Cravings on Concrete Surfaces - What, Why and How
Crazing on Concrete Surface – What, Why and How?

What is Crazing on a Concrete Surface?

Craving is the development of fine shallow hair cracks on the surface. The appearance of the concrete surface does not look so pleasant because of the madness. It may appear within a few days of treatment or sometimes after a longer period. These cracks do not penetrate deeply into the concrete and do not affect the structural strength of the concrete.

Why does crazing occur on concrete surfaces?

Shrinkage occurs due to drying or carbonation, or due to differential shrinkage between the concrete surface and the main body of the concrete. This differential shrinkage increases if the skin is richer than the original concrete. The drying shrinkage is greatest when the concrete dries rapidly after curing. So if care is not taken while curing, it will lead to crazing on the concrete surface.

How to stop crazing on concrete surface?

  1. Carefully fix the concrete surface, to extend the initial drying period as long as possible so that the shrinkage of the outer skin is consistent with the shrinkage of the main body of the concrete.
  2. Do not begin finishing work until the concrete is free of surface water. Troweling while still bleeding water on the surface will produce a high water-cement ratio and weaken the surface layer.
  3. Do not sprinkle cement over the surface to dry up the bleeding water as this concentrates the fines on the surface and can result in nuts.
  4. Use air-driven concrete with moderate deceleration. The air-penetration helps to reduce the bleeding rate of the fresh concrete and reduces the chances of fraying. Slump refers to the amount of water contained in the concrete. A high deceleration may allow the concrete mix to separate, resulting in a weak surface layer.
  5. Avoid excessive moisture gradient between the concrete surface and the interior.
  6. Trowel the surface as much as possible and especially avoid using a steel float.
  7. Avoid using rich facial mix, no more than 1:3 rich.
  8. Use as low a water-cement ratio as possible, to ensure adequate compaction.
  9. Avoid rubbing the surface with grouting procedures or clean cement paste.
  10. Avoid excessive vibration that results in too much slurry on the top or sides.

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.