PIC Materials Testing & Asphalt Composition 3 — Questions and Answers
Question 1: The Performance Grade (PG) designation for an asphalt binder, such as PG 64-22, indicates:
- The viscosity at 60°C and penetration at 25°C
- The high-temperature reliability limit and low-temperature cracking resistance limit in °C (Correct answer)
- The softening point and ductility of the binder
- The mixing temperature and compaction temperature in °F
Correct answer: The high-temperature reliability limit and low-temperature cracking resistance limit in °C
In a PG grade like PG 64-22, 64°C is the maximum pavement temperature the binder resists rutting, and -22°C is the minimum temperature at which it resists thermal cracking.
Question 2: A Hamburg Wheel-Track test is used to evaluate an asphalt mix for:
- Tensile strength at cold temperatures
- Rutting resistance and moisture susceptibility under repeated loading (Correct answer)
- Fatigue cracking under cyclic flexural stress
- Aggregate stripping due to freeze-thaw cycles
Correct answer: Rutting resistance and moisture susceptibility under repeated loading
The Hamburg Wheel-Track test subjects a submerged asphalt specimen to repeated wheel passes to evaluate both rutting and stripping potential.
Question 3: What does the Tensile Strength Ratio (TSR) measure in an asphalt mix?
- The ratio of air voids to total voids in the mix
- The ratio of conditioned indirect tensile strength to unconditioned tensile strength (Correct answer)
- The ratio of binder content to aggregate surface area
- The ratio of stability to flow in a Marshall specimen
Correct answer: The ratio of conditioned indirect tensile strength to unconditioned tensile strength
TSR compares the indirect tensile strength of moisture-conditioned specimens to dry specimens, indicating the mix's resistance to moisture damage.
Question 4: Reclaimed Asphalt Pavement (RAP) incorporated into new HMA mixes primarily contributes:
- Only virgin aggregate without any binder benefit
- Aged asphalt binder and aggregate, reducing the demand for virgin materials (Correct answer)
- Increased air void content and better drainage
- Higher film thickness on virgin aggregate particles
Correct answer: Aged asphalt binder and aggregate, reducing the demand for virgin materials
RAP contains both aged asphalt binder and aggregate that can replace a portion of virgin materials, reducing cost and improving sustainability.
Question 5: The Superpave Gyratory Compactor (SGC) compacts specimens at a fixed angle of gyration of:
- 0.5 degrees
- 1.25 degrees (Correct answer)
- 2.0 degrees
- 3.5 degrees
Correct answer: 1.25 degrees
The SGC compacts specimens at a fixed internal angle of gyration of 1.25 degrees, simulating field compaction by kneading the material.
Question 6: When testing aggregate for flat and elongated particles, which ratio is most commonly used in Superpave specifications?
- 1:2
- 3:1
- 5:1 (Correct answer)
- 4:1
Correct answer: 5:1
Superpave specifications typically require that flat and elongated particles be limited using a 5:1 ratio of maximum to minimum particle dimensions.
Question 7: What AASHTO test method is used to determine the bulk specific gravity of compacted HMA specimens?
- AASHTO T 85
- AASHTO T 166 (Correct answer)
- AASHTO T 209
- AASHTO T 19
Correct answer: AASHTO T 166
AASHTO T 166 (Bulk Specific Gravity of Compacted Hot-Mix Asphalt) determines the bulk specific gravity of compacted mixtures using a water displacement method.
PIC Materials Testing & Asphalt Composition 3
The Performance Grade (PG) designation for an asphalt binder, such as PG 64-22, indicates: