What happens if finishing steps are performed before the previous set?

• A. It may cause tearing, laitance, surface crazing, or pull-out of cream
• B. It will not affect quality
• C. It will improve surface finish
• D. It will reduce curing time

Answer: (A)

Finishing before the previous set is complete means you’re working on a surface that is still plastic and not yet stiff enough to support additional work. The trowel or finish tool then pushes and scrapes the surface, which pushes up and exposes the soft, cement-paste that has risen to the top with bleed water. This creates a weak, powdery layer called laitance, which can peel off and ruin the surface’s hardness and bonding for toppings.

Tearing can occur because the surface hasn’t gained enough strength to resist the knife-like action of the finishing tools, pulling apart the thin outer layer and leaving rough, irregular patches. The “cream” or creamy top layer—the smoother, paste-rich skin—can be pulled away with the finishing motion, leaving a rough, uneven finish and compromising durability.

Surface crazing, or fine crack patterns, can result from overworking the surface while it’s still adjusting and with moisture still present, especially if finishing is done prematurely. All of these effects degrade the appearance and long-term performance of the slab.

In contrast, waiting for the concrete to reach initial set and then finishing helps embed aggregates properly, minimizes laitance, reduces the chance of pulling out the creamy surface, and yields a smoother, stronger finish. The other options suggest no effect or a benefit, but premature finishing actually harms surface quality and durability.