PIC Subbase Compaction Verification 2

Question 1

A nuclear density gauge reads a wet density of 128.5 pcf and a moisture content of 6.2%. What is the dry density?

Accepted Answer

121.0 pcf

Answer

Dry density = wet density / (1 + moisture fraction) = 128.5 / 1.062 ≈ 121.0 pcf.

Question 2

Which condition would cause a sand cone test to yield an artificially LOW density result?

Accepted Answer

Sand spilling into voids adjacent to the test hole

Answer

If sand escapes into side voids beyond the actual hole volume, the calculated hole volume is overstated, producing a falsely low density.

Question 3

The term 'relative compaction' is best defined as:

Accepted Answer

Field dry density divided by maximum laboratory dry density, expressed as a percentage

Answer

Relative compaction (%) = (field dry density / max lab dry density) × 100, indicating how well field compaction matches the lab standard.

Question 4

When using a Clegg impact soil tester, a higher Clegg Impact Value (CIV) indicates:

Accepted Answer

Greater soil stiffness and compaction

Answer

A higher CIV reflects greater resistance to the falling hammer, indicating stiffer, more compact material.

Question 5

A subbase layer fails compaction testing at 91% when 95% is specified. The FIRST corrective action should be:

Accepted Answer

Scarify, adjust moisture if needed, and re-compact

Answer

Scarifying and re-compacting after moisture adjustment is the standard first step before considering material removal.

(PIC) Paving Inspector Certification Practice Test