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Washington County

Review of suspected premature alligatoring and raveling on chip seals post-2008. Field trip assessment, causes, and testing program details.

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Washington County

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  1. Washington County Chip Seal Program Review Fall, 2011

  2. Meeting Format – 11/17/11 Office (10:00 to 11:00) Problem Description Chip Seal Program Suspected Problem Causes Field Trip (11:00 to 2:30) Dorland/Moreland/Solberger Rds. Lunch Reiling/Chalmers/Wilkesboro Rds. Riedweg/Dober Rds. Wrap up discussion

  3. Problem Description Possible premature alligatoring on chip seals constructed since 2008 (3 years). Apparent premature raveling (loss of top course) in these chip seals. In limited areas, but these problems appear to be more prevalent on relatively new projects.

  4. Moreland Road

  5. Moreland Road

  6. Chip Seal Program Single Shot Bituminous surface treatments over paved or chip seal roads (1x BST) – about 30 miles per year (1x BSTs are not a problem). Three Shot Bituminous Surface Treatments over prepared aggregate base (3x BST) about four miles per year. Also called “gravel road upgrades” or GRUs. 33 miles (~40 roads) have been upgraded, mostly with 3x BSTs since 2004.

  7. Chip Seal Information Oil furnished by Albina Oil. Base and Chip Seal Aggregate furnished by Baker Rock and Westside Rock (2011 only). Construction by Washington County Department of Land Use and Transportation, Operations and Maintenance Division --- “Road Crew”. No formal thickness “design”. We look for a minimum of 6” base rock. Most projects are successful.

  8. Chip Seal Components First shot: 0.5 gal/sy prime coat. HFMS or MC-250 (prior to 2008). ½”-1/4” crushed agg. at 35 lb/sy. Second Shot: HFE 901s at 0.55 gal/sy. ½”-1/4” at 28 lb/sy. Third Shot: HFE 901s at 0.45 gal/sy. 3/8”-10 at 28 lb/sy.

  9. Possible Causes Change from MC-250 to HFMS Base rock too “clean”. Base rock too “dirty”. Too much traffic. Too little base thickness. Isolated drainage issues. Top course of chip seal rock dirty? Improper mix design same size agg. in layers 1 and 2? Combinations? Other issues?

  10. Roads completed since 2004. Roads to be visited on field trip are shaded and bolded.

  11. Testing Program Duval Engineering Lab tests by Carlson Testing Eight roads, four tests per road. Two from good areas, two from distressed areas. 34 total testing locations. Sand patch test to check surface texture. Rut depth measured. --- Continued ---

  12. Testing Program Photo log. 8” core taken, plug retrieved and measured. Extraction test to determine ac% and rock gradation. Thickness measured. Prime coat penetration observed. --- Continued ---

  13. Testing Program Base rock depth measured. Sample retrieved (gradation). Visual characterization of sugrade observed. Subgrade DCP test. Subgrade Atterberg Limits test.

  14. Field Trip Sites

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