NETTCP Field Testing 5 — Questions and Answers
Question 1: A field technician is conducting a straight-edge test on a newly paved asphalt surface. A 10-foot (3 m) straightedge is placed parallel to the centerline. The maximum allowable deviation under the straightedge per most New England DOT specs is:
- 1/8 inch (3 mm)
- 3/16 inch (5 mm)
- 1/4 inch (6 mm) (Correct answer)
- 1/2 inch (13 mm)
Correct answer: 1/4 inch (6 mm)
Most New England DOT specifications allow a maximum deviation of 1/4 inch (6 mm) under a 10-foot straightedge for finished asphalt surfaces.
Question 2: During culvert installation inspection, a field technician finds that the bedding material under a corrugated metal pipe does not extend the full pipe width. This deficiency will most likely cause:
- Reduced flow capacity due to pipe deflection
- Corrosion of the pipe invert
- Differential settlement and uneven load distribution (Correct answer)
- Premature joint separation at the outlet end
Correct answer: Differential settlement and uneven load distribution
Inadequate bedding support creates uneven load transfer, leading to differential settlement, pipe distortion, and potential failure over time.
Question 3: What field test is used to evaluate the surface friction characteristics of a wet pavement using a locked-wheel trailer?
- Sand Patch Test (ASTM E965)
- Skid Resistance Test (ASTM E274) (Correct answer)
- Texture Depth Test (ASTM E1845)
- Profilograph Index Test (Caltrans method)
Correct answer: Skid Resistance Test (ASTM E274)
ASTM E274 uses a locked-wheel skid trailer towed at 40 mph on a wetted pavement to measure the friction number as a Skid Number (SN).
Question 4: A technician is sampling aggregate from a stockpile for gradation testing. To obtain a representative sample, the technician should:
- Scoop material only from the top center of the pile
- Collect multiple increments from various locations and depths, then quarter down (Correct answer)
- Take a single large sample from the base of the pile
- Select material from the visible surface at three evenly spaced points
Correct answer: Collect multiple increments from various locations and depths, then quarter down
Stockpiles segregate by particle size during placement; collecting multiple increments from varied locations and reducing by quartering gives a representative sample.
Question 5: During a field inspection of reinforcing steel placement, a technician measures 2-inch (50 mm) clear cover where the plan requires 3 inches (75 mm). The appropriate action is:
- Accept it since the difference is within typical construction tolerance
- Document the nonconformance and require the contractor to correct before concrete placement (Correct answer)
- Increase concrete strength to compensate for reduced cover
- Allow placement to proceed since cover will increase with concrete settlement
Correct answer: Document the nonconformance and require the contractor to correct before concrete placement
Inadequate rebar cover reduces corrosion protection and must be corrected before concrete is placed, as the deficiency cannot be remedied afterward.
Question 6: When performing field compaction testing on granular base course using the nuclear density gauge in the backscatter mode, what is being measured?
- Only the moisture content of the top 2 inches of material
- Density and moisture of the top 2–3 inches of material (Correct answer)
- Full-depth density from surface to 12 inches
- Density of material at a fixed depth of 6 inches
Correct answer: Density and moisture of the top 2–3 inches of material
Backscatter mode measures gamma radiation reflected from the top 2–3 inches of the surface layer and is suitable only for thin layers or surface evaluation.
Question 7: A field technician observes that the contractor's paver screed is leaving a coarse, rough texture on the asphalt mat surface. The most likely cause is:
- Excessive screed angle of attack (too high)
- Mix temperature too low causing material to tear rather than flow under the screed (Correct answer)
- Too much tack coat applied to the existing surface
- Roller pattern not overlapping sufficiently during breakdown rolling
Correct answer: Mix temperature too low causing material to tear rather than flow under the screed
When HMA is too cold, it loses workability and tears under the screed rather than flowing smoothly, resulting in a coarse, raveled surface texture.
NETTCP Field Testing 5
A field technician is conducting a straight-edge test on a newly paved asphalt surface.
A 10-foot (3 m) straightedge is placed parallel to the centerline.
The maximum allowable deviation under the straightedge per most New England DOT specs is: