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Full-depth reclamation (FDR) as a rehabilitation method improves the service life of pavement structures by reusing asphalt materials, thereby reducing costs and allowing for conservation of nonrenewable resources. However, the lack of mechanicsbased material testing procedures and performance-based specifications limit the use of FDR processes. First, the FDR design and construction process are presented, then, a literature review focusing on FDR research is completed, and a survey is conducted to obtain relevant information regarding current FDR practices in Minnesota. Next, Indirect Tensile Test (IDT) and Dynamic Modulus Test in IDT mode testing is performed on four FDR materials: Field mixed, Lab compacted; Lab mixed, Lab compacted; FDR with cement additive; and FDR with graphene nanoplatelet (GNP) additive. Two curing times are used to determine how physical properties change over time. Test results are used to perform simulations in MnPAVE software and a Life Cycle Cost Analysis (LCCA). Laboratory observations indicate that cement additive reduces predicted life and increases critical cracking temperature with a slight increase in cost; GNP additive reduces predicted life but also reduces critical cracking temperature with a significant cost increase; Lab mixed samples performed better than Field mixed, suggesting that field methods could be improved; and curing has a positive effect on the FDR materials with cement and GNP additives--for both materials, the dynamic modulus increase, and the GNP samples also had a slight increase in tensile strength. MnPAVE simulations and LCCA results indicate that over a 35-year period, FDR may be a more cost-effective method than traditional mill and overlay.

Pavement preservation is playing an increasingly significant role in maintaining our aging pavement infrastructure. One important component is the application of sealants to the pavement surface. In a joint study between MnDOT and the University of Minnesota, the field performance and mechanical properties of asphalt mixtures from pavement sections treated with a number of new products, called bio sealants, is investigated. The objective of the study is to obtain relevant properties of treated asphalt materials to understand the mechanism by which sealants improve pavement performance. Laboratory testing was performed on treated asphalt binder and mixtures. For binders, a dynamic shear rheometer and a bending beam rheometer were used to obtain rheological properties of treated and untreated asphalt binders. Field cores from both untreated and treated sections were collected and thin beam specimens were prepared from the cores to compare the creep and strength properties of field-treated and laboratory-treated asphalt mixture. It is observed that the oil-based sealants have a significant softening effect on the control binder compared to the water-based sealants. For asphalt mixtures, different trends are observed for the field samples compared to the laboratory prepared samples. Similar to binder results, significant differences are observed between the asphalt mixtures treated with oil-based and water-based sealants, respectively. From the analysis performed on the bending creep and strength results at low temperature, it is concluded that the application of sealants in the field have no significant effect on these properties. Fourier transform infrared spectroscopy (FTIR) analysis showed that the sealant products could not be detected in mixture samples collected from the surface of the treated section.

Significant resources can be saved if reactive type of maintenance activities are replaced by proactive activities that could significantly extend the pavements service lives. Due to the complexity and the multitude of factors affecting the pavement deterioration process, the current guidelines for applying various maintenance treatments are based on empirical observations of the pavement surface condition with time. This report presents the results of a comprehensive research effort to identify the optimum timing of surface treatment applications by providing a better understanding of the fundamental mechanisms that control the deterioration process of asphalt pavements. Both traditional and nontraditional pavement material characterization methods were carried out. The nontraditional methods consisted of X-Ray Photoelectron Spectroscopy (XPS) for quantifying aging, while for microcracks detection, electron microprobe imaging test (SEM) and fluorescent dyes for inspection of cracking were investigated. A new promising area, the spectral analysis of asphalt pavements to determine aging, was also presented. Traditional methods, such as Bending Beam Rheometer (BBR), Direct Tension (DTT), Dynamic Shear Rheometer (DSR) and Fourier Transform Infrared Spectroscopy (FTIR) for asphalt binders and BBR and Semi-Circular Bending (SCB) for mixtures were used to determine the properties of the field samples studied in this effort. In addition, a substantial analysis of measured pavement temperature data from MnROAD and simulations of pavement temperature using a one-dimensional finite difference heat transfer model were performed.

Good fracture properties are an essential requirement for asphalt pavements built in the northern part of the US and in Canada for which the predominant failure mode is cracking due to high thermal stresses that develop at low temperatures. Currently, there is no agreement with respect to what experimental methods and analyses approaches to use to investigate the fracture resistance of asphalt materials and the fracture performance of asphalt pavements. This report presents a comprehensive research effort in which both traditional and new experimental protocols and analyses were applied to a statistically designed set of laboratory prepared specimens and to field samples from pavements with well documented performance to determine the best combination of experimental work and analyses to improve the low temperature fracture resistance of asphalt pavements. The two sets of materials were evaluated using current testing protocols, such as creep and strength for asphalt binders and mixtures as well as newly developed testing protocols, such as the disk compact tension test, single edge notched beam test, and semi circular bend test. Dilatometric measurements were performed on both asphalt binders and mixtures to determine the coefficient of thermal contraction. Discrete fracture and damage tools were utilized to model crack initiation and propagation in pavement systems using the finite element method and TCMODEL was used with the experimental data from the field samples to predict performance and compare it to the field performance data.

Pothole repairs continue to be a major maintenance problem for many highway agencies. There is a critical need for finding long-lasting; cost-effective materials and construction technologies for repairing potholes. This research effort investigates critical components associated with pothole formation and pothole repair and proposes solutions to reduce the occurrence of potholes and increase the durability of pothole repairs. The components include investigating and documenting pavement preservation activities; experimental work on traditional repair materials as well as innovative materials and technologies for pothole repairs; stress analysis of pothole repairs to identify whether certain geometric configurations are more beneficial than others; evaluating cost analyses to determine the effectiveness of various repair methods. A number of conclusions and recommendations were made. Potholes are mainly caused by the delayed response to timely fixing common pavement distresses. The state of Minnesota has a number of preservation strategies that are available and have been successfully used. Recommendations are made to improve these strategies using documents made available as part of new Every Day Counts; EDC-4; initiative. Currently; there are no required specifications for patching materials. Mechanical testing can be used to select patching materials based on the estimated durability of the pothole repair; such as short-; medium-; and long-term. A number of new materials and technologies are available for more durable solutions for winter pothole repairs; however; they require additional heat source and are more expensive.