PIC Paving Procedures & Equipment Operation 2 — Questions and Answers
Question 1: What is the primary purpose of a vibratory screed on an asphalt paver?
- To heat the mat surface
- To consolidate and level the asphalt mat before compaction (Correct answer)
- To distribute aggregate evenly through the mix
- To measure mat thickness continuously
Correct answer: To consolidate and level the asphalt mat before compaction
The vibratory screed pre-consolidates and strikes off the asphalt mat to the desired thickness and initial density before roller compaction begins.
Question 2: When a paving inspector observes 'fat spots' or shiny areas in the asphalt mat, what is the most likely cause?
- Excessive compaction effort
- Segregation or excess asphalt binder accumulation (Correct answer)
- Insufficient roller passes
- Low mix temperature
Correct answer: Segregation or excess asphalt binder accumulation
Fat spots indicate areas where excess binder has risen to the surface, often caused by mix segregation or improper mix design with too high a binder content.
Question 3: At what minimum temperature should a breakdown roller typically begin compacting a standard dense-graded HMA mat?
- 175°F (79°C)
- 225°F (107°C)
- 275°F (135°C) (Correct answer)
- 325°F (163°C)
Correct answer: 275°F (135°C)
Breakdown rolling should begin as soon as possible after placement, typically when the mat temperature is at or above 275°F (135°C) to achieve proper compaction.
Question 4: Which paver component controls the auger speed and is critical for maintaining a consistent head of material?
- The push rollers
- The hopper wings
- The material feed system (conveyor/auger controls) (Correct answer)
- The screed extension plates
Correct answer: The material feed system (conveyor/auger controls)
The material feed system, including conveyor and auger controls, regulates how much mix is delivered to maintain a consistent head of material in front of the screed.
Question 5: What type of roller is best suited for the finish rolling phase of HMA compaction?
- Vibratory steel drum roller
- Pneumatic tire roller
- Static steel tandem roller (Correct answer)
- Padfoot roller
Correct answer: Static steel tandem roller
Static steel tandem rollers are used during finish rolling to remove any roller marks and achieve a smooth final surface without risk of displacement.
Question 6: A paving inspector notices the mat has a 'tearing' texture rather than a smooth surface. What paving equipment condition most likely causes this?
- Screed temperature is too high
- Paver travel speed is too fast for the material supply (Correct answer)
- Roller is operating in vibration mode during finish pass
- Truck transfer is occurring too slowly
Correct answer: Paver travel speed is too fast for the material supply
A tearing texture typically occurs when the paver moves faster than material can be supplied, causing the screed to drag and tear the mat rather than float smoothly.
Question 7: What does the term 'mat segregation' refer to in asphalt paving?
- Separation of asphalt layers due to inadequate tack coat
- Non-uniform distribution of aggregate particle sizes across the mat (Correct answer)
- Temperature differences between adjacent paving lanes
- Cracking along longitudinal joints
Correct answer: Non-uniform distribution of aggregate particle sizes across the mat
Mat segregation is the non-uniform distribution of coarse and fine aggregate particles in the mat, which creates areas of differing density and texture that reduce pavement performance.
PIC Paving Procedures & Equipment Operation 2
What is the primary purpose of a vibratory screed on an asphalt paver?