University of Vermont Transportation Research Center

Document Type

Report

Publication Date

12-27-2019

Abstract

Compaction is one of the most important operations in pavement construction. Poor compaction of different pavement layers (i.e. subgrade, sub-base, base, and wearing course) can lead to various types of deterioration/failure, which consequently increases the cost of maintenance and rehabilitation. Therefore, it is crucial to control the compaction quality at different stages of road construction. Since the density-based Quality Control (QC) and Quality Assurance (QA) methods relying on spot-test measurements and retrieved-core testing can only cover less than 1% of the compacted area, it is difficult to ensure the uniformity and consistency of the compaction process. As a result, it is highly desired to transition from the current point-wise to a system-wide inspection practice. 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). The main objective of this project was to evaluate the performance of IC technology in the state of Vermont. At the initial stage of the project, the IC data from Bethel-Stockbridge project were analyzed to gain a better insight into IC performance. Then, a reclaimed asphalt pavement project (Route 117) was selected for field testing and data collection. During the first construction season, the field test plan and data analysis were focused on understanding the IC roller measurements (i.e. ICMVs) and their association with the point-wise measurements (Dynamic Cone Penetration, Nuclear Gauge Density, Pavement Quality Indicator). Then, during the second construction season, the field test plan was focused on evaluating the consistency of compaction operation using the IC roller. In addition, feasibility of using target ICMV, optimum number of passes and roller temperature data as QC tool were investigated. The results from field tests indicated a very weak correlation between the ICMVs and point-wise density measurements. Changing the underlying material and using inconsistent roller parameters were identified as the potential causes of this poor correlation. However, calibration of the roller parameters at the initial stage of the second construction season testing improved the correlations between ICMV and spot density measurements. Target ICMV and optimum number of passes determined at this stage were successfully used as QC tool. In addition, geo-spatial analysis indicated that using IC roller live monitoring system can potentially improve the consistency and uniformity of the compaction process. Finally, the temperature data recorded by IC roller were found to be reliable for utilization as a QC tool in the course of laying the HMA layer.

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