What is the recommended action if rain starts on a freshly placed slab?

• A. Cover the slab where rain is indenting the fresh surface
• B. Continue finishing as planned
• C. Remove all plastic sheets
• D. Apply additional curing compound

Answer: (A)

Fresh concrete is still plastic and vulnerable to damage from rain. Rain hitting the surface can wash away cement paste, create indentation or laitance, and lead to a rough, weak finish. The best action is to shield the areas being indented by rain with a waterproof covering, such as plastic sheets, to keep water off the surface while it’s still plastic. This targeted protection helps preserve the smoothness and integrity of the finish until the slab gains enough strength to resist damage. Continuing to work as rain falls risks smearing or washing the surface, removing coverings too early leaves more surface exposed, and applying curing compound during rain doesn’t address the immediate risk of washout.