PIC PIC Mix Design & Specification Compliance 2 — Questions and Answers
Question 1: Reclaimed Asphalt Pavement (RAP) is used in HMA mixes primarily to:
- Increase the binder content above specification requirements
- Reduce material costs and conserve virgin aggregate and binder (Correct answer)
- Improve the high-temperature performance grade of the mix
- Replace the need for a tack coat between lifts
Correct answer: Reduce material costs and conserve virgin aggregate and binder
RAP recycles aged pavement material, reducing the need for virgin aggregate and binder, which lowers material costs and conserves resources.
Question 2: When a paving inspector reviews plant tickets, the binder content is reported as percent by:
- Volume of the total mix
- Total weight of the mix (percent by total mass) (Correct answer)
- Weight of aggregate only
- Volume of aggregate in the mix
Correct answer: Total weight of the mix (percent by total mass)
Asphalt binder content is reported as a percentage of the total weight of the mix (percent by total mass), not just the aggregate weight.
Question 3: Voids Filled with Asphalt (VFA) is calculated as:
- Air voids divided by VMA times 100
- VMA minus air voids, divided by VMA, times 100 (Correct answer)
- Binder content divided by total mix volume times 100
- Aggregate volume divided by total mix volume times 100
Correct answer: VMA minus air voids, divided by VMA, times 100
VFA is the percentage of VMA filled with effective asphalt binder, calculated as (VMA − air voids) / VMA × 100.
Question 4: A polymer-modified asphalt binder (PMA) is typically specified on projects with:
- Low traffic volumes and thin pavement sections
- High traffic volumes, heavy loads, or extreme temperatures requiring enhanced performance (Correct answer)
- Low-temperature applications in northern climates only
- Thin overlays on low-volume rural roads
Correct answer: High traffic volumes, heavy loads, or extreme temperatures requiring enhanced performance
PMA is used where enhanced rutting resistance, improved fatigue life, or better low-temperature cracking resistance is required, such as high-traffic or extreme climate locations.
Question 5: During HMA production, if the aggregate gradation consistently plots above the maximum density line (MDL) on a 0.45-power gradation chart, the mix is considered:
- Too coarse, lacking fine aggregate filler
- Too fine, with an excess of fines relative to coarse aggregate (Correct answer)
- Correctly balanced for optimum compaction
- Outside specification limits regardless of other volumetric properties
Correct answer: Too fine, with an excess of fines relative to coarse aggregate
Gradation plotting above the MDL on a 0.45-power chart indicates excess fine material in the aggregate blend, which can increase binder demand and reduce stability.
Question 6: The moisture susceptibility of an HMA mix is most commonly evaluated using which test?
- Lottman Test (AASHTO T 283 — Tensile Strength Ratio) (Correct answer)
- Hamburg Wheel Tracking Test
- SHRP Asphalt Binder Rotational Viscosity Test
- Los Angeles Abrasion Test
Correct answer: Lottman Test (AASHTO T 283 — Tensile Strength Ratio)
AASHTO T 283 (commonly called the Lottman test) evaluates moisture susceptibility by comparing the tensile strength of conditioned versus unconditioned specimens as the Tensile Strength Ratio (TSR).
PIC PIC Mix Design & Specification Compliance 2
Reclaimed Asphalt Pavement (RAP) is used in HMA mixes primarily to: