Hoegh, Kyle

A performance monitoring and forensic study was conducted on several test sections with varying base and pavement characteristics. This report includes the performance data from the current phase, which was extended until pavement reconstruction, with the previously reported data, collected since original construction of the test sections. Each of the three original test sections were prepared with a different combination of base type and asphalt binder type. Three different crushed limestone base types were used in the construction: (Section 1) standard Class 5, (Section 2) permeable aggregate base (PAB), and (Section 3) Class 5 modified. Two different types of asphalt binders, PG 58-28 and PG 58-34, were incorporated to evaluate the effects of cold temperature cracking. All asphalt mixtures were designed according to MnDOT Specification 2350. In addition to the comparisons among sections, each road section was constructed, both with and without transverse sawn-and-sealed regularly spaced joints, to evaluate the relative performance for ride and cracking (both spacing and crack severity) of sawing and sealing (S&S) versus allowing thermal cracking to relieve tensile stress without sawing and sealing (non-S&S). Prior to reconstruction, the severity of cracking in Section 1 was significantly higher than in Sections 2 and 3, with no severe cracking observed in Section 3. This study confirmed previous research efforts on this project, indicating that the combination of PG58-34 binder with Class 5 modified base material (Section 3) and PAB base (Section 2) performed well as compared to the control section. Seasonal trends of reduced stiffness during spring thaw followed by rapid recovery were also observed in the FWD analysis.

This paper presents the results of a blind test evaluation of various nondestructive testing techniques including well established methods such as chain dragging, rod sounding, and GPR as compared to an emerging ultrasonic array technology in determining the extent of the concrete joint deterioration. Nondestructive testing at two concrete pavement joints at MnROAD was performed and the results were independently evaluated and submitted to MnDOT. Significant discrepancies in subsurface deterioration assessments were observed among these techniques. Forensic evaluation (trenching and coring) were utilized to resolve the discrepancies in test results. It was concluded that the ultrasound array analysis was the only method able to accurately determine the horizontal extent of the deterioration otherwise undetected by the other available nondestructive evaluation methods. Additionally, ultrasonic tomography analysis was able to determine the depth of the deterioration. This makes this emerging technology an attractive alternative to traditional NDT methods for concrete pavement joint assessment. Paper submitted for the Transportation Research Board 92nd Annual Meeting, 13-17 January 2013.

Benefits from a potential significant correlation between distresses and slab thickness can be broadly applied in all stages of highway development from design and construction to maintenance decisions. In order to comprehensive explore this possibility, thickness data and existing distresses were related for three highway projects in Minnesota. Thickness was obtained through non-destructive ultrasonic testing, while distresses were recorded for the same location with a distress image software. Significant thickness variation was observed in both longitudinal and transverse directions. The combined results of thickness, shear wave velocity and distresses analysis revealed that an increase in shear wave velocity was coincident with a less damaged pavement area within a section. An in-depth statistical analysis confirmed this observation showing that shear surface velocity variation was better correlated with overall pavement performance than thickness variation. Differences in cracking behavior within a section were traced back to changes in construction and design practices, showing the potential of using shear velocity analysis for pavement maintenance. A survey and analysis procedure for shear wave velocity testing of concrete pavements is proposed.

The current empirical methods for determining traffic-opening criteria can be overly conservative causing unnecessary construction delays and user costs. The research described here recommends innovative mechanisticbased procedures for monitoring concrete early age development and evaluating the effect of early traffic opening on long-term damage accumulation. The procedure utilizes recent developments in nondestructive testing to optimize traffic opening timing without jeopardizing pavement longevity. These tasks were achieved via extensive field and laboratory experiments allowing for the analysis of variables such as curing condition and loading type with respect to the effect of early loading of concrete. The results of these efforts culminated in the development of a program that analyzes the effect of design and opening time decisions on pavement damage. The deliverable can be utilized by transportation agencies to make more informed decisions.

The recently introduced Mechanistic-Empirical Pavement Design Guide (MEPDG) and related software provide capabilities for the analysis and performance prediction of different types of flexible and rigid pavements. An important aspect of this process is the evaluation of the performance prediction models and sensitivity of the predicted distresses to various input parameters for local conditions and, if necessary, re-calibration of the performance prediction models. To achieve these objectives, the Minnesota Department of Transportation (MnDOT) and the Local Road Research Board (LRRB) initiated a study "Implementation of the MEPDG for New and Rehabilitated Pavement Structures for Design of Concrete and Asphalt Pavements in Minnesota." This report presents the results of the evaluation of default inputs, identification of deficiencies in the software, sensitivity analysis, and comparison of results to the expected limits for typical Minnesota site conditions, a wide range of pavement design features (e.g. layer thickness, material properties, etc), and the effects of different parameters on predicted pavement distresses. Since the sensitivity analysis was conducted over a span of several years and the MEPDG software underwent significant modifications, especially for flexible pavements, various versions of the MEPDG software were run. Performance prediction models of the latest version of the MEPDG 1.003 were evaluated and modified or recalibrated to reduce bias and error in performance prediction for Minnesota conditions.