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Plant Mix Overview

Plant Mix Overview

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Plant Mix Overview

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  1. Plant Mix Overview MDT Training Conference Billings, Montana March 1 & 2, 2006 Presented By: Matt Strizich and Danny Hood

  2. Recent Plant Mix Use

  3. Volumetrics Incentives • 1.45 million or 2.85% in 2005 • 0.48 million or 3.16% so far in 2006 • Percentage of total spent on PMS that year

  4. Ride Specification Incentives • 0.39% in 2002 • 1.51% in 2003 • 0.9% +/- from 2004-2006 • Percentage of total spent on PMS that year

  5. Compaction Statistics

  6. Compaction Issues • Compaction incentives were 1.04% in 2003 and 1.20% in 2004 • Dropped to 0.34% in 2005 • Have a net disincentive of 0.22% so far in 2006

  7. Quick Notes • Volumetrics and the Ride Specification are not included on all projects • All end-result specifications

  8. Contractors are Earning it! • MDT is paying 3-5% of PMS costs in incentives • Plant production has been slowed • Seeing quality compete with production

  9. Purpose • Present potential future changes • Provide reasoning behind changes • Share information from last year • Provide the opportunity to ask questions

  10. Topics • Grade S & Grade D Commercial Specification Revisions • New ½” Grade S Policy • Ride Specification Revisions • Compaction Issues in 2005 • Aggregate Surface Treatment Experiment

  11. MDT Staff • Construction Reviewers • Project Staff • Internal Audit

  12. Contractors • Montana Contractors Association (MCA) • Non-Uniformity Complaints • Claims

  13. Specification Change Process • All specification revisions go through the Specification Section • Dan Smith and Ryan Antonovich • Defined process • Standards Committee coming soon

  14. Change Process • Ensures thorough review • Reviewed by MDT staff and contractors

  15. Plant Mix Specifications Grade S and Grade D Commercial

  16. Grade S Volumetrics Non-Volumetrics Grade D Commercial Tested Non-Tested Grades of Plant Mix

  17. Why two versions? • Contract administration • Quality of the same grades of mix should be equal. • Testing and frequency of testing varies

  18. Grade S • Completely revised mix • Grade S has been successful • Moved to gyratory compactors • Bob Weber and Scott Barnes deserve the credit

  19. Volumetrics • Volumetrics is how MDT administers and controls the plant mix quality • True end result specification • Successfully encourages contracts to control their operations • Want quality to be able to compete with production

  20. Grade D Commercial • Relatively new specification • Always used on “smaller projects” • Bill Fogarty leading the committee

  21. Grade B • Use for bike paths or other features not subject to heavy loading • Consider using Grade D or S with chip seals instead

  22. Grade C • No longer needed • Grade D Commercial should be used instead

  23. Change Process • Plan to review specifications yearly • Will continue to see the same issues if they are not identified • Anyone can initiate change • People doing the work need to identify the issues • MDT Project staff • Contractors • Reviewers

  24. Grade S Changes • Changes are minimal • Changes are the same for volumetrics and non-volumetrics versions

  25. Mix Designs • 50 Gyration mixes have been eliminated • SHRP recommendation for low volume roads • Created issues with meeting Hamburg testing requirements

  26. Release Agents – Specification • a)Trucks. Remove trucks from service that leak fluids. When directed, cover each load with canvas or other approved material to protect the mix at Contractor expense. Do not use Diesel fuel as a truck bed release agent. Use a commercially manufactured release agent approved by the Project Manager.

  27. Release Agents - Specification • b)Rollers. Furnish and use rollers that compact the plant mix to the specified density. Remove rollers that crush the paving aggregates or otherwise damage the plant mix and replace the damaged plant mix at contractor expense. • Cleaning Agents. Do not use diesel fuel as a cleaning agent or as a release agent for any paving equipment or operations. Use a commercially manufactured release agent approved by the Project Manager.

  28. Release Agents - Justification • Expands the existing restriction on diesel fuel to all equipment • Need to be uniform in our enforcement. • Contractors will include additional cost in bids • Will eliminate having the issue every time paving starts

  29. Release Agents - Justification • Plant Mix quality • Employee safety • Environmental concerns

  30. Tack • The cost of SS-1 will be incidental to the cost of Plant Mix Surfacing • Includes tack between lifts of paving and for sealing rumble strips • Tack is still required in all instances it was previously used

  31. Tack • SS-1 will still be a pay item for some uses • Aggregate surface treatment • Fog sealing • Reasons for change • The number of lifts is no longer specified • Low cost item

  32. Grade D Commercial • Mostly Clarifications • Extensive revisions last year • Previously relied only on compaction to control • Not enough control so 5% penalties on specified properties was added

  33. Grade D Commercial • Wording change • Material. Provide Grade D Commercial Plant Mix Bituminous Surfacing with the specified asphalt binder, 1.4% hydrated lime, and meeting Table 701-15A requirements. Use fillers or additives as necessary.

  34. Grade D Commercial • Clarification • c) Sampling. Sample the PGAB meeting subsection 402.03.2 (B). A sample is two one-pint (two 500 ml) containers of PGAB. Sample fillers, hydrated lime, additives, aggregate treatment and tack in accordance with MT-601.

  35. Grade D Commercial • Revised target air voids • Percent Air Voids: changed from 3-5 to 2-4 • Do not want drier mixes • Cost of oil is included in the Grade D Commercial bid item

  36. Grade D Commercial • Reweighing of vehicles is no longer mandatory • It should still be done in most cases • The Project Manager may randomly designate the re-weighing of loaded vehicles.

  37. Grade D Commercial • Reduced the “F” factor from 12 to 6 • a)Acceptance. Rescind Subsection 401.03.12 (E) and replace with the following: Plant mix surfacing is evaluated for density on a lot-by-lot basis under Subsection105.03.2, except as noted in Subsection 401.03.12(B). Change the “F” factor for the Compaction element in Table 105-2 Table of Price Reduction Factors from 12 to 6 for plant mix furnished under this provision.

  38. “F” Factor Change • Compaction is no longer the only measure for controlling quality • Want to be consistent with other mixes • Inflated prices due to haul • Too much risk for Contractors

  39. Grade D Commercial • Wording clarification • A 5 percent price reduction (15% maximum), in the unit bid price for PMS Grade D Commercial will be applied for each test not meeting the Mix Design Stability, Flow, Percent Air Voids, Asphalt Binder Properties, Gradation, or Asphalt content specified. Price reductions will be assessed on the quantity of material represented by each failing sample. The quantity of material represented by each sample is the total tons of material produced divided by the total number of samples representing the material.

  40. Grade D Commercial • The quantity of material represented by each sample is the total tons of material produced divided by the total number of samples representing the material. • Changed to help keep administration uniform • Fairer to the contractor

  41. Grade D Commercial – Non Tested • Many of the same changes as the tested version • Price reductions are only assessed for obviously defective material • Added the following: Provide the Project Manager density testing results upon request.

  42. Contract Administration – Tied Projects • Issue has been identified • Materials working with construction to develop guidance

  43. ½” Grade S Policy

  44. Why? • Compaction Concerns • Reduced lift thicknesses • Lower overall cost

  45. October 2003 Policy • ½” Required for all lifts less than 60 mm • Introduced in response to Grade S compaction concerns • Followed SHRP recommendations

  46. Revised Policy – April 2005 • Limited use of ½” Grade S to low volume roads • Reduced the overall use.

  47. January 2006 Revision • Construction Memo • Requires the use of ¾” PMS whenever 0.15 ft or greater is required • Requires ½” Grade S only be used for overlays • Allows reduced overlay depths if ½” is used

  48. Additional Requirements • ½” Grade S can only be used if: • Ave. Rut = 0.20 inches or less • Ave Ride = 80 in/mile or less • An isolation lift is required • Surfacing Design must approve

  49. Implementation • Surfacing Design will review existing design projects and make recommendations • Projects will not be changed from ¾” to ½” Grade S • Change orders will be considered – Should not be “no cost”

  50. ½” Gr. S is more difficult to compact ½” Gr. S is more expensive ½” Gr. S is equal to or better than ¾” structurally ½” Facts