NETTCP Field Testing 3 — Questions and Answers
Question 1: A field technician performing a Clegg Impact Soil Tester (CIST) test obtains a Clegg Impact Value (CIV) well below the specification minimum. What does this likely indicate?
- The soil is over-compacted
- The soil stiffness is insufficient and additional compaction is needed (Correct answer)
- The moisture content is too low
- The test equipment needs recalibration
Correct answer: The soil stiffness is insufficient and additional compaction is needed
A low CIV indicates the soil lacks the required stiffness, typically meaning more compaction passes are needed before it meets specification.
Question 2: When sampling hot mix asphalt (HMA) from a truck for field quality control, samples should be taken from:
- The top center of the truckload
- Multiple locations across the truck bed, avoiding edges and top surface (Correct answer)
- Only the bottom of the load closest to the tailgate
- The freshly unloaded windrow on the paving mat
Correct answer: Multiple locations across the truck bed, avoiding edges and top surface
Sampling from multiple interior locations avoids the segregated, cooled surface material and provides a representative sample.
Question 3: During a field inspection, a technician notices transverse cracking at regular intervals on a newly placed asphalt overlay. The most likely cause is:
- Insufficient tack coat application
- Reflection cracking from underlying pavement joints (Correct answer)
- Over-compaction by the vibratory roller
- Contaminated aggregate in the mix
Correct answer: Reflection cracking from underlying pavement joints
Regularly spaced transverse cracks in an overlay typically reflect the joint pattern or pre-existing cracks from the underlying pavement layer.
Question 4: What is the primary purpose of applying a tack coat before placing an asphalt overlay?
- To waterproof the existing pavement surface
- To provide bond between the existing surface and the new overlay (Correct answer)
- To fill surface distresses before paving
- To cool the pavement before roller compaction
Correct answer: To provide bond between the existing surface and the new overlay
Tack coat (emulsified asphalt) creates adhesion between the existing pavement and the new HMA layer to prevent layer slippage.
Question 5: A technician is performing a field ride quality evaluation using an inertial profiler. What parameter does this device primarily measure?
- Pavement surface friction
- International Roughness Index (IRI) (Correct answer)
- Pavement cross-slope and superelevation
- Lane marking retroreflectivity
Correct answer: International Roughness Index (IRI)
An inertial profiler measures longitudinal pavement elevation profiles, which are processed to calculate the International Roughness Index (IRI).
Question 6: According to AASHTO standards, how many concrete cylinders should typically be cast per composite sample for compressive strength testing on a highway project?
- 1 cylinder per sample
- 2 cylinders per sample at minimum (Correct answer)
- 4 cylinders per sample
- 6 cylinders per sample
Correct answer: 2 cylinders per sample at minimum
AASHTO requires a minimum of two cylinders per composite sample so one can be tested at 28 days and one held for verification or early testing.
Question 7: When measuring pavement layer thickness in the field using a core sample, where should thickness be measured?
- At the widest visible point of the core
- Perpendicular to the top and bottom surfaces at multiple locations averaged (Correct answer)
- Only at the center of the core
- Along the longest diagonal of the core cross-section
Correct answer: Perpendicular to the top and bottom surfaces at multiple locations averaged
Thickness is measured perpendicular to the layer surfaces at several points around the core circumference and averaged for accuracy.
NETTCP Field Testing 3
A field technician performing a Clegg Impact Soil Tester (CIST) test obtains a Clegg Impact Value (CIV) well below the specification minimum.
What does this likely indicate?