How should laitance on the surface be addressed before finishing?

• A. Leave laitance in place and finish on top.
• B. Remove laitance by brushing or scarifying and re-finish to required finish.
• C. Apply curing compound to laitance.
• D. Install a new top layer without laitance removal.

Answer: (B)

Laitance must be removed before applying the finish because that creamy surface layer is weak and does not bond well to subsequent layers. It forms from the surface bleed water carrying fines to the top, creating a slick, cement-rich film that can dust, spall, or delaminate under traffic or finishing stresses. The proper approach is to mechanically remove it—brushing or scarifying—so the substrate is clean and sound, then re-finish to the required specification. Sealing laitance with a curing compound doesn’t fix the bonding issue and can trap the weak layer, while placing a new top layer without removing laitance leaves a weak interface that will not hold up.