PIC Aggregate & Binder Specifications 2 — Questions and Answers
Question 1: Which AASHTO specification governs the performance grading (PG) system for asphalt binders used in HMA pavements?
- AASHTO M 320 (Correct answer)
- AASHTO M 156
- AASHTO T 315
- AASHTO M 208
Correct answer: AASHTO M 320
AASHTO M 320 establishes the performance-graded (PG) asphalt binder specification, including temperature-based grade designations.
Question 2: A PG 76-22 binder is designed to perform in high pavement temperatures up to:
- 76°C (Correct answer)
- 22°C
- 64°C
- 82°C
Correct answer: 76°C
In the PG grading system, the first number (76) represents the maximum pavement temperature (°C) at which the binder is designed to perform.
Question 3: Which test measures the low-temperature cracking resistance of an asphalt binder by evaluating its creep stiffness?
- Bending Beam Rheometer (BBR) (Correct answer)
- Dynamic Shear Rheometer (DSR)
- Rolling Thin Film Oven (RTFO)
- Pressure Aging Vessel (PAV)
Correct answer: Bending Beam Rheometer (BBR)
The Bending Beam Rheometer (BBR) measures the creep stiffness and m-value of asphalt binder at low temperatures to predict thermal cracking resistance.
Question 4: The Los Angeles (L.A.) Abrasion test evaluates aggregate resistance to:
- Degradation and wear (Correct answer)
- Moisture damage
- Thermal expansion
- Shape and angularity
Correct answer: Degradation and wear
The L.A. Abrasion test measures aggregate toughness and resistance to degradation through abrasion and impact using steel balls in a rotating drum.
Question 5: In Superpave mix design, the term 'restricted zone' historically referred to a region on the:
- Aggregate gradation chart where blends should avoid (Correct answer)
- DSR frequency sweep curve
- Asphalt binder viscosity chart
- Compaction curve for gyratory compactor
Correct answer: Aggregate gradation chart where blends should avoid
The Superpave restricted zone was a band on the 0.45 power gradation chart that aggregate blends were originally discouraged from passing through, though this requirement was later eliminated.
Question 6: Which aggregate property is measured by the sodium sulfate soundness test?
- Resistance to freeze-thaw deterioration (Correct answer)
- Particle shape and angularity
- Adhesion to asphalt binder
- Surface texture roughness
Correct answer: Resistance to freeze-thaw deterioration
The sodium sulfate (or magnesium sulfate) soundness test assesses aggregate durability by simulating the expansive forces of freezing water within aggregate pores.
Question 7: What does the term 'nominal maximum aggregate size' (NMAS) refer to in HMA specifications?
- One sieve size larger than the first sieve to retain more than 10% of aggregate (Correct answer)
- The sieve size retaining the most aggregate by weight
- The largest aggregate particle in the mix
- The sieve size passing 100% of the aggregate
Correct answer: One sieve size larger than the first sieve to retain more than 10% of aggregate
NMAS is defined as one sieve size larger than the first sieve that retains more than 10% of the aggregate, establishing the upper boundary of a mix's gradation.
PIC Aggregate & Binder Specifications 2
Which AASHTO specification governs the performance grading (PG) system for asphalt binders used in HMA pavements?