NETTCP Asphalt Technology 2 — Questions and Answers
Question 1: What does the term 'viscosity' describe in relation to asphalt binders?
- The weight per unit volume of asphalt
- The resistance of asphalt to flow under applied stress (Correct answer)
- The temperature at which asphalt ignites
- The percentage of air voids in compacted mix
Correct answer: The resistance of asphalt to flow under applied stress
Viscosity measures an asphalt binder's resistance to flow, which directly affects mixing, compaction, and pavement performance.
Question 2: Which Superpave performance grade parameter addresses rutting resistance at high service temperatures?
- S (stiffness) at -18°C
- G*/sinδ at high temperature (Correct answer)
- m-value at low temperature
- Creep compliance at -24°C
Correct answer: G*/sinδ at high temperature
G*/sinδ (dynamic shear modulus divided by sine of phase angle) measured at high temperature indicates resistance to rutting.
Question 3: What is the primary purpose of a tack coat applied between pavement layers?
- To reduce reflective cracking
- To promote bonding between existing and new asphalt layers (Correct answer)
- To waterproof the subbase
- To improve skid resistance
Correct answer: To promote bonding between existing and new asphalt layers
Tack coats create an adhesive bond between layers, preventing slippage and delamination under traffic loads.
Question 4: In a Superpave mix design, what does the term 'Ndesign' represent?
- The number of mix trials required
- The number of gyrations used to compact the design specimen (Correct answer)
- The minimum number of cores taken from a completed project
- The nominal maximum aggregate size
Correct answer: The number of gyrations used to compact the design specimen
Ndesign is the number of gyratory compactor revolutions used to compact specimens to simulate expected traffic-level densification.
Question 5: Which aggregate property most directly affects the rutting resistance of an asphalt mix?
- Aggregate color
- Particle shape and angularity (Correct answer)
- Aggregate absorption capacity
- Thermal conductivity
Correct answer: Particle shape and angularity
Crushed, angular aggregates interlock more effectively than rounded particles, providing greater resistance to permanent deformation under load.
Question 6: What pavement distress is characterized by a series of closely spaced transverse cracks resembling alligator skin?
- Rutting
- Raveling
- Fatigue (alligator) cracking (Correct answer)
- Bleeding
Correct answer: Fatigue (alligator) cracking
Fatigue cracking, also called alligator cracking, results from repeated traffic loading that exceeds the pavement's structural capacity.
Question 7: Which test is used to measure the low-temperature cracking susceptibility of an asphalt binder?
- Rolling thin-film oven test (RTFO)
- Bending beam rheometer (BBR) (Correct answer)
- Dynamic shear rheometer at 64°C
- Softening point test
Correct answer: Bending beam rheometer (BBR)
The BBR measures creep stiffness and m-value of aged asphalt binder at low temperatures to predict thermal cracking resistance.
NETTCP Asphalt Technology 2
What does the term 'viscosity' describe in relation to asphalt binders?