Using Imaging Technology to Improve the Laboratory and Field Compaction of HMA (0-5261-S)

This project summary report summarizes the research performed in Texas Department of Transportation (TxDOT) Project 0-5261. Insufficient compaction of asphalt mixtures leads to poor asphalt pavement performance, even if all desirable mixture design characteristics are met. This project evaluated the effect of changes in field compaction patterns on degree of compaction and uniformity of air void distribution in asphalt pavements. The research team developed a method to relate field compaction to laboratory compaction in order to predict asphalt mixture compactability based on laboratory measurements. Researchers compacted different types of hot mix asphalt (HMA) in a number of field projects and obtained cores from different locations of these projects. The effect of different levels of compaction on the performance of asphalt mixtures was studied, and an experimental laboratory procedure was developed to measure the moisture diffusion coefficients of HMA. Using methods from this project, the pavement designer can improve a mixture by selecting appropriate materials and mixture type and achieving the desired air voids in the field. Uniform air voids across the mat cannot be achieved by applying a uniform number of passes because the efficiency of compaction of a roller is not uniform across its width. A compaction roller equipped with a geographic information system (GIS) and a simple software program can be used to monitor the Compaction Index (CI) across the mat and adjust the compaction process for a uniform CI and a uniform percent air voids across the mat.