Agenda - Council - 02/11/2020 - Laserfiche WebLink

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Introduction: In recent years, Mn/DOT has received reports of stripping, or deterioration, of the upper'/2 to 1 inch of hot mixed asphalt (HMA) pavements under chip seal surface treatments. This distress (Figure 4) usually starts out as a small blister and develops to small potholes, at which point the chip seal delaminates from the pavement. These distresses can become an expensive maintenance problem. These distresses could also impede the deployment of cost saving preventive maintenance (PM) treatments if the treatments are viewed as the cause of the distresses. Figure 1. Early stage of HMA deterioration under a chip seal (251 Reid). This report represents task 1 of the Minnesota Local Road Research Board (LRRB) project number 2010-042, entitled, "Stripping of Hot Mixed Asphalt Pavements under Chip Seals". The overall goal of this research project is to determine the underlying cause of the stripping distresses, identifying which pavements are at greatest risk and implement risk mitigation strategies that include improved specifications and practices. The main purpose of this task report was to identify the extent of the problem among local government entities. Minnesota cities and counties were asked to complete an online survey, using the Survey Monkey TM tool, describing their experience with the stripping under chip seal distress. Appendix A is a draft of the survey that was used to populate Survey Monkey TM. The survey opened for response in early September and received 66 responses. Findings and Observations: The survey responses show that the problem of stripping of the HMA under a chip seal happens in over 60% of the agencies that responded. The first chip seals were applied when the streets were between four (4) and eight (8) years of age. The distress seems to appear between two (2) to four (4) years after chip seal application. Note that 60 percent of respondents reported that they did not have un-chip sealed roadways the same age as the chip sealed roadways. The ninth question asked for comments. Appendix A lists all the comments received. Below are a few selected comments. A-2