Narrow Pavement Widening

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Prepared by Kory Keller of Allen Keller Company, this presentation discusses the process and issues involved in widening highway shoulders. Please remember to cite this research if the information you find here is used.

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Narrow Pavement Widening

  1. 1. Narrow widening projects Kory Keller Allen Keller Company
  2. 2. Intro • Ranch Road, and Farm to Market experience. • Parameters • Constructability • Efficiency • Construction Safety
  3. 3. Topics • Safety Slopes • Flex Base vs. HMAC • Aggregate Prime • Widening vs. Rehabilitation
  4. 4. Safety slopes – the enemy • Work that is not gainful to the progress of the project. • Quality Control issues • Permeates Runoff
  5. 5. Slopes (cont) • While safety slopes are an obvious and necessary hazard abatement, the elimination of the hazard is even better.
  6. 6. How can we avoid the safety slope hazard? • Avoid the use of multiple layers in pavement design • Multilayer Example: 6 in flex base, prime, and 2”hmac
  7. 7. How can we avoid the safety slope hazard (cont)? • Consider using a single layer, or “monolithic” approach. • Monolithic example, 6 or 8” of flex base over subgrade, or 4-8’’ of hmac that fills to final surface. • The need for the safety slope is eliminated.
  8. 8. Flex base vs. hot mix • Flex base is considerably cheaper, especially as we move farther away from the hmac plants. • HMAC is seasonal • Unsuitable subgrade risk
  9. 9. Benefits of aggregate prime • Quick and reliable protective cover • Finished base under Traffic • Adheres very well to base course • Low maintenance under traffic in comparison • Protects ride quality on finished base
  10. 10. Benefits of aggregate prime (cont) • Traffic uses the widened road immediately • Cheap base slope protection • All season application
  11. 11. Aggregate prime recommendations • RC-250 with Grade 5 aggregate • 0.2-0.23 g/sy • Grade 5-Grade 6 •dry screened •Non-coated
  12. 12. Widening vs. Rehabilitation • Benefit/Cost Ratio • Labor • Equipment • Project Duration is comparable between widening and Rehabilitation
  13. 13. Widening vs. Rehabilitation • Major components of increase • Cement • extra base • second full width chip seal
  14. 14. RM 336 Real
  15. 15. Completed Project RM 783 Gillespie
  16. 16. Rehabilitation Project US 83 Kerr
  17. 17. Widening RM 336 –Post Agg. Prime
  18. 18. Widening RM 336 –Post Agg. Prime
  19. 19. Widening RM 335 –Before Agg. Prime
  20. 20. Typical Milling Machine
  21. 21. Finishing Base RM335 Real

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