Turgeon, Curtis M.

The intent of this report is to review the options available for treating cracks before more extensive repairs are needed. Recommendations are made where appropriate.

This report is a compilation of completed and soon to be completed asphalt: rubber studies undertaken by the Minnesota Department of Transportation (MN/DOT). The goals of each study vary with the manner in which the asphalt-rubber was utilized. Asphalt-rubber has been utilized in hopes of limiting reflective cracking by means of a stress absorbing membrane or a stress absorbing membrane interlayer. Using asphalt- rubber in a dense graded bituminous mixture was also attempted with the intent to limit reflective cracking while also resisting stripping due to greater film thickness rn1 the aggregate and greater impermeability to water. The Plus-Ride(TM) system of using granular rubber and a gap graded aggregate in a plant-mixed bituminous surface was employed in hopes of creating a self-deicing pavement. The results from these test projects vary from site to site but overall the Department: remains cautiously optimistic that asphalt-rubber can be an effective tool in pavement maintenance and reconstruction.

The proprietary product Verglimit claims to decrease the amount of materials and man-hours needed for snow and ice control while maintaining adequate safety levels. Verglimit consists of calcium chloride flakes encapsulated in linseed oil which are blended into the plant-mixed bituminous wearing surface. The manufacturer claims that exposed CaCl will attract moisture and form a solution which prohibits adhesion of snow and ice to the pavement. A Verglimit test section was constructed on U.S. Route 8 near Taylors Falls, MN. The applied mix appeared to be tender and some compactions difficulties were experienced. Manufacturer's recommendations were closely followed and no other unexpected difficulties occurred. Evaluation of the test section consisted of deicing observations as well as other pavement performance characterizations. Portions of the Verglimit overlay experienced shoving and were milled and replaced. Significant deicing benefits were not observed. No future Verglimit sections are planned.

The purpose of this study is to evaluate a rubber modified plant-mixed bituminous surface mixture. This mixture was produced using the patented process called "Plus Ride™" "Plus Ride™" is advertised as having unique de-icing properties, is durable and has the ability to reduce reflective and thermal cracking. This study is part of the FHWA Demonstration Project No. 3 "Asphalt Additives", and financed jointly by the U.S. Department of Transportation, Federal Highway Administration, and the Minnesota Department of Transportation. The authors wish to acknowledge the contribution of Districts 3 and 9 Construction and Materials personnel, and the Office of Materials Engineering for laboratory work and recommendations; Roger Olson, Research Operations Engineer; and Jerry Teig, Research Assistant. The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented. The contents do not necessarily reflect the official views or policy of Mn/ DOT or the Federal Highway Administration. This report does not constitute a standard specification or regulation.

The Minnesota Department of Transportation (Mn/DOT) has experimented with the use of shingle scrap in hot mix asphalt (HMA) since 1990. To date, the source of the shingle scrap has been shingle manufacturers exclusively. The manufactured shingle scrap consists primarily of tab punch-outs but also contains some mis-colored and damaged shingles. Test sections were constructed on the Willard Munger Recreational Trail, T.H. 25 in Mayer, Minnesota and on County State Aid Highway (CSAH) 17, in Scott County, Minnesota. Not only are the test sections performing as well as the control sections, but using shingle scrap reduces the amount of virgin asphalt cement required in a bituminous mix, thus creating the potential for a cost savings when using shingle scrap in HMA. Based on the performance of these lest sections, shingle manufacturing scrap is now an allowable salvage material in hot mix asphalt under Mn/DOT specification 2331.E2e, Recycled Mixture Requirements. This report outlines the history of shingle scrap use in Minnesota, presents laboratory and field performance data and contains the current Mn/DOT specification allowing shingle scrap to be used as a salvage material in HMA pavements.

The practice of sawing and sealing joints in pavements is not a new one. In fact, it is common practice in the construction of jointed Portland Cement Concrete (PCC) pavements. The idea of sawing and sealing joints in bituminous pavements is much less endorsed by those responsible for the construction and maintenance of hot mix asphalt (HMA) pavements. Minnesota began experimenting with sawing joints in HMA pavements in the late 1960's. Since then more than 50 test sections have been constructed throughout the State. Test sections include HMA overlays of Jointed Concrete Pavement, HMA overlays of HMA pavements and newly constructed HMA pavements. The results show that in over 76 percent of the test sections, the formation of cracking was controlled by the sawing of joints. The unsuccessful sections were those where a deep saw cut was not made, those where the existing joints were badly deteriorated and those where the underlying joints were poorly re-located. All of these factors can be minimized through proper project selection and good design. This study involves a review of these test sections, identifying any problems associated with the saw and seal procedure and gives recommendations for its use in Minnesota.

The Minnesota Department of Transportation is continually investigating ways to improve the cold temperature performance of its asphalt concrete pavements. One reported method is to modify the asphalt binder with ground reclaimed automobile and truck tire rubber. In 1984, a project on TH 7 (State Project 4703-17) was selected for the field trial of an asphalt-rubber cement dense graded concrete utilizing a product produced by Arizona Refining of Phoenix Arizona. Construction of the asphalt-rubber cement dense graded asphalt concrete required some special effort and specialized equipment to maintain adequate mixing and placing temperatures. Evaluations included crack counting, resilient modulus, inplace air voids rutting, roughness, recovered penetration and cost considerations. Interesting results regarding the resilient modulus of the asphalt rubber samples were found. However, the formulation used provided little or no perceived benefits to the roadway at much higher costs. The high costs were due in part to the nature of the project. However, this appears to be a cumbersome and expensive procedure with the primary benefit being waste tire utilization.

The need to reduce our states dependence on land fills resulted in a unique cooperative venture by three state agencies. A partnership was forged between the Minnesota Pollution Control Agency (MPCA), the Minnesota Department of Natural Resources (DNR) and the Minnesota Department of Transportation (Mn/DOT) to investigate the use of recycled tire rubber and processed asphalt shingle scrap. The result is a two mile section of the Willard Munger Recreational Trail in St. Paul, constructed with asphalt paving mixtures which contain varying percentages of recycled tire rubber and shingle scrap. Special bituminous mix designs were formulated using 3% rubber, 6% rubber, 3% rubber with 6% shingles and 9% shingles. The mixtures containing rubber did not exhibit acceptable mix characteristic values under present Mn/DOT bituminous specifications. The shingle-only mix met specifications and yielded an economic advantage of decreasing the asphalt cement demand of the mix. Conventional mixing and paving equipment was utilized for construction. This application appears to be a viable alternative containing rubber increased from 35% to 50% over the cost of the conventional mixture. Since the use of shingle scrap was negotiated by the private companies involved, no comparable cost data is available.