PIC Subbase Compaction Verification 4

Question 1

When should a paving inspector require a new Proctor test (reference standard) for subbase material?

Accepted Answer

When the source material or borrow pit changes significantly

Answer

A new Proctor is required when source material changes because different material compositions yield different optimum moisture and maximum density values.

Question 2

According to typical specifications, what is the maximum allowable lift thickness for granular subbase compaction?

Accepted Answer

6 to 8 inches loose measurement

Answer

Most highway specifications limit granular subbase lifts to 6–8 inches loose (compacting to roughly 5–6 inches) to ensure uniform compaction through the full depth.

Question 3

A nuclear density gauge must be calibrated against known standards. How often should field standardization checks be performed?

Accepted Answer

At the beginning of each work day

Answer

AASHTO and manufacturer guidelines require daily standardization checks against reference blocks to detect drift in gauge readings.

Question 4

Which roller type is MOST effective for compacting cohesive (clay) subbase materials?

Accepted Answer

Sheepsfoot or padfoot roller

Answer

Sheepsfoot/padfoot rollers knead and punch cohesive soils from the bottom up, achieving compaction that smooth drum rollers cannot in plastic materials.

Question 5

The 'one-point Proctor' method is used to:

Accepted Answer

Quickly estimate maximum dry density when material source is consistent

Answer

The one-point Proctor uses a correlation with a family of curves to estimate maximum dry density from a single test point, saving time when the source is established.

(PIC) Paving Inspector Certification Practice Test

(PIC) Paving Inspector Certification Practice Test

PIC Subbase Compaction Verification 4