What is the recommended procedure if a pour is interrupted by rain?

• A. Protect the surface, resume properly, and check slump/air after resuming; adjust curing as required.
• B. Ignore the disruption and proceed as planned.
• C. Skip the affected area and pour a long cure.
• D. Terminate the pour and start over after one day.

Answer: (A)

Rain during a concrete pour creates changes at the surface that can weaken the finish and alter the concrete’s properties. The best approach is to protect the exposed surface, resume the pour in a controlled way, then verify and adjust as needed. Protecting the surface helps prevent rapid evaporation, oversaturation, or contamination from debris, which keeps the concrete from developing surface flaws or laitance as it continues to hydrate. When you resume, do so in a way that maintains compaction and continuity with the already placed concrete, avoiding a loose or cold joint if possible. After resuming, check the fresh concrete’s slump and air content again because rain can dilute or wash away cement paste at the surface, changing workability and the internal air voids. If these tests show deviations from the spec, adjust curing to support proper hydration and surface durability—this might mean extended curing, applying protective coverings, or additional moisture retention measures. In short, protect the surface, resume with control, recheck material properties, and modify curing to ensure the final product meets specifications.