University of Vermont Transportation Research Center

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Intelligent Compaction (IC) is considered to be an innovative technology intended to address some of the problems associated with conventional compaction methods of earthwork (e.g. stiffness-based measurements instead of density-based measurements). IC typically refers to an improved compaction process using rollers equipped with an integrated measurement system that consists of a global positioning system (GPS), accelerometers, onboard computer reporting system, and infrared thermometers IC determines the compacted material’s stiffness/modulus simultaneously while compacting based on measured frequency and amplitude of excitation. The overarching objective of this research was to investigate the suitability of IC technology for comparatively smaller-scale embankment, subgrade, and base material construction that are typical for Vermont. The specific objectives were to: perform a literature review of IC technology; assess the accuracy and reliability of IC measured values (e.g. stiffness); investigate the influence of relevant parameters (i.e. density, soil type, moisture content, etc.) on these measurements; investigate different options for quality control (QC) and quality assurance (QA) specifications for IC; and make specific recommendations to the Agency. The literature review suggests that: (i) IC stiffness measurements near the surface are less reliable compared to deeper measurements; (ii) correlations between IC measured stiffness and modulus of spottest measurements vary considerably in layer and layered soil structures; and (iii) for asphalt, IC measured stiffness correlates well with nuclear density gauge measurements, only when the asphalt mix is hot. In addition, the existing quality control (QC) and quality assurance (QA) specifications for implementing IC need further improvements. It is suggested that to better investigate the reliability of implementing IC for both earthwork construction and asphalt pavement in Vermont’s harsh winter conditions, it would be necessary to conduct field experiments. In addition, preparing a new set of QC/QA specifications is an important step toward implementation of IC in Vermont projects, which can be accomplished in collaboration with other states and as some local experience in IC is gained. Also, it is recommended to evaluate the correlation between IC stiffness measurements and in-situ stiffness measurements in different seasons in Vermont.