ASTM Certified Soils Technician
Examination Practice Questions &
[Verified Answers], Plus Explained
Rationales|2026 Latest Update| Instant
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1. In soil classification testing, the primary purpose of determining
grain-size distribution is to evaluate:
A. Soil color and mineral composition
B. The percentage of soil particles within different size ranges
C. The chemical reactivity of soil minerals
D. The organic content of soil only
Answer: B. The percentage of soil particles within different size ranges
Rationale: Grain-size distribution testing determines the relative
amounts of gravel, sand, silt, and clay-sized particles in a soil sample.
This information is essential for classification, compaction evaluation,
and predicting engineering behavior.
2. Which ASTM test method is commonly used for determining the
moisture content of soil by oven drying?
A. ASTM D4318
B. ASTM D698
C. ASTM D2216
D. ASTM D1557
,Answer: C. ASTM D2216
Rationale: ASTM D2216 covers laboratory determination of water
content of soils by mass using oven drying. Moisture content is critical
for compaction control and soil behavior analysis.
3. A soil technician performing a Proctor compaction test is primarily
determining:
A. Soil permeability
B. Maximum dry density and optimum moisture content
C. Soil mineralogy
D. Soil particle shape
Answer: B. Maximum dry density and optimum moisture content
Rationale: Compaction testing establishes the relationship between
moisture content and dry density, identifying the moisture level where
maximum compaction occurs.
4. The liquid limit of a soil represents the moisture content at which:
A. Soil changes from solid to semi-solid state
B. Soil changes from liquid to plastic state
C. Soil reaches maximum density
D. Soil becomes completely dry
Answer: B. Soil changes from liquid to plastic state
Rationale: The liquid limit is the boundary between liquid and plastic
consistency states and is used with the plastic limit to calculate the
plasticity index.
, 5. The plasticity index (PI) of a soil is calculated as:
A. Liquid limit minus plastic limit
B. Plastic limit minus liquid limit
C. Moisture content divided by dry density
D. Dry density minus wet density
Answer: A. Liquid limit minus plastic limit
Rationale: PI represents the range of moisture contents where soil
behaves plastically and is calculated as LL − PL.
6. A soil with a high plasticity index generally indicates:
A. High sand content
B. Low clay activity
C. Greater clay content and shrink-swell potential
D. Excellent drainage characteristics
Answer: C. Greater clay content and shrink-swell potential
Rationale: Highly plastic soils often contain significant clay minerals
that absorb water and change volume.
7. The primary purpose of soil compaction in construction is to:
A. Increase soil voids
B. Reduce soil strength
C. Increase density and improve engineering properties
D. Increase organic matter
Answer: C. Increase density and improve engineering properties
, Rationale: Compaction reduces air voids, increases strength, improves
stability, and reduces settlement potential.
8. In a field density test, the technician compares field dry density
with:
A. Soil color chart
B. Laboratory maximum dry density
C. Particle size distribution only
D. Liquid limit value
Answer: B. Laboratory maximum dry density
Rationale: Field compaction acceptance is commonly based on the
percentage of laboratory maximum dry density achieved in the field.
9. The sand cone test is used to determine:
A. Soil permeability
B. Field density and moisture content
C. Soil classification
D. Atterberg limits
Answer: B. Field density and moisture content
Rationale: The sand cone method measures the volume of an
excavation and the mass of soil removed to calculate in-place density.
10. A soil sample should be properly preserved before testing
because:
Examination Practice Questions &
[Verified Answers], Plus Explained
Rationales|2026 Latest Update| Instant
Download PDF
1. In soil classification testing, the primary purpose of determining
grain-size distribution is to evaluate:
A. Soil color and mineral composition
B. The percentage of soil particles within different size ranges
C. The chemical reactivity of soil minerals
D. The organic content of soil only
Answer: B. The percentage of soil particles within different size ranges
Rationale: Grain-size distribution testing determines the relative
amounts of gravel, sand, silt, and clay-sized particles in a soil sample.
This information is essential for classification, compaction evaluation,
and predicting engineering behavior.
2. Which ASTM test method is commonly used for determining the
moisture content of soil by oven drying?
A. ASTM D4318
B. ASTM D698
C. ASTM D2216
D. ASTM D1557
,Answer: C. ASTM D2216
Rationale: ASTM D2216 covers laboratory determination of water
content of soils by mass using oven drying. Moisture content is critical
for compaction control and soil behavior analysis.
3. A soil technician performing a Proctor compaction test is primarily
determining:
A. Soil permeability
B. Maximum dry density and optimum moisture content
C. Soil mineralogy
D. Soil particle shape
Answer: B. Maximum dry density and optimum moisture content
Rationale: Compaction testing establishes the relationship between
moisture content and dry density, identifying the moisture level where
maximum compaction occurs.
4. The liquid limit of a soil represents the moisture content at which:
A. Soil changes from solid to semi-solid state
B. Soil changes from liquid to plastic state
C. Soil reaches maximum density
D. Soil becomes completely dry
Answer: B. Soil changes from liquid to plastic state
Rationale: The liquid limit is the boundary between liquid and plastic
consistency states and is used with the plastic limit to calculate the
plasticity index.
, 5. The plasticity index (PI) of a soil is calculated as:
A. Liquid limit minus plastic limit
B. Plastic limit minus liquid limit
C. Moisture content divided by dry density
D. Dry density minus wet density
Answer: A. Liquid limit minus plastic limit
Rationale: PI represents the range of moisture contents where soil
behaves plastically and is calculated as LL − PL.
6. A soil with a high plasticity index generally indicates:
A. High sand content
B. Low clay activity
C. Greater clay content and shrink-swell potential
D. Excellent drainage characteristics
Answer: C. Greater clay content and shrink-swell potential
Rationale: Highly plastic soils often contain significant clay minerals
that absorb water and change volume.
7. The primary purpose of soil compaction in construction is to:
A. Increase soil voids
B. Reduce soil strength
C. Increase density and improve engineering properties
D. Increase organic matter
Answer: C. Increase density and improve engineering properties
, Rationale: Compaction reduces air voids, increases strength, improves
stability, and reduces settlement potential.
8. In a field density test, the technician compares field dry density
with:
A. Soil color chart
B. Laboratory maximum dry density
C. Particle size distribution only
D. Liquid limit value
Answer: B. Laboratory maximum dry density
Rationale: Field compaction acceptance is commonly based on the
percentage of laboratory maximum dry density achieved in the field.
9. The sand cone test is used to determine:
A. Soil permeability
B. Field density and moisture content
C. Soil classification
D. Atterberg limits
Answer: B. Field density and moisture content
Rationale: The sand cone method measures the volume of an
excavation and the mass of soil removed to calculate in-place density.
10. A soil sample should be properly preserved before testing
because:
