NETTCP Asphalt Technology 4 — Questions and Answers
Question 1: What does the Superpave performance grade designation PG 70-28 indicate?
- The binder passes high-temp tests at 70°C and low-temp tests at -28°C (Correct answer)
- The mix has 70% aggregate and 28% filler
- The binder softening point is 70°F and flash point is 28°C
- The mix passes Marshall stability at 70 kN and 28 blows
Correct answer: The binder passes high-temp tests at 70°C and low-temp tests at -28°C
Superpave PG grades specify the maximum pavement temperature (70°C) and minimum pavement temperature (-28°C) at which the binder meets performance requirements.
Question 2: Which test measures the resistance of compacted asphalt specimens to deformation under repeated loading, simulating traffic?
- Hamburg wheel-track test (Correct answer)
- Cantabro loss test
- Tensile strength ratio (TSR) test
- Rolling thin-film oven test
Correct answer: Hamburg wheel-track test
The Hamburg wheel-track test rolls a steel wheel over submerged, compacted specimens to measure rutting depth and stripping susceptibility.
Question 3: What is the main purpose of a prime coat applied to an untreated base course?
- To seal the surface against moisture before winter
- To penetrate and bind the base surface and promote adhesion of HMA (Correct answer)
- To add structural strength to the pavement section
- To reduce reflective cracking from the base
Correct answer: To penetrate and bind the base surface and promote adhesion of HMA
Prime coats penetrate granular bases, binding loose particles and providing a bonding surface for the overlying asphalt layer.
Question 4: What pavement distress is identified by longitudinal depressions in the wheel paths caused by plastic deformation?
- Shoving
- Rutting (Correct answer)
- Depression
- Corrugation
Correct answer: Rutting
Rutting is permanent longitudinal deformation in the wheel paths resulting from repeated traffic loads causing plastic flow in the asphalt layers.
Question 5: Which specification governs the gradation requirements for aggregates used in Superpave mix design?
- Control points and restricted zone (now optional) on the 0.45-power gradation chart (Correct answer)
- ASTM C131 sieve analysis requirements
- Marshall design chart gradation bands
- AASHTO T 27 standard sieve series only
Correct answer: Control points and restricted zone (now optional) on the 0.45-power gradation chart
Superpave uses control points and the 0.45-power gradation chart to ensure aggregate gradation passes through specified limits for proper mix performance.
Question 6: What does 'VMA' stand for in asphalt mix design, and why is it important?
- Void Mixture Aggregate — controls mix density only
- Voids in the Mineral Aggregate — the total void space among aggregate particles, including air voids and binder (Correct answer)
- Volume of Mixed Asphalt — total volume of compacted mix
- Viscosity-Modified Asphalt — type of polymer-modified binder
Correct answer: Voids in the Mineral Aggregate — the total void space among aggregate particles, including air voids and binder
VMA represents the total void space in the aggregate skeleton; adequate VMA ensures enough room for asphalt binder plus air voids, which is essential for durability.
Question 7: What is the purpose of the rolling thin-film oven test (RTFO) on asphalt binders?
- To measure binder viscosity at mixing temperature
- To simulate short-term aging of binder during plant production and compaction (Correct answer)
- To measure binder performance at low temperatures
- To determine binder flash point for safety compliance
Correct answer: To simulate short-term aging of binder during plant production and compaction
The RTFO exposes thin binder films to heat and airflow, simulating the aging and hardening that occurs during hot-mix plant production.
NETTCP Asphalt Technology 4
What does the Superpave performance grade designation PG 70-28 indicate?