Preliminary Field Investigation of Intelligent Compaction of Hot-mix Asphalt

About the report:

Attention is being directed toward intelligent compaction (IC) of pavement layers, which uses rollers especially manufactured to determine the degree of compaction and regulate the compactive effort required to produce a pavement layer with the optimum density. An IC roller should also have the capability to record a mix characteristic that can be correlated with the density of the final product. In this study, a small field investigation was conducted to determine if the stiffness measured by a particular IC roller correlated with the density of the thin surface layer of asphalt being compacted, thereby leading to a possible future end-result acceptance tool. The roller patterns were also used to determine whether the IC roller was more efficient than a conventional vibratory roller, i.e., whether fewer roller passes were required than with a conventional roller. The following were concluded from the results of the study: 1. The IC roller was not more efficient than the conventional vibratory roller. The IC roller may not have been able to capitalize on its "intelligent" features to provide more compactive effort when needed because of the thinness and fineness of the mat being placed in this study. A thicker, coarser mat such as that obtained with stone matrix asphalt might have produced different results. 2. The correlation between IC stiffness measurements and pavement density was poor. Three possible reasons for the lack of correlation were the effect of the decreasing temperature of the mat on stiffness, the variation in stiffness of the underlying layers, and the use of an incorrect roller "hammer" setting. 3. As noted in the previous conclusions, proper project selection and conduct of IC experiments are important. A new construction project would eliminate the possibility of the underlying structure influencing compaction or stiffness readings, and the presence of knowledgeable equipment personnel on the project would ensure proper operation of the equipment. 4. The IC method of compaction is not ready for use in asphalt construction at this time. 5. Although the results of this project were not encouraging with regard to the potential use of IC rollers in asphalt construction, they should not discourage additional studies and should aid in the planning of an imminent national pooled fund study.

Authors