Initiatives: PWT, Local Acceptance, and Ignition Furnace Correction Factors • Effort to address & combine issues important to FHWA, Department & Industry • This was presented at the 53rd Annual PAPA Conference, December 12, 2012.
Our 2013 PWL Pilot Project: Group 2-13-ST9 Paving ProjectDistrict 2-0 Juniata, Mifflin (and Snyder) Counties
Project Facts: • Description:The description and location of the project is as follows: For the improvement of certain sections of STATE HIGHWAY in JUNIATA, MIFFLIN, and SNYDER COUNTIES, VARIOUS TOWNSHIPS AND BOROUGHS, Commonwealth of Pennsylvania, GROUP 2-13-ST9. For the improvement to (5) total State Routes in Juniata, Mifflin, and Snyder Counties having a combined construction length of approximately 56,615 feet, (10.7 miles); involving various combinations of milling, bridge deck repair, scratch and resurfacing, using various Superpave Asphalt Mixture Designs or Warm Mix Asphalt for the binder and wearing courses, various pavement markings, and miscellaneous construction as indicated on the approved drawings. • Three different State Routes were to receive “mill/fill, scratch (65 lb.) and resurface (165 lb.) ” operation. • The 9.5mm wearing was the only material tested under the Special 24 page Section 409 attached to the project for PWL testing. No Shuttle-buggy used or required.
Project Facts: • Questions and Responses: • Question 1: Why is the option for Local Acceptance testing not provided for use in this project in the attached Section 409, to go along with the PWL/PWT? • Response: The District has committed to pilot the PWL- LTS specification on this project and the PWL-LA specification on a different project. • Question 2: Which materials (and sites) will be paid for based on Table J of the Special 409 section attached to this package? • Response: The specification will be used for all sites on the project and Table J will be utilized when sites are accepted by lot acceptance. • Question 3: Will LTS determine correction factors for their ignition ovens of the producers mixture(s)? • Response: Bid as presented in the specifications.
Concerns and Variables: Results (pay) for mix comes from what is…was in the box, Correction factors…Our Gilson ovens vs. LTS’ ovens AASHTO T 308-10 states: CORRECTION FACTORS A1. ASPHALT BINDER AND AGGREGATE A1.1 Asphalt binder content results may be affected by the type of aggregate in the mixture and the ignition furnace. Therefore, asphalt binder and aggregate correction factors must be established by testing a set of correction specimens for each job mix formula (JMF) mix design. Correction factor(s) must be determined before any acceptance testing is completed and repeated each time a change in the mix ingredients or design occurs. Any changes greater than 5 percent in stockpiled aggregate proportions should require a new correction factor. A1.1.1 Asphalt binder correction factor—Certain aggregate types may result in unusually high correction factors (greater than 1.0 percent). Such mixes should be corrected and tested at a lower temperature as described below. Each ignition furnace will have its own unique asphalt binder correction factor determined in the location where testing will be performed. A1.1.2 Aggregate correction factor—Due to potential aggregate breakdown during the ignition process, an aggregate correction factor will be determined for each ignition furnace in the location where testing will be performed when the following conditions occur: aggregates that have a proven history of excessive breakdown or aggregates from an unknown source.
Concerns and Variables: Real or Imagined?
Results: 102, 94 and 88% pay. SR 35 = 2,427 tons placed SR 75 = 2,434.32 tons placed SR 305 = 2,594.12 tons placed (No Density Cores) All would have been 100% pay under Normal Specification.
SR 35 = 2,427 tons placed SR 75 = 2,434.32 tons placed SR 305 = 2,594.12 tons placed (No Density Cores)
Is this fair and balanced? • Yes – a bonus can be achieved • Yes – a penalty can be achieved • If “Local Acceptance Testing” is not used – what about appropriate Correction Factors? • Will this Spec be used for appropriate projects/SR’s? • Will it be applied to all size mixes…
Surely, it’s not as AC DC sang… …is it?
Grannas Bros. Stone & Asphalt Blair County SR 164 MC 7 PWT Pilot Project, District 9-0
Blue Knob MC Project Details • $663,883 Low bid amount of contract • 2.6 mile resurfacing contract • Minor 25 mm shoulder upgrade and base repair • 120 lbs per sy of 9.5 MM leveling course • 4358 ton of 9.5 MM Wearing Course, <.3 ESALS, PG 64-22, SRL M @ 180 lbs per sy • Paved last week of Sept & 1st week of October
SURPRISE! at Pre-Job Conference Now I know why we were the LOW bidder
Percent Within Tolerance(PWT) • Pilot project using a pure PWT spec • Payment factors for four criteria • AC Content • #200 Sieve • Primary Control Screen (PCS) • Density • Each pay factor evaluated statistically for spec limits • Up to 4% bonus available to contractor • Less “Harsh” penalty structure – Eases R&R’s • Samples tested at LTS • Directive from FHWA to move in this direction PennDOT 9-0 Construction Unit
Percent Within Tolerance(PWT) • So, how it went… • Lot #1, 25 mm Base (Info only) • Incentive = N/A (Would have been a 2% Bonus if paid) • Lot #2, 9.5 mm Wearing • Incentive = 1% Bonus • Lot #3, 9.5 mm Wearing • Incentive = 4% Bonus • Total Bonus received $5,565 PennDOT 9-0 Construction Unit
1st Lot of Wearing—1% Bonus • Supplier GRB07B41- JMF 020 • Mix Size 9.5mm • # Sublots5 #8 #200 AC Density • Design 36 5.2 5.6 159.3 • AVG. 34 5.3 5.4 151.2 • S.D. 1.2 0.39 0.21 1.23 • PWT 100 100 82 100 • Pay Factor 104.00 104.00 94.00 104.00 • Payment 101
2nd Lot of Wearing—4% Bonus • SupplierGRB07B41 – JMF 20 • Mix Size 9.5mm • # Sublots4 #8 #200 AC Density • Design 36 5.2 5.6 159.9 • AVG. 35 5.3 5.5 152.3 • S.D. 0.8 0.41 0.19 1.10 • PWT 100 100 100 100 • Pay Factor 104.00 104.00 104.00 104.00 • Payment 104
OUR PLAN OF ACTION: • Met with plant, lab tech, supt, paving foreman, and nuclear tech to discuss options & get ideas • FIELD • Selected crew based on who takes box samples the best • Paved consistent speed to aid in compaction • PLANT & LAB: • Pre-processed RAP to get consistent AC content • Had aggregate stockpiles dedicated for this job
WHAT WE LEARNED: • Local acceptance is a must for PWT • Our biggest fear was correction factors at MTD • Were we good, or were we lucky? • One job doesn’t tell the whole story • Bad things happen to good people
New Enterprise Stone & Lime’s Pilot ProjectECMS #91100 District 2Group 2-13-ST1 • Site 11 SR 0144 Clinton County Mix: 9.5mm “G” 50N (58-28) Four- 2500 ton lots
PWT is Percent within Tolerance • Changes include: • Any 1 individual core under 92% or over 97% can give you a penalty if the majority of the cores are at the upper or lower limit! • Tighter tolerance on the #200 sieve • Addition of a “primary control sieve” or PCS • These changes ALONE are tough enough, but adding a different pay scale takes it to a whole new level! • Need to pilot this for a another year for process improvement and risk management to the industry
QUESTION • Is the job a good candidate?? • Are you sure? • Last chance to say NO • Look at ours!
Thank GOD there wasn’t a joint-density spec. on this job too, however this crew did an excellent job on it.
Pro’s and Con’s • PRO’S • Bonus up to 4%, only 2% if using optimum roller pattern • R&R is 70% vs. 50% • Quality pavements • CON’S • Lack of research to impact paving industry • Less chance for 100% PAY • Most plants WILL have to slow down (production) • PCS is added and #200 sieve tolerance tightened • All Drum plants will have to be even more cautious on raw aggregate stockpiles (PCS)
REALITY: • Lot 1-Density=88.75%, AC=101.6%, #200=104%, PCS=104% • PAY 96% • Lot 2-Density=101.2%, AC=83.5%, #200=104%, PCS=97% • PAY 96% • Lot 3-Density=95.5%, AC=104%, #200=104%, PCS=104% • PAY 100% • Lot 4-Density=80.5%, AC=104%, #200=102.4%, PCS=104% • PAY 92% • PAYMENT IF DONE CURRENT METHOD…………100%
Acknowledgment: • Randy Strait, Chief QC Plant technician • Chuck Verbonitz, Paving Superintendant • Cheryl Davis, Compaction/Nuclear Technician • Bob Flood, Area Supervisor/Photographer