Laitance definition and effect.

• A. Laitance is a protective film that improves surface durability.
• B. Laitance is a pigment added to the surface for texture.
• C. Laitance is a thick sealant layer that waterproofs the surface.
• D. Laitance is a fine cement paste that can appear on the surface if overworking; preventing by proper curing and avoiding excessive abrasion.

Answer: (D)

Laitance is a thin, weak layer of cement paste that rises to the surface during finishing when there’s excess bleed water and fines being carried upward, especially if the surface is overworked or not properly cured. This film is softer and bonded only weakly to the bulk concrete, so it can dust off, spall, and prevent coatings or toppings from bonding well.

The best defense is to manage curing and finishing practices: use proper curing to control evaporation, avoid excessive or early abrasion of the surface, and delay aggressive finishing that pushes fines to the top. If laitance is already present, it should be removed mechanically (light grinding or brushing) before applying overlays or sealers.

This isn’t a protective film, a pigment, or a waterproof sealant. It’s a weak cement paste that compromises surface performance, which is why the described prevention and removal approach matters.