Material Types

Our objective here is to give you a brief overview of the different types of Hot-Mix Asphalt (HMA) that are available. After this section you will have the option to examine our Material Thickness Guidelines section, which will help you to finalize your design. Please keep in mind, that these are simply general guidelines. Your best course of action is to contact us for a free estimate and consultation from one of our project managers.

For simplicity, we will only include those material types normally used in the paving of driveways and parking lots. Those materials can be divided into two main categories – wearing courses and base courses.

Wearing Course – The upper (surface) layer in the pavement system. It usually consists of a smaller maximum aggregate size (9.5 mm or 3/8”). It is designed to provide a smooth riding surface and to seal the surface from water penetration. A wearing course is often used by itself for driveways and parking lots, provided the stone subbase is adequate. The two most common wearing courses are 9.5 mm and ID-2. There is also a heavy duty wearing course called ID-3 which contains a slightly larger maximum aggregate size (19 mm or 3/4”). ID-3 is often used in place of ID-2 when additional strength is needed (i.e. private lanes, farms, parking lots, etc.).

Base Course – The layer in the pavement system immediately below the wearing course (or the binder course, if used). It usually consists of a larger maximum aggregate size (25 mm or 1”), creating a strong foundation for the wearing course. A base course cannot be used by itself, as it will begin to deteriorate if the wearing course is not applied within a few years. The two most common base courses are 25 mm and Bituminous Concrete Base Course (BCBC).

Furthermore, each of those categories can be divided into two subcategories – SUPERPAVE mix designs and Marshall mix designs. The difference between these two subcategories is not noticeable to the average consumer. Unless you are a materials engineer, the difference between the two is likely of little importance to you. The following information is supplied simply as a reference.

SUPERPAVE® – Superior Performing Asphalt Pavement. A method of mix design, developed under the Strategic Highway Research Program (SHRP), whereby samples are compacted with a SUPERPAVE gyratory compactor and tested for volumetric properties. The SUPERPAVE system was developed to give highway engineers and contractors the tools they need to design asphalt pavements that will perform better under extremes of temperature and heavy traffic loads. The 9.5 mm (wearing course) and 25 mm (base course) materials referenced above are SUPERPAVE mixes.

Marshall - A method of mix design developed by the U.S. Army Corps of Engineers (USACE) and adapted by the Asphalt Institute, for the design of mixes for highway pavements in the United States and abroad, using impact compaction. The ID-2 (wearing course), ID-3 (heavy duty wearing course) and BCBC (base course) materials listed above are Marshall mixes.

In summary, here is a table of the various materials that may apply to your project:

We are sometimes asked which is better – SUPERPAVE or Marshall? There really is no right or wrong answer. Marshall materials have been in use on our highways, parking lots and driveways for over 50 years. SUPERPAVE materials are rather new, having only been used over the last decade or so. With the amount of testing that each mix has undergone, you can be assured that either type of mix will easily meet your needs.

Our next section, Material Thickness Guidelines, will help you to finalize your design.