Which of the following properties is NOT appropriate for the slump test mold's surface?

The slump test mold is designed to assess the workability and consistency of fresh concrete. For effective performance, the surface of the mold must have specific characteristics that allow for consistent results.

A rough surface is not suitable for the slump test mold because it can cause the concrete to adhere unevenly, leading to inaccurate measurements. The mold's surface is intended to be smooth and non-absorbent to ensure that the concrete can slide off easily without sticking, which could affect the height of the slump measurement. A flat surface facilitates an even base for the concrete, allowing for a consistent and reliable reading.

Moisture on the surface is acceptable since it can help to prevent the concrete from sticking, but overall, the ideal conditions for the slump test involve a non-absorbent, flat, and clean surface that minimizes variance in test results. Thus, selecting a smooth rather than rough surface is critical for the test's integrity.