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Intelligent compaction (IC) is a roller-based innovative technology that provides real-time compaction monitoring and control. IC can monitor roller passes, vibration frequencies/amplitudes, and stiffness-related values of compacted materials or intelligent compaction measurement Values (ICMV). Various ICMVs have been introduced since 1978. Based on the five levels of ICMV in the 2017 FHWA IC Road Map, the current implementation of ICMV in the United States has been limited to Levels 1 and 2. However, Level 1 and 2 ICMVs fail to meet the FHWA IC Road Map criteria. To achieve the full potential of IC technology, Level 3 and above ICMVs are needed to gain the confidence of agencies and industry and the adoption of IC to soil and base compaction. This project aims to (1) evaluate Level 3-4 ICMV systems against Level 1 ICMV systems for soils, subbase, and base compaction and (2) develop a blueprint for future certification procedures of IC as an acceptance tool. This study also aligns with the goals of the ongoing HWA IC for foundation study and the TPF-5(478) pooled fund study. This final report details the ICMV background, field test efforts, analysis results, and an IC specification framework for compaction acceptance.

To address climate change mitigation goals, alternative concrete paving mixtures are being investigated that are claimed to have a lower global warming potential (GWP) at time of construction with equal or better long-term performance compared to conventional concrete paving mixtures currently in use by the Minnesota Department of Transportation (MnDOT). The objectives of this study are to develop a final matrix of test sections and a construction quality assurance (QA) plan for the construction of a Minnesota Road Research Facility (MnROAD) experimental section, consisting of 16 test cells, to assess the environmental impact and constructability of various concrete paving mixtures designed to reduce environmental impact, with the opportunity to assess in-service performance over a three-year period following test cell construction. This report documents the concrete mixtures being evaluated, the list of tests to be performed on the plant-produced concrete, construction observations, and a preliminary assessment of environmental impact. Follow-up studies are ongoing, which will document the lab testing results and provide yearly performance updates on the test cells. These reports will be made available by MnDOT.

This Phase 1 study was undertaken to evaluate cracking related to dowel bars and tie bars in concrete pavement. The results of the literature review and field studies suggest that under some conditions, restraint caused by dowel bars and tie bars in the concrete result in high early age stresses that contribute to cracking. Field evaluation of six sites conducted as part of this research suggests that this type of cracking is not an isolated phenomenon. While a notional description of the potential mechanism is described in this report, details regarding the extent to which various factors impact this type of cracking and appropriate reasonable steps to take to mitigate this type of cracking is not fully understood. To gain a more detailed understanding, a combination of finite element (FE) analysis with laboratory experiment is proposed for Phase 2. The analysis proposed includes an evaluation of key parameters and their influence on dowel bar cracking followed by validation through laboratory experimentation and model refinement.

This project aimed to validate loose mix aging procedures for cracking resistance evaluation of asphalt mixtures in balanced mix design (BMD) with a broad range of field projects covering various mixture components, pavement ages, and climatic conditions. To that end, a two-phase research approach was followed, with Phase I focusing on a literature review, research gap analysis, and development of Phase II work plan. The literature review topics included development and preliminary field validation of existing loose mix aging procedures; the impact of loose mix aging on asphalt binder and mixture properties; and effects of silo storage, mix hauling, mix reheating, specimen storage, and asphalt weathering on asphalt binder and mixture properties. The literature was then critically reviewed to identify research gaps that might hinder the implementation of loose mix aging for cracking resistance evaluation in BMD, including lab-to-field aging correlation, applicability to asphalt mixtures containing additives, selection of laboratory tests and parameters to assess loose mix aging, and implementation of loose mix aging into BMD. Finally, a Phase II work plan was developed to address the knowledge gaps identified through the literature review and research gap analysis, which include two major tasks: 1) further validation of 95°C loose mix aging maps, and 2) conversion of different loose mix aging procedures based on a kinetics aging model.

Asphalt pavements deteriorate from temperature cycling, moisture, oxidation, and loading-related distresses. Pavement preservation is critical in maintaining the functional and structural integrity of roads and extending pavement life. Surface treatments can prevent or restore the aging effects by rejuvenating and/or sealing the pavement’s surface, limiting further damage, and restoring its flexibility. This collaborative study of MnDOT, the National Road Research Alliance (NRRA), and Iowa State University investigates the efficacy of fog seal/bio-fog seal topical treatments based on soy-derived rejuvenators, epoxidized soybean oil (SESO), and BioMAG, which contains SESO and the biopolymer poly(acrylated epoxidized high oleic soybean oil) (PAEHOSO). Each topical treatment is applied at three locations in different asphalt binder grades to provide a comprehensive approach to their impacts on the dry time, reflectivity, friction, and permeability of the pavement course. It is observed that the bio-fog seal treatments improve the skid resistance of the pavement, do not affect the reflectivity of pavement markings, and are able to restore the stiffness of the asphalt mixtures. Additionally, the fog seals show fast setting and curing and allows the road to be open to traffic in less than 30 minutes.

This research investigated the effects of incorporating recycled concrete aggregate (RCA) at low replacement levels on the properties of concrete. Four different RCA sources were used, each with different aggregate properties. For each source, replacement levels of 5, 10, and 15% were tested and compared to a control group, which had no RCA. Of the four RCA sources investigated, three had similar levels of absorption capacity and percent fines, while one source had higher levels of both properties. RCA replaced virgin aggregate of a similar gradation and replacement was on the basis of volume. Fresh and hardened concrete properties were tested, including air content, super air meter (SAM) number, slump, workability via the box test, compressive strength, flexural strength, elastic modulus, Poisson’s ratio, coefficient of thermal expansion, surface resistivity, freeze-thaw durability, and unrestrained shrinkage. Digital image correlation was used to visualize strain fields during compression testing. A statistical analysis was conducted to determine if any observed differences in hardened properties between the test mixes and the control group were statistically significant. This research found that using up to 15% of an RCA with reasonable values of absorption capacity and percent fines would not negatively impact most concrete properties. It also provided an outline for future research to develop a specification to define what constitutes reasonable values of RCA properties for future use.

The use of roundabouts in rural areas of the US is growing rapidly. For roundabouts constructed with concrete pavement, joint layout can be especially challenging. To reduce the need for sophisticated joint layouts, consideration is being given to constructing roundabouts without joints and instead using structural fiber-reinforced concrete (FRC) to bridge any cracks that might occur. In 2018, Minnesota’s first jointless FRC pavement roundabout was constructed at the intersection of Minnesota Trunk Highway 4 and County State Aid Highway 29. The National Road Research Alliance (NRRA) sponsored a study to document the construction and performance of Minnesota’s first jointless FRC roundabout. One of the key objectives was to carry out a three-year performance monitoring regimen of the roundabout to better understand its in-situ performance when exposed to traffic loading and environmental conditions. This report documents the third-year performance of the roundabout as per the requirements of Task 3 of the work plan.

The overall objective of this study was to explore three novel rejuvenator application methods using the emulsion and foaming technologies and determine their impacts on the workability and long-term cracking resistance of high-reclaimed asphalt pavement (RAP) asphalt mixtures. To that end, a comprehensive experimental plan was developed, which consisted of four supplementary experiments focusing on rejuvenator characterization, foaming measurements of rejuvenators and rejuvenated asphalt binders, RAP pretreatment and marination evaluations, and mixture performance testing, respectively. Test results indicated that adding rejuvenators for RAP pretreatment improved the overall quality characteristics of RAP. Among the three rejuvenator application methods evaluated for RAP pretreatment, the emulsion method was found more effective than the spray-on and foaming methods. Marinating the pretreated RAP had a notable impact on the rheological and chemical properties of the extracted RAP binders, but it did not significantly affect the workability, appearance, and color consistency of RAP. Adding rejuvenators, in general, improved the workability and cracking resistance of high-RAP mixtures, although the improvement in mixture performance test results, in some cases, was not statistically significant. Among the different rejuvenator application methods, pre-blending the rejuvenator into the virgin binder (with or without foaming) provided slightly better or equivalent rejuvenating effectiveness and thus, mixture performance properties, than adding the rejuvenator for RAP pretreatment. Based on the findings of the study, it was recommended that asphalt contractors continue to use the pre-blending method of adding rejuvenators for the design and production of high-RAP mixtures due to performance and ease of operation considerations.

We provide a final summary report of the project executed during last 2.5-year period (January 2020 - June 2022). The project tasks are summarized in the following scope of work (SOW): • Task #1: Project Management and Administration • Task #2: Hardware Development (Seismic Data Acquisition System) & Testing • Task #3: Software Development & Testing • Task #4: Delivery and Demonstration of Seismic Data Acquisition System and Software • Task #5: Final Report Initial project development and its progress in tasks #1 - #3 have been summarized in the quarterly reports and updated every month on the dedicated website until the end of December 2021. This final report focuses on the delivery of the completed system and subsequent demonstration surveys (tasks # 4 and #5). Associated details are presented in Appendix I (delivery) and Appendix II (demonstration surveys). Background theories and historical development that led to this particular system are described in an expanded abstract submitted to Geo-Congress 2022 at Charlotte, NC, March 20-23, 2022, which is attached in Appendix III. The developed system is named "TAPPER 64," and it consists of four (4) 16-channel receiver arrays that are transversely arranged to survey a certain width of the pavement (e.g., 0.5-m) simultaneously. Detailed technical and operational contents in hardware and software components of TAPPER 64 are presented in the "TAPPER 64-User's Manual" attached in Appendix IV.

The air void system in concrete provides a strong influence on the behavior of cementitious materials in both the fresh and hardened state, especially as it relates to freeze-thaw resistance and deicer scaling. The most common test procedure to characterize the air void system is ASTM C457 – Standard Test method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete, which involves microscopic determination of the air content, paste content, air-void size distribution, and spatial dispersion of a sawn concrete sample. This procedure is reliant on the user to make hundreds of critical decisions per sample, which requires significant time, and is potentially subject to human error. Additionally, ASTM C457 provides minimal guidance regarding the exact steps and equipment necessary to prepare a sample for evaluation. The outcome of this research not only provides specific information regarding sample preparation for hardened concrete air void analysis, it also develops an alternative characterization technique that drastically minimizes evaluation time, human error, and increases reliability of key hardened air void characterization parameters. Specific results show on average air void difference of 0.5% and 0.7% between the alternative method versus ASTM C457 Procedure A and B, respectively. The results also show a significant reduction of analysis time from approximately 2 – 4 hours per sample to 15 minutes per sample when using the alternative method.