NETTCP Lab Testing Procedures 2 — Questions and Answers
Question 1: When performing a Standard Proctor compaction test (AASHTO T 99), how many layers of soil are compacted into the mold?
- 2 layers
- 3 layers (Correct answer)
- 4 layers
- 5 layers
Correct answer: 3 layers
AASHTO T 99 requires 3 equal layers compacted with 25 blows of the 5.5-lb hammer per layer.
Question 2: In a sieve analysis of aggregates per AASHTO T 27, sieves must be arranged in the stack with the:
- Smallest opening at the top
- Largest opening at the top (Correct answer)
- Sieves in alphabetical order
- Sieves by weight, heaviest first
Correct answer: Largest opening at the top
Sieves are stacked largest opening at the top to smallest at the bottom, above the pan, so material is progressively retained on finer sieves.
Question 3: A concrete slump test per AASHTO T 119 measures which property of fresh concrete?
- Compressive strength
- Air content
- Workability/consistency (Correct answer)
- Water-cement ratio
Correct answer: Workability/consistency
The slump test measures the consistency (workability) of fresh concrete by recording how much the concrete slumps after the cone is removed.
Question 4: Which test method is used to determine the liquid limit of a fine-grained soil?
- AASHTO T 89 (Correct answer)
- AASHTO T 99
- AASHTO T 176
- AASHTO T 27
Correct answer: AASHTO T 89
AASHTO T 89 covers the determination of the liquid limit of soils using the Casagrande liquid limit device.
Question 5: When extracting asphalt content from a bituminous mixture using an ignition oven (AASHTO T 308), the test results give:
- Aggregate gradation only
- Binder content and aggregate gradation after washing (Correct answer)
- Only binder content by weight
- Voids in mineral aggregate
Correct answer: Binder content and aggregate gradation after washing
The ignition method burns off the asphalt binder, and the remaining aggregate can be sieved to provide both binder content and aggregate gradation.
Question 6: The purpose of curing concrete cylinders in a standard moist-curing room (AASHTO T 23) is to:
- Accelerate hydration by drying the surface
- Maintain humidity above 95% at 73°F to ensure proper hydration (Correct answer)
- Freeze and thaw cycles to test durability
- Reduce bleed water before testing
Correct answer: Maintain humidity above 95% at 73°F to ensure proper hydration
Standard curing at ≥95% relative humidity and 73±3°F ensures consistent hydration conditions for comparative compressive strength results.
Question 7: In a field density test using the sand-cone method (AASHTO T 191), what is the purpose of the Ottawa sand?
- To replace the excavated soil so the hole volume can be calculated (Correct answer)
- To stabilize the test hole during excavation
- To measure the moisture content of in-place material
- To determine the maximum dry density of the subgrade
Correct answer: To replace the excavated soil so the hole volume can be calculated
Ottawa sand of known density fills the excavated hole; measuring the sand used allows calculation of the hole's volume, which is then used to compute in-place density.
NETTCP Lab Testing Procedures 2
When performing a Standard Proctor compaction test (AASHTO T 99), how many layers of soil are compacted into the mold?