Procedure for Determining Mixing and Compaction Temperatures of Asphalt Binders in Hot Mix Asphalt
National Center for Asphalt Technology-Auburn University
Randy C. West
The project final report is available as NCHRP Report 648.
The Asphalt Institute (AI) procedure for determining mixing and compaction temperatures of asphalt binders was developed for the standard penetration- and viscosity-graded materials predominantly used in the United States until the 1990s. Since that time, the use of modified binders in hot mix asphalt (HMA) paving has increased significantly. This is particularly true for HMA used on high-volume traffic routes. The AI procedure often requires heating of modified binders to unrealistically high temperatures at which degradation of the asphalt binder can occur. To overcome this problem, highway agencies usually rely on the suppliers of modifiers to recommend mixing and compaction temperatures, and this has produced mixed results.
The objective of this study was to identify or develop a simple, rapid, and accurate laboratory procedure for determining the mixing and compaction temperatures of asphalt binder. The procedure would be (1) suitable for routine agency use, (2) applicable to both unmodified and modified binders and (3) based on testing of asphalt binders, HMA, or both.