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

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Using cores from a two (2) year old fog seal and the lab permeability (ASTM PS 129-1) test method it was demonstrated that fog seal did not allow water in liquid state to infiltrate the HMA but allowed water in a vapor state to escape. (See Appendix C). Figure 3: Nuclear density tester. Task 4 In Task 4 current methods used by cities to construct their streets was reviewed. These methods were compared to MnDOT's standard specifications for paving. During discussion with agency personnel one fact that relates to density became apparent. Most cities were using ordinary compaction to obtain density. Ordinary compaction, when executed properly should yield good density of the pavement. However, one issue with ordinary compaction is that contractor and agency personnel must ensure that all areas of the pavement receive proper number of rolling passes at proper temperature of asphalt mixture. When streets have variable widths and curves are present it is more difficult to ensure the rolling pattern is consistent throughout asphalt pavement placement. MnDOT recommends using specified density methods. With specified density the agency will take cores randomly from pavement to verify that proper density has been achieved (see Appendix D). Task 5 Analysis of the data collected in Task 3 was discussed and presented in Task 5. Using the different methods outline above, it was shown that all the test methods correlated. The data showed that streets had high variability in density from 7 to 12 percent air voids in areas close stripped areas. In the areas with severe stripping cores were not able to be retained for testing. This was due to the cores breaking into many pieces after pulling the core from the pavement. Nuclear density testing showed great amount of variability in the mix weight per cubic foot from 4