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This report describes a research project that provides Minnesota counties, and townships with information and procedures to make informed decisions on when it may be advantageous to upgrade and pave gravel roads. It also provides resources to assist county and township governments in explaining to the public why certain maintenance or construction techniques and policy decisions are made. The research involved three major efforts. The first is a historical cost analysis based on the spending history for low volume roads found in the annual reports of selected Minnesota counties. The effects of traffic volume and type of road surface on cost was included in the analysis. The second was the development of a method for estimating the cost of maintaining gravel roads, which is useful when requirements for labor, equipment and materials can be predicted. The third is the development of an economic analysis example that can serve as a starting point for analyses to aid in making specific decisions. Additional information was gleaned from numerous interviews with local road officials. Maintenance and upgrading activities considered included: maintenance grading, re-graveling, dust control/stabilization, reconstruction/re-grading, paving, and others. As part of this report, an analysis is developed that compares the cost of maintaining a gravel road with the cost of upgrading to a paved surface. This analysis can be modified to address local conditions. Such an analysis may be used as a tool to assist in making decisions about upgrading a gravel road to a paved surface.

This study documents relationships between intelligent compaction measurement values (IC-MVs) and various insitu point measurement techniques for monitoring compaction of non-granular and granular materials. Factors affecting correlations are discussed (e.g., soil type, moisture contents, stress level, etc.). Measurements from earth pressure cells document the relationship between in-ground stresses for rollers and various in-situ test methods. Comparisons were made between test roller rut depth measurements and IC-MVs and various point measurements as a quality assurance (QA) check for the subgrade pavement foundation layer. It was concluded that IC-MVs and in-situ point measurements can serve as reliable alternatives to test rolling. Site specific target values were calculated for IC-MVs, dynamic cone penetrometer (DCP), light weight deflectometer, (LWD), and shear strength. Measurement error and protocols for field testing were evaluated for LWDs. Laboratory compacted samples were used to assess an approach for determining LWD field target values. Future research is recommended to evaluate this approach for materials on a state-wide basis. Results from field studies were used to develop four IC specification options. Three specifications do not require on-site roller calibration. One specification option requires on-site calibration of IC-MVs and in-situ point measurements. This specification option has the advantages of quantifying risk, establishing a framework for a performance specification, providing information for incentive-based pay, and better linking as-built quality to long-term performance. An IC training/certification program, new IC field data analysis tools, and additional pilot projects will assist with greater implementation of these technologies.

The successful implementation of intelligent compaction technology into earthwork construction practice requires knowledge of the roller-integrated compaction measurements and their relationships with the engineering and index properties of soil that may be used for pavement design (e.g. California bearing ratio, elastic modulus, resilient modulus). These relationships were studied at three earthwork construction projects in Minnesota. In these field studies, intelligent compaction and in-situ test data were collected to demonstrate use of the various technologies, characterize the variation associated with each measurement system, and ultimately aid performance of regression analyses. For the pilot study at TH 64, a GIS database was created with roller data and parallel quality assurance data to demonstrate one method for managing large quantities of data. Spatial statistics were also determined using variogram modeling and discussed with regards to their potential for characterizing uniformity. A laboratory compaction study using different compaction methods (e.g. static, impact, gyratory, and vibratory) was conducted to show different moisture-density-compaction energy relationships for granular and cohesive soils. Resilient modulus test results showed that vibratory and impact compaction methods produce higher-modulus samples than static compaction. The findings from field studies of intelligent compaction systems provide the basis for developing QC/QA guidelines regarding effective and appropriate use of the technology. These recommendations, along with a brief summary of European specifications for continuous compaction control, are provided in the report.