KDOT Construction Materials Testing & Quality Control 2 — Questions and Answers
Question 1: When performing a sand equivalent test on a fine aggregate sample, what does a higher sand equivalent value indicate?
- More clay and fine dust content
- Cleaner aggregate with less plastic fines (Correct answer)
- Higher moisture absorption capacity
- Greater particle angularity
Correct answer: Cleaner aggregate with less plastic fines
A higher sand equivalent value indicates the aggregate is cleaner and contains fewer detrimental plastic fines and clay material.
Question 2: According to KDOT specifications, what is the minimum number of random samples required per lot for hot mix asphalt acceptance testing?
- 1 sample
- 2 samples
- 3 samples (Correct answer)
- 5 samples
Correct answer: 3 samples
KDOT requires a minimum of 3 random samples per lot to establish statistical validity for HMA acceptance decisions.
Question 3: During concrete placement, a slump test result of 0 inches on a mix designed for 3-inch slump most likely indicates:
- Water was added at the site
- Excessive admixture dosage
- Mix is too dry or has lost workability (Correct answer)
- Incorrect aggregate gradation
Correct answer: Mix is too dry or has lost workability
A slump of 0 inches on a mix designed for 3 inches typically indicates the concrete is too stiff, possibly due to insufficient water or loss of workability during transport.
Question 4: What laboratory method is used to determine the plastic limit of a soil?
- Rolling soil into 1/8-inch diameter threads until they crumble (Correct answer)
- Penetrating soil with a cone penetrometer
- Compacting soil in a 4-inch mold at standard effort
- Measuring moisture content at field capacity
Correct answer: Rolling soil into 1/8-inch diameter threads until they crumble
The plastic limit is determined by rolling soil into 1/8-inch (3.2 mm) diameter threads and noting the moisture content at which threads begin to crumble.
Question 5: A proctor compaction test yields a maximum dry density of 118 pcf. Field nuclear gauge readings show 115.8 pcf. What is the percent compaction?
- 96.5%
- 97.0%
- 98.1% (Correct answer)
- 101.9%
Correct answer: 98.1%
Percent compaction = (115.8 / 118) × 100 = 98.1%, which meets typical KDOT embankment requirements.
Question 6: Which AASHTO test method governs the tensile splitting strength of cylindrical concrete specimens?
- AASHTO T 22
- AASHTO T 177
- AASHTO T 198 (Correct answer)
- AASHTO T 231
Correct answer: AASHTO T 198
AASHTO T 198 covers the splitting tensile strength of cylindrical concrete specimens, also known as the Brazilian split test.
Question 7: What does the term 'deleterious materials' refer to in aggregate quality testing?
- Aggregates with high specific gravity values
- Harmful substances like clay lumps, soft particles, or coal that degrade performance (Correct answer)
- Aggregates exceeding maximum size limits
- Rounded particles that reduce internal friction
Correct answer: Harmful substances like clay lumps, soft particles, or coal that degrade performance
Deleterious materials are harmful substances such as clay lumps, friable particles, coal, lignite, and other soft materials that reduce aggregate durability and concrete/asphalt performance.
KDOT Construction Materials Testing & Quality Control 2
When performing a sand equivalent test on a fine aggregate sample, what does a higher sand equivalent value indicate?