This section contains a list of frequently asked questions that WAPA and WAPA members encounter.  Many of the question answers will take you directly to the WAPA Asphalt Pavement Guide for the answer (it will open in a separate window and jump to the appropriate section).

General

• How do I find a WAPA member paving contractor in my area?

• I want to build an asphalt driveway.  Where can I find information on hot mix asphalt driveways?

• Where can I find more information like this on hot mix asphalt (HMA) pavements?

• What is hot mix asphalt (HMA)?

• What is hot mix asphalt's environmental record? (This link takes you to beyondRoads.com)

• Is there a difference between tar and asphalt?

• What is a pavement's purpose?

• How much do we use roads in the U.S.?

• Do you have any pavement design and construction guidance?

• There is something wrong with my pavement.  What is it and how do I fix it?

Design Catalog

• How thick should I make my pavement?
• What are the basic structural elements in a pavement?
• What is a Perpetual Pavement?

Pavement Types

• What types of pavement are there?
• Are there different kinds of hot mix asphalt?
• What is Superpave?
• What is Stone Matrix Asphalt (SMA)?
• What is asphalt treated base (ATB)?
• What is RAP and how is it used?
• What types of standard HMA mixes are used in Washington State (e.g., Class A, Class G, etc.)?
• What is a Modified Class B mix?

Materials

• What is the difference between maximum aggregate size and nominal maximum aggregate size?
• What is the PG asphalt binder grading system?
• What is an asphalt binder modifier?

Design Factors

• What is the difference between a CBR, R-Value and resilient modulus and how do I correlate them to one another?
• What is an equivalent single axle load (ESAL)?
• What is frost heave and should I worry about it?

Mix Design

• What is a job mix formula (JMF)?
• What are the differences between the Hveem, Marshall and Superpave methods?

Structural Design

• What different structural design methods are there besides design catalogs?

Construction

• How should I prepare the surface over which I plan to place a new pavement or overlay?
• What is "Rice density"?
• Why are density measurements given as a percentage?
• Why are density and compaction so important?

Pavement Evaluation

• What is IRI?
• How are pavements evaluated?
• What is a life cycle cost analysis and are there any tools to help me perform one on a proposed pavement?

Maintenance & Rehabilitation

• What is a bituminous surface treatment, or chip seal?
• Are all overlays used to increase the structural capacity of a pavement?