PIC PIC Mix Design & Specification Compliance 1 — Questions and Answers
Question 1: In Superpave mix design, the performance grade (PG) of an asphalt binder is primarily determined by:
- The aggregate gradation and nominal maximum aggregate size
- The high and low pavement design temperatures at the project location (Correct answer)
- The target air void content and voids in the mineral aggregate
- The traffic loading expressed in Equivalent Single Axle Loads (ESALs)
Correct answer: The high and low pavement design temperatures at the project location
Superpave PG binder grading is based on the high and low pavement design temperatures at the project site, ensuring the binder performs adequately across the climate range.
Question 2: What does VMA stand for in hot-mix asphalt mix design?
- Variable Mix Acceptance
- Voids in the Mineral Aggregate (Correct answer)
- Verified Mix Analysis
- Viscosity of Modified Asphalt
Correct answer: Voids in the Mineral Aggregate
VMA (Voids in the Mineral Aggregate) is the total volume of inter-granular void space in a compacted mix, including air voids and effective asphalt binder content.
Question 3: A job mix formula (JMF) specifies the target gradation and binder content for an HMA mix. On a project, inspectors must verify that production mix properties are within:
- Exactly the JMF values with no deviation allowed
- The allowable tolerances established in the project specifications (Correct answer)
- 5% of the design values regardless of specification requirements
- Values approved by the contractor's quality control technician
Correct answer: The allowable tolerances established in the project specifications
Production mix properties must fall within the specification tolerances established around the JMF targets; deviations outside these limits require corrective action.
Question 4: The Nominal Maximum Aggregate Size (NMAS) of a Superpave mix is defined as:
- The sieve size that retains 100% of the aggregate
- One sieve size larger than the first sieve to retain more than 10% of the aggregate (Correct answer)
- The largest aggregate size used in the mix design
- The sieve size that passes 50% of the total aggregate blend
Correct answer: One sieve size larger than the first sieve to retain more than 10% of the aggregate
NMAS in Superpave is one standard sieve size larger than the first sieve that retains more than 10% of the combined aggregate blend.
Question 5: Which mix design method was widely used before Superpave became the FHWA standard and relies on stability and flow measurements from a standardized hammer-compacted specimen?
- Hveem Mix Design
- Marshall Mix Design (Correct answer)
- Gyratory Compaction Method
- SHRP Volumetric Design
Correct answer: Marshall Mix Design
The Marshall Mix Design method, which measures stability and flow of hammer-compacted specimens, was the dominant HMA design procedure before Superpave.
Question 6: Target air void content for a Superpave design mix at Ndesign gyrations is:
- 2%
- 4% (Correct answer)
- 6%
- 8%
Correct answer: 4%
Superpave mix design targets 4% air voids at the design number of gyrations (Ndesign), balancing durability and resistance to rutting.
PIC PIC Mix Design & Specification Compliance 1
In Superpave mix design, the performance grade (PG) of an asphalt binder is primarily determined by: