Evaluation of intelligent compaction technology for densification of roadway subgrades and structural layers

Abstract

The overall goal of WHRP Study #0092-08-07 was to collect information and data on the use of intelligent compaction (IC) technology to allow the Wisconsin DOT to make an informed decision on any useful application of this technology. Three objectives were identified to meet the overall goal of the study: (1) identify the advantages and limitations of the IC technology; (2) determine the material types and conditions that might cause inaccurate decisions or output from the IC roller (e.g., the accuracy of the outputs regarding layer stiffness), and (3) provide recommendations to the Wisconsin DOT on the use and implementation of IC technology for pavement construction. Field demonstration projects were planned and executed to collect data and information related to the use of IC rollers in Wisconsin. The demonstration projects confirmed that IC for soils is more advanced than for hot mix asphalt (HMA) layers. Level 2 and Level 3 soil IC rollers can be used almost immediately in Wisconsin. Unfortunately, there are many more issues or unanswered questions for compacting HMA layers than for unbound layers. The two areas where IC rollers can have immediate positive benefits, especially for unbound materials, are: (1) as a testing device to continually map the stiffness of an area prior to placing both unbound and HMA materials to identify areas with weak supporting layers and, after the layer has been compacted, and (2) to develop stiffness-growth relationships to determine the rolling pattern and number of passes to achieve a specific stiffness level. The key technical issues include lift thickness, bridging localized construction defects, and the fact that the IC roller output is a composite value influenced by the supporting layers. Additional pilot projects are recommended to increase contractor and agency personnel's confidence in using this technology.