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D \ 04E$0,4yO Chapter 2. Minnesota Department of Transportation a a Cf s '''oP TftP'4.- Chapter 3. 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 DATE: July 17, 2012 SUBJECT: Task 3 memo for LRRB 904 Stripping Under Chip Seal Study This memo will document what was completed in Task 3 of the LRRB Research Project INV. 904 Stripping of Hot -Mix Asphalt Pavements under Chip Seals. Task 3 was to test cores from city streets to test the hypothesis developed in Task 2. The hypothesis states that areas of low density or high air voids in the asphalt pavements are the major contributing factor to stripping of the Hot Mix Asphalt (HMA) after a chip seal has been placed. Numerous streets were reviewed and three (3) cities were picked for study, Brooklyn Center, Eden Prairie and Woodbury. These cities were selected based on a significant amount of streets having stripping issues. Selection of streets to evaluate and the evaluation procedures are described below. First a visual review with City Street Department personnel was conducted. Based on this review, areas were selected for further evaluation. On the streets that had previously received a chip seal, the following methods were used for evaluation. A nuclear density gauge was used to perform a nuclear density test (NDT). The gauge was place on pavement close to the area of stripping ensuring uniform contact from gauge and the street. Two (2) reading were taken at 90° to each other (Figure 1). Then the gauge was placed as close to the stripped area as possible that showed no sign of damage. Two (2) more tests were performed similarly as previously described. This process continued until the complete paving pass had been tested. Then cores were cut at same location as the NDT readings (Figure 2) C-1