About the research
This report presents results and findings of the Phase II Iowa Department of Transportation Roller Integrated Compaction Monitoring (RICM) Technology Research and Implementation program. During this phase of the project, special provisions (SPs) were developed that required RICM technologies on three hot mix asphalt (HMA) overlay pilot projects in Iowa. The field results are presented for each project.
The bid item cost for implementing the RICM-HMA SPs on each project varied from 0.9% to 1.4% of total project cost. The SP on US30 Harrison County project required RICM roller coverage including temperature, pass count, and compaction measurements on one break down roller. The SP on US20 Ida County project required RICM roller coverage including temperature and pass count on one break down roller. The SP on IA9 Kossuth County project required roller pass count coverage for all compaction equipment. The SPs were successfully implemented on US30 and US20 projects and the information from the RICM rollers conveniently met the requirements of the SPs for roller coverage. The IA9 project encountered problems with roller data storage/export during construction leading to not meeting the coverage requirements of the project SP.
Testing was conducted on each project by the Iowa State University research team beyond the requirements of the project specifications to analyze asphalt density, RICM values, and asphalt surface temperature changes with pass count and time. Comparisons between RICM values and asphalt density/percent compaction yielded poor correlations, but relationship with falling weight deflectometer modulus values revealed good correlations. Influence of the foundation support conditions under the asphalt surface layer is a major contributor to characterizing correlations between RICM measurements and asphalt density measurements. Geostatistical analysis of pass coverage information revealed differences in pass coverage uniformity between projects. The key benefits of implementing RICM technology for HMA overly projects are documenting the pass coverage/uniformity and the compaction-time-surface temperature history. Future research should be conducted to evaluate this technology on full-depth HMA projects.