Composite Layering System

Layers of a System 3 application

ARAM can be used as a wearing surface on open highways and as a cape seal in residential areas (ARAM + Type II slurry). It also has a substantial history as a component in composite layering systems. This can be thought of as layers of a sandwich, where the ARAM is one of the layers placed between the existing surface and the top hot mix asphalt overlay, preventing water from penetrating into the subgrade and mitigating the hot mix asphalt from reflective cracking.

Composite layering systems are often alternatives to reconstruction, providing 12 to 15 years (or more) of maintenance-free performance at a fraction of the cost of other conventional strategies. Caltrans utilizes ARAM composite layering systems on highways, such as Interstate 5 near Valencia. Cities and counties apply millions of square yards of ARAM composite layering systems throughout California annually. Having ARAM as an interlayer allows the final hot mix asphalt overlay to be much thinner than if only hot mix asphalt was used because ARAM has an established one-half thickness equivalency as set forth in Caltrans' design guidelines. This provides cities, counties and other agencies significant savings by using substantially less material without sacrificing performance.

Final overlay surfacing of a System 3

There are two ways to utilize ARAM composite layering systems, known as System 3 and System 4 applications. Streets that are badly deteriorated and need a leveling course to adjust the surface irregularities will require a System 3 application, which has a leveling course, an ARAM interlayer and a final Asphalt-Rubber Hot Mix (ARHM) overlay. Streets with less distress that still require composite layering can use a System 4 application, which has an ARAM interlayer applied directly to the existing surface, followed by either an ARHM or a conventional hot mix asphalt overlay.

Composite layering can also be used with staged construction, where ARAM can act as the final wearing surface for several years until a final overlay is placed. This allows agencies to stretch their budgets over time, and the finished composite layering system will extend the life of the street for many more years. ARAM is the only product of its kind to have a substantial composite layering history in California.

To find out more information about ARAM, call the WPMA at (213) 683-1300 or e-mail

System 3 application cross section

P.O. Box 227206
Los Angeles, CA 90022
(213) 683-1300
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