Bs En 12390-2:2019 Page

Cover the specimen immediately with a non-absorbent, airtight cover (e.g., plastic sheet or damp hessian if covered by plastic) to prevent moisture loss.
Store the moulded specimen in an environment at 20°C ± 5°C for the first 24 hours (for standard curing). Avoid drafts, direct sunlight, or vibration.

: Concrete is placed into moulds in layers and compacted using methods such as a vibrating table