PIC Materials Testing & Asphalt Composition 2 — Questions and Answers
Question 1: What does the term 'air voids' refer to in a compacted asphalt mix?
- The total volume of aggregate particles
- The percentage of empty space not filled by asphalt binder or aggregate (Correct answer)
- The volume of binder absorbed by aggregate
- The space occupied by mineral filler
Correct answer: The percentage of empty space not filled by asphalt binder or aggregate
Air voids are the percentage of total mix volume that consists of small air spaces not filled by asphalt or aggregate.
Question 2: A Marshall stability test measures which property of an asphalt mix?
- Binder viscosity at high temperatures
- Resistance of the compacted specimen to deformation under load (Correct answer)
- Aggregate gradation compliance
- Moisture susceptibility of the mix
Correct answer: Resistance of the compacted specimen to deformation under load
The Marshall stability test measures the maximum load a compacted asphalt specimen can resist before deforming under a specified loading rate.
Question 3: Which sieve size is used as the maximum aggregate size designation for a 19 mm Superpave mix?
- 9.5 mm
- 12.5 mm
- 19.0 mm (Correct answer)
- 25.0 mm
Correct answer: 19.0 mm
The nominal maximum aggregate size for a 19 mm Superpave mix is 19.0 mm, meaning 100% of aggregate passes the next larger sieve.
Question 4: The dust-to-binder ratio in a Superpave mix is calculated by dividing the percent passing the No. 200 sieve by:
- The asphalt binder content by total mix weight
- The effective binder content by total mix weight (Correct answer)
- The aggregate surface area
- The total VMA of the mix
Correct answer: The effective binder content by total mix weight
The dust-to-binder ratio divides the percent of material passing the No. 200 sieve by the effective asphalt binder content expressed as a percentage of total mix mass.
Question 5: During field extraction testing of an asphalt core, what is the primary purpose of centrifuge extraction?
- To determine compressive strength of the core
- To separate the asphalt binder from the aggregate for content measurement (Correct answer)
- To measure the film thickness on aggregate particles
- To identify the specific gravity of the binder
Correct answer: To separate the asphalt binder from the aggregate for content measurement
Centrifuge extraction uses a solvent to separate and recover the asphalt binder from aggregate, allowing determination of binder content.
Question 6: What aggregate property does the Los Angeles Abrasion test evaluate?
- Particle shape and angularity
- Resistance to degradation by abrasion and impact (Correct answer)
- Absorption capacity of the aggregate
- Flat and elongated particle percentage
Correct answer: Resistance to degradation by abrasion and impact
The LA Abrasion test measures aggregate toughness and resistance to degradation caused by abrasion and impact using a rotating drum with steel charges.
Question 7: In the context of asphalt mix design, VMA stands for Voids in the Mineral Aggregate and represents:
- The total volume of air voids only
- The inter-granular void space between aggregate particles in a compacted mix (Correct answer)
- The volume of asphalt binder absorbed into aggregate
- The percentage of fine aggregate in the gradation
Correct answer: The inter-granular void space between aggregate particles in a compacted mix
VMA is the total volume of void space between aggregate particles in a compacted mix, including air voids and effective asphalt binder content.
PIC Materials Testing & Asphalt Composition 2
What does the term 'air voids' refer to in a compacted asphalt mix?