CPII Materials & Testing 2 — Questions and Answers
Question 1: What does a slump test measure for freshly mixed concrete?
- Compressive strength
- Workability/consistency (Correct answer)
- Air content
- Water-cement ratio
Correct answer: Workability/consistency
The slump test measures the workability or consistency of fresh concrete before placement.
Question 2: Which ASTM standard governs the sampling of freshly mixed concrete?
- ASTM C31
- ASTM C172 (Correct answer)
- ASTM C39
- ASTM C138
Correct answer: ASTM C172
ASTM C172 covers the standard practice for sampling freshly mixed concrete.
Question 3: A proctor test (ASTM D698) is used to determine which soil property?
- Bearing capacity
- Shear strength
- Maximum dry density and optimum moisture content (Correct answer)
- Permeability
Correct answer: Maximum dry density and optimum moisture content
The standard proctor test establishes a soil's maximum dry density at its optimum moisture content.
Question 4: What is the minimum curing period for standard concrete test cylinders before compressive strength testing at 28 days?
- Cylinders must be moist-cured for the full 28 days (Correct answer)
- Cylinders can be air-dried after 24 hours
- Cylinders need only 7 days of moist curing
- No specific curing is required
Correct answer: Cylinders must be moist-cured for the full 28 days
Per ASTM C31, standard-cured cylinders must remain in moist conditions until the time of testing.
Question 5: Which test determines the resistance of coarse aggregate to abrasion and impact?
- Sand equivalent test
- Los Angeles abrasion test (Correct answer)
- Soundness test
- Flat and elongated test
Correct answer: Los Angeles abrasion test
The Los Angeles abrasion test (ASTM C131/C535) measures aggregate resistance to degradation by abrasion and impact.
Question 6: When inspecting a bituminous pavement core, what does a high air void content (above 8%) typically indicate?
- Over-compaction of the mat
- Potential for rutting under traffic
- Increased susceptibility to cracking and raveling (Correct answer)
- Better drainage characteristics
Correct answer: Increased susceptibility to cracking and raveling
Excessive air voids leave the asphalt mix permeable to water and oxidation, accelerating cracking and raveling.
Question 7: What is the purpose of the sand equivalent test for fine aggregate?
- Measure grain size distribution
- Determine the proportion of fine dust and clay-like material (Correct answer)
- Evaluate aggregate hardness
- Assess moisture absorption
Correct answer: Determine the proportion of fine dust and clay-like material
The sand equivalent test (ASTM D2419) indicates the relative proportion of detrimental fine dust or clay in fine aggregate.
CPII Materials & Testing 2
What does a slump test measure for freshly mixed concrete?