Mix Design
Asphalt Mix Design
Superpave Mix Design
This method was developed as part of the Strategic Highway Research Program (SHRP) in the 1990s. It’s currently the standard mix design method in North America which considers traffic loading and environmental conditions. Superpave uses a gyratory compactor which simulates the compaction that the mix will experience during construction and under traffic.
Superpave mix design was initiated to construct more durable, longer-lasting asphalt pavements. These asphalt pavements can cope with increasing traffic volumes, axle loads and varying environments.
Superpave relies on volumetric properties of the asphalt mix. Performance-graded (PG) binders that account for temperature and aging conditions were introduced when Superpave was implemented.
Marshall Mix Design
Prior to Superpave, the Marshall mix design method was used. Although it is still used today in some states, it is most commonly used for fuel resistant airfield pavements. This procedure was developed in the 1940s, named after Bruce Marshall of the US Army Corps of Engineers. This method was developed as a means to identify the appropriate amount of asphalt needed in the mix and uses a Marshall Hammer for sample creation.
The Marshall method seeks to select the asphalt binder content at a desired density that satisfies minimum stability and range of flow values (Marshall Stability and Flow).
Federal Aviation Administration (FAA) Mix Design
FAA mix designs follow the specification requirements provided by the FAA for the design of asphalt mixtures used for airfields. The guidelines follow the P-400 specifications (P-401, P-403 and P-404). These mix designs require a high level of precision and quality control due to the unique load and safety requirements of airfields. Contractors must be familiar with these material and construction specifications before bidding on FAA projects, and the experts at ATS can help!
Balanced Mix Design (BMD)
Some states have recently implemented Balanced Mix Design. While Superpave designs have virtually eliminated rutting issues, BMD helps minimize cracking while preventing rutting. BMD considers mix aging, traffic, climate and the location within the pavement structure.
Balanced Mix Design evaluates the properties of the recovered binder from RAP to determine the PG grade of the virgin asphalt and/or modifiers used. The goal is to create a mix that offers a balance between resistance to rutting and cracking.
Pavement Preservation Mix Design
Pavement preservation is applying the right treatment to the right pavement at the right time. Pavement preservation mix designs are designed to maintain and extend the life of the existing pavement, minimize deterioration, enhance performance, improve safety and meet motorists’ expectations. Some common pavement preservation treatments are:
Other Asphalt Mix Designs
The asphalt mix designers at ATS are available to create designs using the following design methodologies:
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