NETTCP Soils and Aggregates 4

Question 1

Which compaction test method uses a 10-lb hammer dropped 18 inches and is commonly specified for highway subgrade?

Accepted Answer

Modified Proctor (AASHTO T 180)

Answer

The Modified Proctor test uses a 10-lb (4.54 kg) hammer with an 18-inch drop and higher compactive effort, simulating modern heavy compaction equipment.

Question 2

The plasticity index (PI) is calculated as:

Accepted Answer

Liquid limit minus plastic limit

Answer

Plasticity index equals liquid limit minus plastic limit and represents the range of moisture content over which a soil behaves plastically.

Question 3

A nuclear density gauge used for field compaction testing measures:

Accepted Answer

In-place wet density and moisture content simultaneously

Answer

Nuclear density gauges use gamma radiation and neutron scatter to simultaneously measure in-place wet density and moisture content of compacted material.

Question 4

What is the primary purpose of lime stabilization in subgrade soils?

Accepted Answer

Reduce plasticity and improve strength of high-plasticity clays

Answer

Lime reacts with clay particles through pozzolanic and cation exchange reactions to reduce plasticity index and improve strength and stability.

Question 5

During a sieve analysis, the cumulative percent retained on a sieve is used to calculate:

Accepted Answer

Fineness modulus and percent passing

Answer

Cumulative percent retained values are used to compute percent passing each sieve and to calculate the fineness modulus for fine aggregates.

(NETTCP) New England Transportation Technician Certification Program Practice Test

(NETTCP) New England Transportation Technician Certification Program Practice Test

NETTCP Soils and Aggregates 4