The curing of concrete continues as long as its relative humidity remains above which percentage?

• A. 60 percent
• B. 90 percent
• C. 70 percent
• D. 80 percent

Answer: (D)

Curing is driven by ongoing hydration, which needs available moisture inside the concrete. This hydration can continue effectively only if the concrete remains sufficiently moist, which is indicated by relative humidity staying above eighty percent. When the RH drops below this level, moisture evaporates faster than it can be replenished, slowing or stopping the curing process and potentially reducing strength and durability. To ensure continuous curing, methods that keep the surface and interior moist—like moist curing, plastic coverings, or curing compounds—are used to maintain RH above eighty percent during the curing period.