For the Modified Proctor, what is the required Maximum Density?

• A. 100%
• B. 102%
• C. 98%
• D. 95%

Answer: (C)

In compaction terminology, the field density is judged as a percent of the maximum dry density obtained from the test method used. When the Modified Proctor test is used, it defines a higher maximum dry density than the standard Proctor, because the energy applied in the Modified Proctor is greater.

Specifying a target of about 98% of that Modified Proctor maximum provides a practical, reliable standard for field compaction. It ensures the fill is dense enough to give good bearing capacity and stability, while remaining achievable in real-world conditions (moisture control, equipment, and variability in the material). Reaching exactly 100% of the maximum is typically not feasible in the field, and trying to exceed the test-defined maximum (like 102%) isn’t possible by definition. Values like 95% might be acceptable in other contexts or with different soils, but for many projects using the Modified Proctor, 98% is the commonly adopted target.

So the required maximum density used for field acceptance is 98% of the Modified Proctor maximum.