What will the Engineer do when a QC computed dry density results in a value greater than 105% of the applicable Proctor maximum dry density?

• A. The Engineer will ignore it
• B. The Engineer will increase compaction
• C. The Engineer will perform an Independent Verification density test within 5 ft
• D. The Engineer will mix in additional moisture

Answer: (C)

When a QC dry density result is above 105% of the Proctor maximum dry density, the test results are treated as suspect and an independent check is required. The engineer orders an Independent Verification density test to confirm the density value and ensure the lift actually meets the project specifications, rather than relying on a potentially biased or erroneous QC reading. This verification is typically done within a short distance—often within five feet—to compare measurements on the same lift and area. This approach protects against accepting an over-dense or inaccurate result and ensures proper compaction control. Ignoring the result or simply increasing moisture or compaction would not resolve a possible measurement error and could lead to noncompliant or uneven ground.