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This study evaluates the use of seal coating as a method to protect bituminous pavements from oxidation, water infiltration, and raveling. The Minnesota Department of Transportation (Mn/DOT) applied seal coating to a roadway segment of Trunk Highway 21 in August 1998. The report outlines optimal requirements for the application of seal coat. Cost comparisons of the test sections are also presented. Mn/DOT will continue to examine the test strip for performance and provide regular updates until the strip's condition requires reconstruction or overlay.

This project introduced the use of micro surfacing as a pavement preventive maintenance surface treatment and tested different methods of using micro surfacing to correct or prevent defects in existing pavements. Micro surfacing mixtures include polymer-modified emulsified asphalt cement, a well-graded 100% crushed mineral aggregate, and mineral filler, such as portland cement or hydrated lime, with water and control additives added to control the speed of breaking and workability. Micro surfacing remains semi-liquid during mixing and placing phases and then cures chemically for a very durable asphalt surface treatment. Application and testing revealed that the fast-moving micro surfacing process minimizes the amount of down time for traffic; does an excellent job of reestablishing cross sections; fills ruts; improves ride quality; increases friction numbers; and provides an excellent background for pavement markings. It does not seal reflective cracks, has generated some concerns about increased traffic noise, and does not work favorably for smoothing humps in pavement. Overall, project selection played a key factor in the overall success of micro surfacing. A very thin surface treatment, microsurfacing cannot be expected to fix structural problems in existing pavements. One should avoid using micro surfacing on roadways that are still rutting and repair potholes before placement of micro surfacing.

The Minnesota Department of Transportation (Mn/DOT) has concluded a research study on the proper techniques involved in seal coating. A key part of the research project involved performing seal coat designs using the procedure developed by Norman McLeod. In addition, research personnel were present on many seal coat construction projects assisting the inspector and contractor. The primary purpose of this handbook, revised in 2006, is to provide a solid background in seal coat materials, equipment, design and construction for the field inspector. Divided into two main sections, this updated handbook provides direction for designers and field personnel. Thomas J. Wood handled this revision. The original work was prepared by David W. Janisch and Frank S. Gaillard. NOTE: A revised version of Minnesota Seal Coat Handbook was published in December 2022 (report 2022-22).

This report presents a summary of pavement preservation activities and recommended uses, expected longevity, and expected pavement life extension. It also includes some basic information intended to be used by those less familiar with pavement preservation, pavement management, life cycle cost analysis, cost estimating, contracting methods and others to help inform and educate in this important aspect of pavement engineering. Tools and techniques are presented to assist local agency engineers in evaluating costs, benefits, timing, longevity, and the decision-making process for developing an effective pavement preservation program on an individual pavement segment or over an entire network. The report includes examples using real pavement engineering data from several cities and counties in Minnesota to demonstrate topics such as activity timing and the benefits of a preventive maintenance plan rather than a reactive one. A set of guidelines was developed as part of the associated project intended to serve as reference material and as a training program.

Recycled Asphalt Shingles (RAS) include both manufacture waste scrap shingles (MWSS) and post-consumer tearoff scrap shingles (TOSS). It is estimated that Minnesota generates more than 200,000 tons of shingle waste each year. Recently, a portion of this waste has been incorporated into hot-mixed asphalt (HMA) pavement mixtures. The current technology limits the amount of RAS in HMA to no more than 5 percent by weight. This leaves a lot of underutilized shingle waste material throughout the state. This has prompted MnDOT to investigate other potential uses RAS. One potential use is to improve the performance of gravel surfacing and reduce dust by replacing common additives such as calcium chlorides with RAS. This is especially relevant as gravel sources in Minnesota have been depleted and/or have declined in quality, which has affected the performance of gravel surfacing. These poorer quality fines can increase the amount of dust generated and increase the difficulty of keeping the roadway smooth. Some agencies have used dust control additives to help the performance of these lower quality gravels. Successful implementation has the potential of removing valuable RAS materials from the waste stream to supplement the use of more expensive virgin materials and improve the performance of local roads.

The higher costs of hot-mix asphalt pavement are causing more agencies to choose pavement preservation techniques to maintain their pavements. Some agencies have experienced stripping of the asphalt surface under chip seals, this distress appears to occur mostly in urban areas on curb and gutter streets. The main objective of the study was to determine what causes the stripping and to develop test methods to determine if the street will strip prior to placement of the chip seal. Both field and lab methods were used. Research focused on determining air voids, permeability, and density of the samples. Once these were determined, correlations were developed to determine the conclusions.

The growth in recreational trails owned by the State, Cities, Counties, and Park systems over the last 20 plus years has exploded. Most if not all efforts related to recreational trails over these years has been focused on construction of new trails. There have been little organized efforts in trail preservation and or preventive maintenance (PM) methods to extend the usable life of the trails. The agencies that have a PM programs for their recreational trails rely on treatments that started out as highway or street treatments that may have been modified for use on the trails. The goals of this research project where to study existing treatments, how effective they are, promote new methods, and promote regular scheduled PPT for preserving trail systems.

Highway agencies have constructed expansive networks of pavements that are vital to the economic prosperity and vitality of the nation. These networks are currently deteriorating at such a rate that most agencies cannot afford to reconstruct them in a timely manner. Consequently, many agencies have employed low-cost preventive maintenance (PM) techniques such as crack and surface treatments in an attempt to slow the deterioration rates of the pavements, thus extending the service life and delaying the time until reconstruction. This study sought to address whether or not recent advances in bituminous mixtures and binder selection through SuperPave necessitated a re-examination of current PM practices. In other words should SuperPave pavements be managed differently, compared to other mixture types in the network. The first project task sought to analyze the effectiveness of PM treatments by using historical pavement management data to develop pavement decay curves with time. The results of the analysis indicated a life extension; however due to data limitations, a life cycle cost analysis (LCCA) as well as a specific life extension value were not conclusively determined. The second project task assembled a pavement owner's manual to provide general guidance on applying PM treatments throughout a pavement's life. The recommendations of applying PM are based primarily on the pavement's age and general surface characteristics. The recommendations of task 2 are based upon experienced engineering judgment, empirical evidence and a literature review; consequently they must be tempered to the local conditions, environment and materials.

Many governments and agencies responsible for the maintenance of local street systems have been applying low cost preventive maintenance (PM) treatments to their pavement network to extend pavement service life and reduce costs. Chip seals have become a popular PM treatment for these local streets; however cul-de-sacs have historically been less receptive to the treatments due in part to their geometry. This has caused many agencies to stop chip sealing their cul-de-sacs which not only creates a non-uniform appearance, but leaves the pavement more vulnerable to environmental induced damage. As an alternative to chip seals, fog seals can be considered as a PM treatment for cul-de-sacs.

The growth in recreational trails owned by the State, Cities, Counties, and Park systems over the last 20 plus years has exploded. Most if not all efforts related to recreational trails over these years has been focused on construction of new trails. There have been little organized efforts in trail preservation and or preventive maintenance (PM) methods to extend the usable life of the trails. The agencies that have a PM programs for their recreational trails rely on treatments that started out as highway or street treatments that may have been modified for use on the trails. The goals of this research project where to study existing treatments, how effective they are, promote new methods, and promote regular scheduled PPT for preserving trail systems.