About the research
Phase I Report:
The Iowa Department of Transportation Intelligent Compaction Research and Implementation was initiated in summer 2009. Three field demonstration projects were conducted in Iowa as part of Phase I of this research program to evaluate three different IC measurement technologies: (1) machine drive power (MDP) measurement technology on Caterpillar CP56 padfoot roller, (2) continuous compaction value (CCV) technology on Sakai SW880 dual vibratory smooth drum asphalt roller, and (3) compaction meter value (CMV) technology on Volvo SD116DX smooth drum vibratory roller. The main objectives of the project include the following:
- Evaluating the effectiveness of the IC measurement values (IC-MVs) in assessing the compaction quality of cohesive subgrade materials, granular base/subbase materials, and HMA materials,
- Developing project specific correlations between IC-MVs and various conventionally used in-situ point measurements in earthwork quality control (QC) and quality assurance (QA) practice and HMA construction,
- Evaluating the advantages of using the IC technology for production compaction operations,
- Obtaining data to evaluate future IC specifications, and
- Developing content for future educational and training materials for Iowa DOT and contractor personnel for effective implementation of the technology in to earthwork and HMA construction practice.
This research report presents results obtained from the three demonstration projects along with an overview of the different IC technologies and various QC/QA test methods. Statistical regression analysis was performed to evaluate correlations between IC-MVs and various in-situ test measurements (e.g., dry unit weight, moisture content, modulus, California bearing ratio, temperature (for HMA)). Comparatively, modulus was better correlated with IC-MVs compared to dry unit weight. Geostatistical analysis methods were used to assess “uniformity” of the spatially referenced IC measurements. Results from this study were used to develop special provision specifications as part of Phase II research program.
Phase II Report:
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.