The Compaction Factor Apparatus is a laboratory testing device used in civil engineering to measure the workability of fresh concrete mixes, particularly those with low workability (e.g., stiff mixes that are compacted by vibration rather than free fall). It determines the compaction factor, which is the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete in a standard container. This test is more precise and sensitive than the slump test for low-workability concrete and is applicable both in labs and the field.