This review was part of ongoing research to determine how Bituminous over Concrete (BOC) pavement cracks, and how to reduce or eliminate cracking of the Hot Mix Asphalt (HMA) overlay
Preventive maintenance is defined by AASHTO as “a planned strategy of cost-effective treatments to an existing roadway system that preserves the system, retards future deterioration, and maintains, or improves the functional condition (without adding additional structural capacity)”. Thus a treatment used as a stop-gap measure to hold together a distressed pavement would not be considered a cost effective PM treatment. The AASHTO definition encourages a paradigm shift away from a reactive mindset that responds to distresses in the pavement, toward a proactive one that seeks to prevent, or reduce the occurrence of distresses by selecting the right road and using the best methods at the proper time.
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.
To demonstrate and test the concept of stabilized full depth reclamation as pavement base material, Full Depth Reclamation (FDR) with asphalt emulsion re-uses the existing asphalt mixture and adds stabilized additive to further increase material stiffness. This method was applied on three (3) cells located on the MnROAD mainline (Cells 2, 3 and 4).
On November 13, 2008, I reviewed the section of Interstate 35 southbound just north of junction with Interstate 90. The reason for reviewing this section is the following excerpted from report “Field Observations of the Coring of I-35 Between Mile Post 18 and 16 Southbound” Jerry Geib and Thomas Wood September 27, 2005. (Appendix A) This review is on going research to determine how Bituminous over Concrete (BOC) pavements crack, and how to reduce or eliminate cracking of the Hot Mix Asphalt (HMA) overlay.
The longitudinal construction joints on this segment of roadway, Interstate 494 from Mile Post 2.143 to Mile Post 7.461 in both directions a three to four lane divided urban freeway, had deteriorated to the point that they were a possible safety issue, especially for motorcyclist. The Metro District maintenance forces had tried different methods of patching the longitudinal joint failure. The methods tried are either very expensive or leave poor driving surface. The decision was made to try using the Micro Surfacing technology to see if this would fill the joints and leave a smooth durable driving surface. The intent of the project was to repair the right fog line and the two skip lines that where exhibiting failures.
The flexible slurry system is a mixture of emulsified asphalt, high quality crushed aggregate, and water. Depending upon the design, flexible slurry can be used in place of a blade leveling course prior to bituminous overlay or as a wear course. Flexible slurry is constructed using a micro surfacing machine, but is less brittle than a usual micro surface mixture. Historically Minnesota has used one type of emulsified asphalt (PG 64-22); but recent experimentation with binder grades shows that enhanced rutting and cracking performance is possible. Low speed traffic can aid in the curing and consolidation of flexible slurries.
This is the second revision of this handbook which was originally published in 1998. This update to the handbook, although still titled Minnesota Seal Coat Handbook, has changed all references of Seal Coat to Chip Seal, better aligning it with other state Departments of Transportation (DOTs), Federal Highway Administration (FHWA), and industry. Minnesota Department of Transportation (MnDOT) specifications will eventually be updated to reflect this change. As preventive maintenance and preservation of bituminous pavements continues to evolve, this version of the handbook has been expanded to include a brief discussion on spray applied bituminous surface seals and additional similar types of thin bituminous pavement surface treatments which are often referred to as BSTs.
