Soil compaction removes air voids from soil, increasing its density and load-bearing capacity. It's required before pouring foundations, roads, and slabs.
Testing
- Proctor test: Determines maximum dry density and optimum moisture content
- Nuclear density gauge: Field testing for compaction percentage
- Target: typically 95% Standard Proctor for fill, 98% for structures
Compaction Factor
Loose soil → compacted: Clay shrinks ~25%. Gravel shrinks ~10–12%. You need more loose fill than the final compacted volume.