Pantelis, John

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.

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.

An Otta seal is an asphalt surface treatment constructed by placing a graded aggregate on top of a thick application of relatively soft bituminous binding agent. Minnesota has used emulsified asphalt exclusively (HFMS-2s); it could be constructed with cutback asphalt if desired. The binder works its way into the aggregate with rolling and traffic. In comparison to other surface treatments, material and construction specifications are not as strict. Local aggregates that would not meet the requirements for high quality paving aggregate are often used in Otta seals.

This Technical Summary relates to Report 2007-34, "Implementation of Ground Penetrating Radar," published August 2007.

This report contains the appendices to Report 2007-34, Implementation of Ground Penetrating Radar

This report summarizes lessons learned in evaluating the bonding strength of hot mix asphalt (HMA) layers. Testing included: determining an optimal range for the bond strength of a tacked hot mix asphalt interface, and implementing the findings. The research method used a Florida Bond Test fixture along with a Marshall asphalt mixture testing load frame to evaluate tack bond shear strength and deformation. Specimens were obtained from state, county and city paving projects from around Minnesota. Results were compared to related research conducted in the United States. Recommendations for a tack bond test program: Equipment includes the Marshall load frame already used by many HMA laboratories, HMTS software or similar, and the Florida Bond Test apparatus. Follow Minnesota modifications of Florida Bond Test protocol. Compute the average and standard deviation of peak shear stress from specimen sets. Cores exhibiting layer separation during coring or during removal will be included in the specimen set and assigned a peak shear stress of 0 psi. Average peak shear stress will be 100 psi or greater. The standard deviation of peak shear stress will be 25 psi or less.

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.

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.

The objective of this project was to demonstrate the capabilities and limitations of ground penetrating radar (GPR) for use in local road applications. The effectiveness of a GPR survey is a function of site conditions, the equipment used, and experience of personnel interpreting the results. In addition, not all site conditions are appropriate for GPR applications. GPR is a nondestructive field test that can provide a continuous profile of existing road conditions. GPR utilizes high-speed data collection at speeds up to 50 mph, thus requiring less traffic control and resulting in greater safety. GPR has the potential to be used for a variety of pavement applications, including measuring the thickness of asphalt pavement, base and sub-grade; assisting in the analysis of rutting mechanisms; calculating and verifying material properties; locating subsurface objects; detecting stripping and/or layer separation; detecting subsurface moisture; and determining depth to near-surface bedrock and peat deposits. These applications are discussed in reference to 22 projects completed throughout the State of Minnesota.