CCIL Asphalt and Aggregate 3 — Questions and Answers
Question 1: What is the significance of the 'recovered asphalt' concept in pavement recycling?
- Fresh asphalt added to RAP to restore stiffness
- Asphalt binder extracted from RAP for testing and characterization (Correct answer)
- Asphalt heated and re-compacted without modification
- Asphalt binder blended with rubber crumb only
Correct answer: Asphalt binder extracted from RAP for testing and characterization
Recovered asphalt refers to the binder extracted from reclaimed asphalt pavement (RAP) through solvent extraction or ignition, allowing its properties to be characterized and factored into mix design.
Question 2: Which ASTM test method determines the resilient modulus of asphalt concrete?
- ASTM D4123 (Correct answer)
- ASTM D1559
- ASTM D2172
- ASTM D2041
Correct answer: ASTM D4123
ASTM D4123 covers indirect tension testing of cylindrical bituminous specimens to determine resilient modulus.
Question 3: In aggregate quality testing, what does the term 'flat and elongated' particle refer to according to ASTM D4791?
- Particles with a ratio of longest to shortest dimension exceeding 3:1 or 5:1 (Correct answer)
- Particles with smooth, rounded surfaces
- Particles passing the No. 200 sieve
- Particles with a specific gravity below 2.5
Correct answer: Particles with a ratio of longest to shortest dimension exceeding 3:1 or 5:1
ASTM D4791 defines flat and elongated particles as those where the ratio of maximum to minimum dimension exceeds a specified threshold, typically 3:1 or 5:1.
Question 4: What is the primary purpose of the Bending Beam Rheometer (BBR) test in asphalt characterization?
- Measure resistance to rutting at high temperatures
- Determine low-temperature stiffness and relaxation properties of asphalt binder (Correct answer)
- Assess aggregate stripping potential
- Measure dynamic shear modulus at intermediate temperatures
Correct answer: Determine low-temperature stiffness and relaxation properties of asphalt binder
The BBR (AASHTO T313) measures the creep stiffness and m-value of asphalt binder at low temperatures to predict thermal cracking performance.
Question 5: Which specification parameter controls rutting resistance in Superpave Performance Grade (PG) binder testing?
- BBR creep stiffness S(t) ≤ 300 MPa
- DSR G*/sinδ ≥ 1.0 kPa for original binder (Correct answer)
- RTFO mass loss ≤ 1.0%
- Absolute viscosity ≤ 3 Pa·s
Correct answer: DSR G*/sinδ ≥ 1.0 kPa for original binder
In Superpave PG grading, the DSR G*/sinδ ≥ 1.0 kPa for original binder (and ≥ 2.2 kPa after RTFO aging) ensures adequate rutting resistance at high pavement temperatures.
Question 6: What is the purpose of the sodium sulfate soundness test (ASTM C88) for aggregate?
- Evaluate aggregate resistance to freeze-thaw deterioration (Correct answer)
- Determine aggregate specific gravity
- Measure aggregate absorption capacity
- Assess aggregate alkali-silica reactivity
Correct answer: Evaluate aggregate resistance to freeze-thaw deterioration
The sodium sulfate soundness test simulates the disruptive force of ice crystal growth within aggregate pores to assess durability under freeze-thaw conditions.
Question 7: In asphalt mix production, what is the function of a drum mixer (drum plant) compared to a batch plant?
- Batch plants produce higher quality mixes than drum plants
- Drum plants continuously mix aggregate and asphalt in a rotating drum for higher production rates (Correct answer)
- Drum plants can only produce cold-mix asphalt
- Batch plants produce mix continuously without stopping
Correct answer: Drum plants continuously mix aggregate and asphalt in a rotating drum for higher production rates
Drum mix plants continuously dry, heat, and mix aggregate with asphalt binder in a rotating drum, allowing higher production rates compared to batch-by-batch processing in batch plants.
CCIL Asphalt and Aggregate 3
What is the significance of the 'recovered asphalt' concept in pavement recycling?