Which of the following methods is NOT used in the process of compaction?

Compaction is a process used in various fields, particularly in engineering and construction, to increase the density of a material, usually soil or similar substances. The goal is to remove air voids, thereby improving the material's strength and stability.

The method of mixing primarily involves combining different materials to create a homogeneous mixture, but it does not directly contribute to compaction. Mixing is more concerned with the preparation of materials rather than the densification of existing materials.

On the other hand, vibration and tamping are both effective compaction techniques. Vibration uses mechanical forces to shake and compress the material, allowing particles to rearrange and settle into a denser configuration. Tamping employs a heavy weight or tool to compress the material downward, making it denser through repeated impacts.

Therefore, since mixing does not serve as a method for achieving compaction, it is identified as the answer that does not pertain to the compaction process.