Watson, Mark J.

Rises in construction and asphalt binder costs, as well as the growing pressures on landfills, have contributed to the increased use of tear-off scrap shingles (TOSS) and manufacturer waste scrap shingles (MWSS) into hot-mixed asphalt (HMA) pavement mixtures. This research project was undertaken to address the responsible incorporation of recycled asphalt shingles (RAS) into HMA pavement mixtures to ensure environmental benefits are realized and pavement durability is retained or improved. The research consisted of a literature review, extensive laboratory testing and field evaluations of in service RAS/RAP HMA pavements. Binder testing established a strong correlation between the new asphalt binder to total asphalt binder ratio and the extracted high/low binder performance grade temperatures. Dynamic modulus testing on HMA mixtures proved to be an invaluable tool in comparing the effects of RAS and RAP on mixture properties across a wide range of temperatures. Field performance appeared to validate the laboratory findings in some instances.

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.

Rumble strips are a cost effective safety treatment for rural pavements, however they allow water to pool and increase the surface area of the pavement exposed to the elements. This research sought to address the maintenance effects of rumble strips on HMA pavements and what effect, if any, these have on the service life of the pavement. A survey was conducted which found that most respondents either noted the presence of distresses in rumble strips, or were concerned that the rumble strips were the direct cause of distresses. Next this study recommended several treatment options for pavements with rumble strips. Many of these recommendations are anecdotal and based on engineering judgment, which underscores the need for additional research. The recommended preventive maintenance treatment is to use construction funds to apply a cationic rapid set polymer modified diluted (CRS-2pd) fog seal over the entire shoulder, including the rumble strips. This will ensure an initially sealed surface and provide the maximum benefit in terms of service life extension. Crack sealing, although not an integral part of preventive maintenance for rumble strips should be applied to the adjacent cracks to slow the growth of cracks into ground in rumble strips.

Concrete pavements built in Minnesota are currently textured by dragging an inverted Turf or broom in the longitudinal direction. This process imparts a macro texture required to be greater than a mean texture depth of 1mm measured by the ASTM Sand Volumetric test (ASTM E 965-95). At present, this texture guideline is communicated through a special provision in pavement construction. Newly textured pavements are usually evaluated for adequacy in providing a safe riding surface through texture measurements for acceptance and friction measurements as required. The current FHWA Technical Advisory on Texture requires that performance of non-conventional textures be monitored and reported. This report identifies pavement sites in the network where the original texture, mainly the transverse tining plus Burlap, was either overlaid or rebuilt and the new surface finished with longitudinal inverted turf drag, or broom drag. It extracts wet weather accident data from the Mn/DOT Office of Traffic, Safety and Operations (OTSO) database and analyzes the annual wet weather accident and crash rates, preconstruction, during construction and after construction. It performs a descriptive statistics of the period before and the period of the new texturing to determine if, wet weather accident counts, percentage of wet weather accidents in total count and crash rates and /or ratio of annual wet to dry accident counts, and crashes clearly increased with current texturing practices. Data was analyzed with statistical tools for data comparison including the descriptive statistics, U-test & and "before and after" comparison (Z-test). The analyses of the data for the sections show that current texturing practices did not cause an increase in the annual wet weather accidents, crash rates, or ratio of wet to dry weather accidents.

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.