HMA Design (Surface) CEE 320 Steve Muench 06/27/22 1 The surface course is the layer in contact with traffic loads and normally contains the highest quality materials. It provides characteristics such as friction, smoothness, noise control, rut and shoving resistance and drainage.
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HMA Design (Surface) CEE 320 Steve Muench 4/28/2015 1 The surface course is the layer in contact with traffic loads and normally contains the highest quality.
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HMA Design (Surface)
CEE 320Steve Muench
04/18/23 1
The surface course is the layer in contact with traffic loads and normally contains the highest quality materials. It provides characteristics such as friction, smoothness, noise control, rut and shoving resistance and drainage.
Surface HMA
This top structural layer of material is sometimes subdivided into two layers:
Wearing Course. This is the layer in direct contact with traffic loads. It is meant to take the brunt of traffic wear and can be removed and replaced as it becomes worn. A properly designed (and funded) preservation program should be able to identify pavement surface distress while it is still confined to the wearing course. This way, the wearing course can be rehabilitated before distress propagates into the underlying intermediate/binder course.
Intermediate/Binder Course. This layer provides the bulk of the HMA structure. Its chief purpose is to distribute load.
HMA Types
The three most common types of HMA pavement are:
Dense-graded HMA. Flexible pavement information in this Guide is generally concerned with dense-graded HMA. Dense-graded HMA is a versatile, all-around mix making it the most common and well-understood mix type in the U.S.
Stone matrix asphalt (SMA). SMA, although relatively new in the U.S., has been used in Europe as a material for years to support heavy traffic loads and resist studded tire wear. Also known as Gap Graded
Open-graded HMA. This includes both open-graded friction course (OGFC) and asphalt treated permeable materials. Open-graded mixes are typically used as wearing courses (OGFC) or underlying drainage layers because of the special advantages offered by their porosity.
Dense-Graded HMA
Stone Matrix Asphalt (SMA)
Open-Graded Mixes
0.45 Power Gradation
0.45 Power Gradation Curve Using 19.0-mm (0.75-inch) Maximum Aggregate Size
Calculations for a 0.45 Power Gradation Curve Using 19.0-mm (0.75-inch) Maximum Aggregate Size
0.45 Power Gradation Curve for Different Maximum Aggregate Sizes