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D \4ES0,4yO Chapter 6. Minnesota Department of Transportation a a Oc s<N T1� .g Chapter 7. Memo Office of Materials Office Tel: 651/366-5573 1400 Gervais Avenue, Mail Stop 645 Fax: 651/366-5461 Maplewood, MN 55109 TO: Tom Tesch T.L. DATE: September 20, 2012 SUBJECT: Task 5 for LRRB 904 Stripping Under Chip Seals Background Analysis of the data collected in Task 3 will be discussed and presented in Task 5. It was shown in task 3 that all the tests, permeability, air voids, and density, correlated. The data showed that streets had high variability in density from 7 to 12 percent air voids in areas close to the stripped areas. In the areas with severe stripping cores were not able to be retained for testing. This was due to the cores disintegrating into many pieces after pulling the core from the pavement. Nuclear density testing showed great amount of variability in the mix density from areas of not stripping to areas suffering from stripping. One street had the density varied from 145 lbs/ft3 in areas of the street with no issues to a low of 117.3 lbs/ft3 in areas experiencing stripping. For field evaluation of streets the nuclear density tester is the fastest and easiest to use of method tested. After discuss with experts from around the country it is recommend to not chip seal a street if the variability in density varies more than 6 lbs. per cubic foot as measured with nuclear density tester. Data Figure 1 shows that that when comparing the density to either air voids or lab permeability, the correlation is similar. This indicates density, air voids, and lab permeability are correlated to each other. As density increased and lab permeability and air voids decreased, less stripping was observed.