What is scaling in concrete finishing and how can it be prevented?

• A. Scaling is flaking of the surface; prevent by proper curing, avoiding overworking, and ensuring adequate paste coverage.
• B. Scaling is surface cracking; prevent by adding more cement.
• C. Scaling is color change; prevent by pigments.
• D. Scaling is moisture loss; prevent by sealing.

Answer: (A)

Scaling is the flaking or peeling of the top surface of hardened concrete, caused when the surface paste is weak or poorly bonded to the aggregate. This usually happens if the concrete is finished too soon or with excessive force, and if curing is insufficient, so the surface skin isn’t able to develop properly and can break away under traffic or abrasion. Preventing it comes down to three essentials: proper curing to keep the surface moist long enough for the paste to hydrate and gain strength; avoiding overworking the surface during finishing, which can push out or loosen the surface paste and create laitance; and ensuring the surface has enough cement paste to bond with the aggregate, which often means appropriate mix design and finishing timing. The other choices describe different problems—surface cracking, color changes, or moisture loss—which are not what scaling refers to.