Search Content

A total of 12 sealant products were applied on the Smith Avenue High Bridge in St. Paul and evaluated over a three-year period. Details, such as surface preparation and application methods, were documented for each product and are conditions specific to each product. Sealant performance was evaluated through field permeability testing, visual observations, and petrographic examination. Visual observations provided evidence that approximately 67 percent of test sections were performing effectively after one winter but only 4 percent after two winters. After three winters, 58 percent of the test locations were visually characterized as ineffective and 42 percent as partially effective. Product performance significantly reduced over the third winter, primarily due to major loss of sealant and surface sand materials. Coring was performed after the second winter, and the cores were photographed and subjected to a petrographic evaluation. The observed depth of sealant penetration was highly variable and likely is dependent on the presence of debris within the crack, original crack width, and the deck temperatures during application. The predominant failure mode observed under magnification was detachment from the crack face and not within the sealant materials. Based on numerous factors, four epoxy and three methacrylate products were recommended for consideration on MnDOT's Approved Products List. Each product recommendation contains the surface preparation and application method conditions under which they were applied. It is also recommended that MnDOT look into increasing the frequency of its routine crack sealing maintenance program from the current five-year cycle.

Tire Derived Aggregate (TDA) is referred to in this report as rough shreds, shreds, and tire chips of various sizes. The potential uses discussed herein include TDA as lightweight fill, retaining wall backfill, insulation layer, drainage layer, and capillary moisture break. Other uses exist; however, they are beyond the scope of this report. This report summarizes the results of numerous studies regarding the environmental concerns of using TDA both above and below the ground water table. The summary provides general observations based on the literature review performed, comments on the current state of the practice regarding the use of TDA for highway applications, and information on additional resources.

The Minnesota Department of Transportation's (MnDOT) concrete pavement design procedure, RigidPave, is based on the 1981 American Association of State Highway and Transportation Officials (AASHTO) Interim Guide and is entirely empirically-based. The American Cement Pavement Association (ACPA) developed StreetPave based on the Portland Cement Association (PCA) thickness design method with updated information, including a new fatigue model. This study compared RigidPave to StreetPave with a review of the input variables and design inputs used by surrounding departments of transportation. Existing thin (six inches or less) concrete pavements were also evaluated, which included both city and county pavements and test cells at MnROAD. There are two primary differences between the RigidPave and StreetPave: 1) traffic is handled differently and 2) the underlying design methodology. Both are based on time-tested and proven design methodologies and provide generally similar designs. The predicted design lives of the doweled low-volume cells at MnROAD appear to be similar using either StreetPave or RigidPave. The examples provided by cities and counties typically did not contain enough known information, and therefore, required too many assumptions for analysis. The authors recommend that StreetPave is added as an alternate concrete pavement thickness design procedure for city and county projects in Minnesota. Use of the StreetPave is currently allowed by the Virginia Department of Transportation for design of secondary roads. It was also determined that RigidPave has a built-in reliability of approximately 89% due to a factor of safety that is applied to the modulus of rupture. An alternate approach to allowing StreetPave as a design option would be to incorporate the reliability knowledge of RigidPave learned as part of this project.

As Portland cement concrete (PCC) pavements age, longitudinal and transverse joints can exhibit signs of distress as a result of traffic loading, climatic variations, materials-related issues, and construction defects. Although only small areas are often involved, the joint distress can substantially disrupt traffic flow and increase pavement roughness, sacrificing consumer ride comfort. When immediate action is required, temporary repairs are often made using readily available materials, such as cold mix or other asphalt materials. These temporary materials are often replaced with more permanent materials to reestablish the integrity and functionality of the concrete pavement. The goal of this project is to provide a guide for agencies to establish an effective joint repair program. The final report reviews the background information explaining why this research was performed, summarizes the findings from previous similar research studies, details how the patches were constructed and how they performed, and provides a Product Matrix that includes installation requirements, equipment needed, along with the life expectancy of the products to compare and guide the reader through product selection.

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.

MnDOT's current pavement thickness design procedures do not characterize the effects of subgrade soil frost susceptibility. Previous research indicates frost action is the most severe environmental factor on pavement performance. The most accepted mitigation practice is to replace the frost-susceptible material with non-frost-susceptible material to a depth of one-half or more of the frost depth; with silt soils possessing the highest potential for frost heave. MnDOT currently requires minimum total depths of 30 or 36 inches of "frost-free" materials (FFM) for flexible pavements. Limited conclusions with regard to subgrade frost action could be drawn from MnDOT's pavement performance data. Data from the Long-Term Pavement Performance (LTPP) program SPS-8 sites in South Dakota and Wisconsin suggest that lesser FFM depth and greater subgrade silt content correlate well with poorer performance. Data regression based on nine freezing climate zone SPS-8 sites provide a very good fit and a simple-to-use design tool is based on project location; predicted frost depth; and subgrade soil silt content. The required percentage treatment of the predicted frost depth ranges from about 30 percent (0 percent silt) to over 80 percent (100 percent silt). The tool provides a straightforward means to select frost treatment depth that is simple and cost effective to implement; requires limited additional laboratory testing; and requirements are generally in line with MnDOT's current practices. Short-term and long-term recommendations are provided to help MnDOT expand on the results of this project.