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

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from field testing, not all roads with chip seals exhibited stripping. Information provided by city engineers for field sites locations identified less than Moderate levels of stripping in 6 of the 18 primary field sites. Condition information relative to volumetric core data (percent air voids and maximum density) is described in Figure 12. 10 9 8 7 cn6 5 Q 4 3 2 1 0 150 151 152 153 154 155 156 157 Max Density (pcf) Figure 12. Severity of stripping in chip -sealed pavements in 18 locations with maximum theoretical density and percent air voids Severity of Stripping ::Low o Low to Moderate O Moderate Moderate to High •High • • 0 • • • 0 0 0 • 0 Figure 12 does not describe an observable trend relating the extent of stripping to air void content. As the air void content for all sections examined is 8.5 percent or lower, no sections with excessive air voids were considered in the study. Thus, it is difficult to correlate stripping behavior directly with excessive air voids or air void content in general. In addition, previous to the MnDOT study published in 2013 (Wood & Cole, 2013), many state and city/county engineers supposed that there may exist a relationship between (A) a specific bituminous mixture, contractor, geographic location, or year of construction and (B) the likelihood and extent of stripping. Table 12 summarizes data addressing this hypothesis. One limitation of the project was the lack of pavement information from municipalities on the sections considered; much of the information provided lacked specific detail on the mix design, for instance. However, based on the data available to this project, a correlation is not apparent between stripping in chip -sealed pavements and a specific mix, contractor, or paving year. 32