Evaluation of Automated Process Control Testing for Hot-Mix Asphalt Production

Numerous advances have been made in the hot-mix asphalt (HMA) industry over the past several decades. However, the basic practices for assuring the quality of hot mix asphalt during production have changed little during this period. Significant advancements may be possible in HMA quality and performance if automated measurement technologies are developed within the industry. Current processes for quality control of HMA place considerable risks on HMA producers and transportation agencies. This project was established to explore new ways of gathering rapid process control information with automated testing devices. The two primary goals of automated testing are to dramatically shrink the time lag for quality control information and to improve the reliability of the data. This report provides a summary of the first significant field test case for automating several basic elements of quality control testing during HMA production. Automated devices were installed on a HMA plant to determine gradations of the aggregates, moisture content of the aggregates, viscosity of the asphalt binder, asphalt content of the HMA, and discharge temperature of the mix. Although the information gathered with these automated devices only provides part of the overall picture for a QC operation at a plant, the preliminary feasibility of automated testing technologies can be made. The results of this pilot project show that automated testing equipment refinements need to continue, but there is a great deal of promise in the concept of automated process control testing.