methods and what usually goes wrong

  • Sprinkling only: Quick splash dries in minutes—no moisture retention.
  • Ponding without bunds: Water runs off edges; corners stay dry.
  • Wet jute/hessian not re-wetted: Acts like a wick and pulls moisture out if left to dry.
  • Curing compounds misused: Sprayed once and forgotten; edges/joints not covered; applied on dusty surface, so film doesn’t seal.
  • No wind/sun protection: Direct sun + wind early on accelerates drying and cracking.

Correct Curing Checklist (Practical)

  • Finish surface, then start curing as early as it can safely hold water/coverings.
  • Provide low bunds at slab perimeter and around columns/openings to enable ponding.
  • Keep continuously moist; re-wet hessian before it dries. Avoid alternation between dry and wet.
  • Use curing compound where ponding is impractical (ramp edges, difficult zones). Clean dust before application and cover edges/joints.
  • Shade sun-exposed zones; break wind with temporary screens if feasible.
  • Maintain adequate curing duration (don’t stop after two days). Extend in hot/dry weather.

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