NETTCP Quality Control 5 — Questions and Answers
Question 1: Under NETTCP quality control protocols, what action should a technician take if a concrete air content test result falls outside the specified range?
- Immediately notify the inspector and document the result before any concrete is placed (Correct answer)
- Allow placement to continue and retest the next load
- Adjust the admixture dosage on the truck and retest without notifying anyone
- Reject the entire truck without further testing
Correct answer: Immediately notify the inspector and document the result before any concrete is placed
Out-of-specification results must be immediately reported and documented so the inspector can make an informed disposition decision before placement proceeds.
Question 2: What is the primary reason aggregate used in asphalt mixtures must meet flat and elongated particle limits?
- Flat and elongated particles are prone to breaking under compaction and traffic loads (Correct answer)
- They increase the void content of the mixture too much
- They cause excessive absorption of asphalt binder
- They reduce the adhesion between aggregate and binder
Correct answer: Flat and elongated particles are prone to breaking under compaction and traffic loads
Flat and elongated particles have high aspect ratios that make them susceptible to fracturing during mixing, compaction, and under repeated traffic loading.
Question 3: What is the purpose of the Hamburg Wheel Track test for asphalt mixtures?
- To evaluate rutting resistance and moisture susceptibility simultaneously (Correct answer)
- To determine the optimum asphalt content of the mix
- To measure the tensile strength of the compacted mixture
- To assess the compactibility of the mix design
Correct answer: To evaluate rutting resistance and moisture susceptibility simultaneously
The Hamburg Wheel Track test subjects submerged HMA specimens to a steel wheel to simultaneously evaluate rutting resistance and stripping potential.
Question 4: A split sample is sent to both the contractor's QC lab and the agency's QA lab. The results differ significantly. What is the correct protocol?
- Request referee testing from an independent accredited laboratory (Correct answer)
- Use the agency's result as the binding result without further action
- Average the two results and use that value for payment
- Accept the contractor's result since they own the QC program
Correct answer: Request referee testing from an independent accredited laboratory
When split sample results conflict significantly, referee testing by an independent, accredited laboratory is the accepted protocol for resolving disputes.
Question 5: What does the term 'lot' mean in the context of highway construction quality control?
- A defined quantity of material or area of work used as the basis for acceptance testing (Correct answer)
- The total volume of material produced for an entire project
- A single truckload of concrete or asphalt
- The daily production from a plant or quarry
Correct answer: A defined quantity of material or area of work used as the basis for acceptance testing
A lot is a specified quantity of material (by tonnage, area, or volume) or a defined work unit upon which statistical acceptance decisions are based.
Question 6: Which condition would cause a QC technician to suspend concrete sampling operations at a bridge deck pour?
- Ambient air temperature drops below 40°F and no cold weather protection plan is in place (Correct answer)
- Concrete slump is at the low end but within specification
- Truck wait time exceeds 30 minutes at the pump
- The air content is 0.5% above the target value
Correct answer: Ambient air temperature drops below 40°F and no cold weather protection plan is in place
Concrete placement must stop or cold weather protection measures must be in place when temperatures fall below 40°F because hydration slows dramatically and freezing can damage fresh concrete.
Question 7: What is the maximum allowable time between water addition and completion of discharge for a ready-mix concrete truck, per ASTM C 94?
- 90 minutes or 300 drum revolutions, whichever comes first (Correct answer)
- 60 minutes regardless of drum revolutions
- 120 minutes if the concrete temperature is below 80°F
- 45 minutes from the time of batching
Correct answer: 90 minutes or 300 drum revolutions, whichever comes first
ASTM C 94 limits ready-mix concrete delivery to 90 minutes or 300 revolutions of the drum after introduction of water, whichever occurs first.
NETTCP Quality Control 5
Under NETTCP quality control protocols, what action should a technician take if a concrete air content test result falls outside the specified range?