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The Minnesota Department of Transportation (Mn/DOT) has selected a 316L stainless steel schedule 40 pipe as a new dowel bar to be used as a bid alternative for its high performance Portland Cement Concrete (PCC) pavements. Although this dowel bar should provide sufficient shear transfer capacity and low concrete bearing stresses, there was a concern that lack of a solid core may not provide sufficient resistance of the cross-section to distortion under a heavy axle loading. In this study, long-term performance of the 316L stainless steel schedule 40 pipe was investigated by subjecting a doweled joint to accelerated repeated loads through the use of the Minnesota Accelerated Loading Facility (Minne-ALF-2). Assessment of the new dowel bar performance was performed based on comparison with the standard 1.5 inch diameter epoxy -coated round steel dowel. The following tasks were accomplished: redesign, assembly and calibration of new version of Minne-ALF, development of experimental design matrix, conduct of accelerated full-scale testing, and post-testing evaluation. The results from the MinneALF-2 tests illustrated that while the LTE for the stainless steel dowel tubes was lower than the LTE for the epoxy-coated dowels, the stainless steel tubes are capable of providing over 70% LTE in the long-term when installed in concrete pavement joints. The ability to withstand deformation and corrosion while providing sufficient long-term performance suggests that the stainless steel tube dowel is an attractive alternative to the solid epoxy-coated dowel for use in long-life pavements.

The report describes the construction and design of composite pavements as a viable design strategy to use an asphalt concrete (AC) wearing course as the insulating material and a Portland cement concrete (PCC) structural layer as the load-carrying material. These pavements are intended for areas with heavy trucks and problem soils to increase the service life and minimize maintenance. The project focused specifically on thermally insulated concrete pavements (TICPs) (that is, composite thin AC overlays of new or structurally sound existing PCC pavements) and developed design and construction guidelines for TICPs. Specific research objectives include determining behavior of the layers of the TICP system, understanding life-cycle costs and the feasibility of TICPs, and incorporating the results into design and construction guidelines. Both construction and design guidelines are considered in light of the construction and performance of TICP test sections at the Minnesota Road Research project (MnROAD).

The project "Simplified Design Table for Minnesota Concrete Pavements" led to the creation of MnPCC-ME, a standalone 32-bit Windows executable program to replace the preexisting RigidPave. Whereas RigidPave was based upon the outdated AASHTO 1993 design procedure for rigid pavements, MnPCC-ME is based on MEPDG version 1.1, a mechanistic-empirical design procedure that accounts for the effects of traffic loading and environment. Furthermore, MnPCC-ME was localized for Minnesota pavements through: 1) the use of local climate data and weigh-in-motion traffic data; 2) the incorporation of previously conducted calibrations of the MEPDG for Minnesota pavements; and 3) the inclusion of advanced analysis features included in MnPCC-ME's flexible design counterpart, MnPAVE. The development and source code of MnPCC-ME is detailed in this final report.

Eighteen chip-sealed roadways in eight cities and counties in Minnesota were evaluated both in the field (for condition surveys and density tests) and in the laboratory (for permeability; stripping; tensile-strength ratio; asphalt film thickness; and mix properties) to evaluate factors associated with stripping in asphalt pavements under chip-seal treatments. Analysis of the test data did not support an earlier MnDOT finding that high air voids were a cause of stripping under chip seals. For those locations that did exhibit stripping; the test data did not support a direct relationship between asphalt pavement density and stripping. In addition; the research did not determine a direct relationship between incidence of stripping and site/supplier data (e.g.; bituminous mixture; contractor; geographic location; or year of construction). This observation agreed with observations made by Minnesota city/county engineers. An additional outcome of the research is the large amount of testing data developed; which is documented fully in appendices to the final report.

This report documents the development of a procedure to determine the structural adequacy and need of seasonal axle load restrictions for Minnesota low-volume roads. This procedure has been implemented into a new program, TONN2010. Since it is anticipated that the results of this study will be widely used by Mn/DOT, city, and county engineers, as well as consulting engineers involved in analysis of the falling weight deflectometer (FWD) data collected by the transportation agencies, an emphasis was made on development of a simple, easy to implement procedure. To simplify the procedure's implementation, the number of inputs was minimized. TONN2010 utilizes pavement layer thicknesses, FWD deflection basins, air temperature of the previous day, pavement surface temperature at the time of testing, pavement location, and anticipated traffic. All the inputs required by TONN2010 can be easily obtained by the user. Using these inputs, TONN2010 proceeds to 1) backcalculate layer moduli using the backcalculation procedure developed in this study, 2) adjust the backcalculated moduli using MnPAVE temperature and seasonal adjustment factors, and 3) estimate pavement axle load capacity by mechanistic-empirical analysis. In addition to detailing TONN2010, the report further describes selection of the damage models, development of the backcalculation design procedure, determination of the critical structural responses, development of new structural rating indexes, and finally the calibration and validation of the proposed procedure.

The Minnesota Department of Transportation (Mn/DOT) began construction on the Minnesota Road Research Project (MnROAD) in 1991 and opened the full-scale pavement research facility to live traffic in 1994. Since the time of its construction, MnROAD, the first major test track since the AASHO Road Test of the 1950s and 1960s, has learned many lessons in pavement testing and pavement engineering on behalf of the greater pavement community. Researchers at the University of Minnesota reviewed these lessons from the first phase of MnROAD (the facility's first ten years of operation) for a project titled MnROAD Lessons Learned. The Lessons Learned project involved over fifty interviews, three hundred published and unpublished reports, papers, and briefs, and an online survey of pavement professionals. This paper, based on the Lessons Learned project, presents a sample of the lasting benefits of MnROAD at the local, state, and national levels. Furthermore, the paper provides extensive references for these benefits in hopes of increasing awareness of this pavement test facility's under-publicized contributions to pavement engineering. This paper was submitted for the Transportation Research Board 2008 Annual Meeting.

The Minnesota Department of Transportation (MnDOT) began construction on the Minnesota Road Research Project (MnROAD) in 1991 and opened the full-scale pavement research facility to live traffic in 1994. Since the time of its construction, MnROAD, the first major test track since the AASHO Road Test of the 1950s and 1960s, has learned a number of lessons on behalf of the greater pavement community. As part of completing the first phase of MnROAD (its first ten years of operation), researchers at the University of Minnesota reviewed the many products of MnROAD's first phase. The Lessons Learned project involved over fifty interviews, three hundred published and unpublished reports, papers, and briefs, and an online survey of pavement professionals. This report presents an overview of MnROAD products of interest at the local, state, and national levels. Furthermore, the report provides extensive references for these products in hopes of increasing awareness of MnROAD's under-publicized contributions to pavement engineering.

This field study involved falling-weight deflectometer (FWD) and dynamic cone penetrometer (DCP) testing on Minnesota roads using full-depth reclamation (FDR) base layers. The study also included basic backcalculation analysis of collected FWD data using TONN2010. This initial analysis found that FDR layers had an average stiffness, or elastic modulus, of 53.8 ksi and an average DCP Index of 2.81 mm/blow. The report presented these values alongside average DCP indices by location with limited analysis (more advanced analysis being beyond this field study). A more research-oriented review of the FWD and DCP data collected will be required to further verify layer thicknesses and compositions. The results of that review will enable MnDOT to better evaluate the use of DCP indices and the characterization of FDR-composed sublayers in MnPAVE-Flexible.

This report documents the development of an electronic dataset describing field and laboratory performance of unbound bases from 106 road sections containing recycled materials in Minnesota. This dataset provides a compact view of backcalculated layer properties (from falling-weight deflection data) per road section. This view includes summary statistics on backcalculated layer properties, estimates of possible errant data in raw deflection basins, associated laboratory resilient modulus (MR) values, and other brief but insightful measures that allow MnDOT research engineers to consider which road sections to include and exclude in determining a basis for MnPAVE Flexible material inputs.

This National Road Research Alliance (NRRA) study of MnROAD cold central-plant recycling (CCPR) sections investigated various design options for cold central plant recycling (CCPR) in low-volume road applications, where local engineers or contractors may rely on a stockpiled, single-source recycled asphalt pavement (RAP) as a quality cold-recycled layer for a paving project. Both the laboratory and field testing strove to characterize the cold-recycled (CR) layers as they performed in-situ. The field sections at MnROAD were intended to simulate low-volume road applications; therefore, the project endeavored to limit the preparation demands and characterization needs of the RAP stockpile. The laboratory tests determined that the MnROAD CCPR mixtures performed comparably to cold- recycled mixtures that were tested in other studies. Field study and observation determined that that chip-sealed CCPR lifts risk early rutting, whereas CCPR sections overlaid with 1.5" hot-mix asphalt (HMA) did not develop rutting.