What is the difference between Standard and Modified compaction?
Standard laboratory compaction, ASTM D 698, AASHTO T 99. Modified laboratory compaction, ASTM D 1557, AASHTO T 150, The Modified Compaction method requires 4.5 times more effort than required by the Standard Compaction method. It therefore densifies the soil to a greater degree, reducing the air voids and increasing the in-place density by a nominal 5% over that attained by using the Standard Compaction effort. The Modified Compaction method is required where foundations are to be placed in the soil backfill, and where minimal or no settlement can be tolerated by the structure.
