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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.

The variations in electromagnetic and electric properties with the moisture content of several geomaterials were assessed in this report to demonstrate their viability in estimating the moisture content of compacted geomaterials. A prototype device was also designed and fabricated to estimate the moisture content of compacted geomaterials by measuring the complex resistivity (amplitude and phase shift between the voltage and current) of geomaterials over numerous frequencies. Two fine-grained soils, two sandy soils, and two coarse-grained geomaterials were selected as a baseline for laboratory measurements. These soils were compacted and tested to measure their dielectric constants, traditional resistivities, and their complex resistivities using the developed prototype. The dielectric constants were less sensitive and more uncertain to the moisture content variations than the resistivity values. The traditional and complex resistivity measurements showed promise in the laboratory. The same soils’ seismic moduli, unconfined compressive strengths, and lightweight deflectometer moduli were also established. For field implementation, a rolling four-electrode equatorial array was created and tested within the laboratory and MnROAD facility. Field polarization and deviation from expected voltages and currents occurred frequently. These results suggested that resistivity or complex-resistivity measurements with rolling four-electrode arrays may need significant improvement for controlling moisture content.

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.

Concrete overlays of full depth reclamation (FDR) are a pavement rehabilitation option involving reclamation of existing pavement layers while providing a new concrete surface to the roadway. This report reviewed nine concrete overlays of FDR that have been constructed in three states since 2006. Design and construction details were collected for each project and performance was analyzed through automated pavement condition data. Additional distress surveys and testing, including falling weight deflectometer (FWD) testing, were performed at one project in Freeborn County, MN, to further characterize the pavement condition and structural properties. Overall, the projects reviewed in this study were performing well to date, and concrete overlays of FDR appear promising as cost-effective, sustainable tools for helping agencies maintain their pavement network.

This study evaluated the impact of polymer modification, without changing the base binder, on the intermediate-temperature cracking resistance of asphalt mixtures characterized using the Indirect Tensile Asphalt Cracking Test (IDEAL-CT) and the Illinois Flexibility Index Test (I-FIT). Twelve asphalt mixtures prepared with two mix designs and six virgin binders (including two unmodified and four polymer-modified asphalt binders per mix design) were evaluated. Each mixture was tested at three binder contents and two temperatures: 25°C and an equal stiffness temperature (T=G*). In almost all cases, the polymer-modified asphalt (PMA) and unmodified mixtures with the same base binder had statistically equivalent IDEAL-CT and I-FIT results, indicating a lack of sensitivity to polymer modification. Increasing the binder content or adjusting the test temperature to T=G* did not discriminate the PMA and unmodified mixtures in the two tests. Interaction diagram analysis of the IDEAL-CT and I-FIT results showed that polymer modification generally affected the toughness and post-peak behavior of the mixture, but these effects tended to offset each other on the final cracking index parameters. Unlike the IDEAL-CT and I-FIT, the two cyclic loading tests evaluated in the study demonstrated the benefits of polymer modification. This discrepancy highlighted the potential limitation of the monotonic loading tests in assessing the fatigue cracking resistance of PMA binders and mixtures. Finally, asphalt binders extracted from the PMA versus unmodified mixtures with the same base binder showed distinctly different rheological properties, but these differences were not captured in the IDEAL-CT or I-FIT when the test variability was considered.

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.

Real-Time Smoothness (RTS) measures pavement surface profiles during paving using sensors mounted on the back of a paver. The Federal Highway Administration (FHWA) has supported implementing RTS technology for concrete pavements through the SHRP2 Solutions program since 2014. Its study indicated that RTS technology's real-time diagnosis allows changing the paving operation to improve smoothness. This "proof-of-concept" research study aims to extend concrete RTS technologies to asphalt paving applications. The field demonstration results from two field projects show the feasibility of using asphalt Real-Time Smoothness (ARTS) to capture the roughness from various paving events. These results indicate some limitations of the ARTS prototype's measurements since the sensors were uncertified and mounted on a paver screed. The lessons learned from the demonstration projects are valuable for future ARTS technology and for further studies to improve asphalt pavement smoothness.

The National Road Research Alliance (NRRA); a multi-state pooled-fund program; exists to provide strategic implementation of pavement engineering solutions through cooperative research. NRRA is led by an Executive Committee of state DOT partners; and supported by numerous agency and industry partner representatives. Members provide expertise to NRRA; from the selection of research topics; to communication; and implementation. NRRA consists of five project teams: Flexible; Rigid; Geotechnical; Preventive Maintenance; and Technology Transfer. The 2017 construction season at MnROAD saw construction of 35 new and unique pavement test sections. The sections; designed to address NRRA high-priority research topics; were conceived and planned by NRRA project teams. This report details development; design; and construction of each research project and the test sections supporting them. Individual study details are left to future reports generated by the individual research contracts and their respective teams.

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.