KDOT Asphalt & Concrete Paving Inspection 2 — Questions and Answers
Question 1: What is the minimum number of cores that KDOT typically requires for density verification on an asphalt lot?
- 1 core per lot
- 2 cores per lot
- 3 cores per lot (Correct answer)
- 5 cores per lot
Correct answer: 3 cores per lot
KDOT specifications generally require a minimum of 3 cores per lot to statistically represent density across the paved area.
Question 2: During hot-mix asphalt (HMA) placement, the inspector notices the mix is arriving at the paver at 260°F. What action should be taken?
- Accept the load; temperature is within typical range
- Reject the load; mix is overheated and may be burned (Correct answer)
- Request additional compaction passes to compensate
- Add water to cool the mix before placement
Correct answer: Reject the load; mix is overheated and may be burned
HMA delivered above the maximum mixing/lay-down temperature (typically around 325°F, but 260°F can be project-specific; if it exceeds the JMF maximum, the load is rejected) — inspectors must reject burned or overheated mix that fails temperature specs.
Question 3: Which concrete curing method is generally considered most effective for preventing plastic shrinkage cracking?
- Burlap dry curing
- White-pigmented curing compound applied immediately after finishing (Correct answer)
- Polyethylene sheeting placed 4 hours after placement
- Air-curing with no cover
Correct answer: White-pigmented curing compound applied immediately after finishing
White-pigmented curing compound applied immediately after the bleed water sheen disappears reflects sunlight and seals moisture, minimizing plastic shrinkage cracking.
Question 4: An inspector measures the longitudinal joint offset between two adjacent asphalt layers and finds them aligned directly over each other. This is:
- Acceptable practice for maximum bond strength
- Non-compliant; joints should be offset by at least 6 inches between layers (Correct answer)
- Non-compliant; joints must be offset by at least 18 inches between layers
- Acceptable only if both layers are the same mix type
Correct answer: Non-compliant; joints should be offset by at least 6 inches between layers
KDOT requires longitudinal joints to be offset by at least 6 inches (150 mm) between successive lifts to prevent a continuous plane of weakness.
Question 5: What does the term 'mat temperature differential' refer to during asphalt paving inspections?
- The difference between air temperature and asphalt delivery temperature
- The temperature variation across the width of the paved mat behind the screed (Correct answer)
- The difference between base course and surface course temperatures
- The cooling rate of asphalt after compaction is complete
Correct answer: The temperature variation across the width of the paved mat behind the screed
Mat temperature differential is the variation in mix temperature measured laterally across the mat width, which can indicate segregation or screed heating problems.
Question 6: Portland cement concrete (PCC) pavement inspector observes 'D-cracking' in an existing roadway being used as a reference. D-cracking is caused by:
- Overloading during the first winter after construction
- Freeze-thaw deterioration of frost-susceptible coarse aggregate (Correct answer)
- Excess water added to the mix during placement
- Inadequate joint sawing depth
Correct answer: Freeze-thaw deterioration of frost-susceptible coarse aggregate
D-cracking results from freeze-thaw cycles that cause frost-susceptible (porous) coarse aggregate to expand, creating characteristic 'D'-shaped crack patterns near joints.
Question 7: When checking concrete pavement surface smoothness with a 10-foot straightedge, what is the typical KDOT maximum allowable deviation?
- 1/8 inch
- 3/16 inch
- 1/4 inch (Correct answer)
- 3/8 inch
Correct answer: 1/4 inch
KDOT standard specifications typically allow a maximum deviation of 1/4 inch (6 mm) under a 10-foot straightedge for concrete pavement surface smoothness.
KDOT Asphalt & Concrete Paving Inspection 2
What is the minimum number of cores that KDOT typically requires for density verification on an asphalt lot?