Reclamation Guidelines

Transcription

1 Reclamation Guidelines MAAPT 63 rd Asphalt Conference December 7, 2016 Terry Beaudry MnDOT Grading Base, Recycling, and Aggregate Engineer

2 Outline 2 Design and Preliminary Work Construction Production and Inspection Common Problems Cold In Place Recycling (CIR) Cold Central Plant Recycling (CCPR) Stabilized Full Depth Reclamation (SFDR) Full Depth Reclamation (FDR) Hot In Place Recycling (HIR)

3 Preliminary Work - All 3 Assess Roadway Conditions Core every 1000 for depth & Condition of HMA, Base, and Subgrade Assess gradation, depth, FAA crushing percentages of HMA (burn) DCP after core removed, then auger for base sample Perform Ground Penetrating Radar (GPR) to supplement coring Assess whether there are weak spots that you want to repair, preferably with lime/cement stabilization, fabric may also be used Perform assessment and a mix design. Designs for CIR, CCPR, and SFDR are in Grading and Base Manual Assess for what would be best project fix Need to meet design criteria MnPave, GE, SN, or other.

4 Cores - Note Height and Gradation 4

5 CIR Design and Preliminary Work 5 Cold In Place Recycling Want at least 1-2 HMA to remain in place. Rule of Thumb want at least 4-5 in situ HMA. Roads that are predominately structurally sound. Paver Laid so close to one lift of hot mix for ride quality. Make sure you do not over-mill, want rock and crushing in final product, or need to add rock, cement and/or lime to mix design Consider as alternative on second or third OL as successive overlays tend not to last as long as first ones Note that you can t fix profile, i.e. no excess material. May be used for BOC, Iowa has had great success with crack suppression Consider where there are no or few areas where additional structure is needed If strength needed in isolated spots, mill off HMA and remove base, then fix by cement treating subgrade then bringing back as CCPR 20 year design life Economically good alternative to 3 4 overlay as reflective cracking is alleviated

6 CCPR Design and Preliminary Work 6 Cold Central Plant Recycling Both CIR and CCPR produce the same product. One should only choose CCPR where the project dictates that CIR cannot be used because of project constraints. For most central plant cold mix (CCPR) projects the asphalt is milled from the project and stockpiled on site for CCPR. A Cold in place mixing device (may use the same mixer as used for CIR projects), processes the mix and then the mix is hauled back, placed, and compacted.

7 CCPR (cont.) 7 Cold Central Plant Mix CCPR mix is produced by mixing RAP with an emulsion or foaming bitumen. If cement is required by mix design, place immediately after mixing Since there is extra handling, it is more expensive than CIR

8 Uses for CCPR I believe that two good uses of CCPR would be the following: Best: Where you have a full depth bituminous section over very little or no base over a weak subgrade. Remove all but 2 of HMA, stabilize with subgrade and lime or cement, and compact. Bring back 4-8 of the CCPR mix (4 maximum lifts), place and compact. So some typical MnDOT Full Depth HMA roads with 10 HMA: Mill 8 Stabilize 6 12 of subgrade (leave 2 HMA for a platform and incorporation into the subgrade) Bring Back 1 to 2 four inch max lifts of CCPR Place new HMA on top Good alternative to white-topping: fixes weak subgrade, therefore longer life is anticipated May be less expensive (perform economic analysis) No grade raise 100% in place recyclable next time road is repaired 8

9 Uses for CCPR (continued) 9 Good Use: On shoulders where either the width or the Structure underneath the HMA is not adequate to support a CIR train. Mill the shoulder, haul the milling to a central site on the project, process, then bring back CCPR mix, place and compact. Competitive if replacing 1.5 of HMA: i.e. 3 CCPR plus 1.5 HMA is approximately equal to 3 HMA on shoulder.

10 SFDR Design and Preliminary Work 10 Use SFDR where you need to beef up base over a large portion of project, or HMA is too thin for CIR (less than 4 ), otherwise use CIR or FDR Design so that you only go into base 1 2 use your depth checks, less $ more uniform Make sure you do not over-mill, want rock and crushing in final product, or need to add cement and or lime to mix design Be willing to repair week areas if needed. Again - Consider starting on second or third OL where added strength in the base is needed as successive overlays tend not to last as long as first ones Consider isolated areas where additional structure is not needed If needed in isolated spots, fix by cement treating subgrade then bringing back as Cold Mix 20 year design life Economically good alternative to 3 4 overlay Reflective cracking is alleviated

11 SFDR Design & Preliminary Work (cont.) 11 SFDR Full Depth Reclamation Blade Laid SFDR two passes pulverize then inject, FDR one pass SFDR higher oil demand than CIR SFDR oil demand depends on amount of base incorporated

12 CIR versus SFDR versus FDR Perform an economic analysis for CIR, FDR, & SFDR to determine total cost which depends upon how much HMA is needed for each design.

13 Design for Depth of SFDR or FDR Plan Material Removed after Reclamation 13 Photo used from Ruston Paving Company website

14 HIR Design and Preliminary Work 14 Hot In Place Recycling Where Used: Raveling of HMA Treats the top 2-3 only Has been used in some for Minnesota counties and cities, but not for State work Do not have a special provision, within the Bituminous Unit

15 Economics 15 Assumptions: Oil at $45/Barrel PG graded foaming oil at $385/ton (Metro short haul), and adequate rock and crushing in mix design HMA at $60/ton = $3.25/sy inch CIR 2% new oil at 4 = $2 + $1.70 = $3.70/sy = $0.925/sy inch 90/10 HMA/Base 2.25% at 6 = $4.85/sy = $0.80/sy inch 50/50 HMA/Base 3.25% at 6 = $6.15/sy = $$1.025/sy inch Overlay year design life CIR/SFDR 20+ year design life (with low initial maintenance)

16 TCRACKH, count/km Iowa Field Performance 70 Average High Severity Transverse Cracking 10 Year Span (3-4 inches HMA Surface) HMA/PCC HMA/HMA HMA/CIP/PCC HMA/CIP/HMA HMA/PCC (MILLED) HMA/HMA (MILLED) Cumulative Trucks, millions

17 Production with all Stabilized 17 Have Preconstruction Meeting Review Weather Requirements Review Equipment requirements Review Depth of Reclamation Review Maximum Size Requirements Review QC/QA checks Take in place moisture before stabilizing FDR, want to be close to optimum moisture, the emulsion or foamed asphalt counts as extra moisture Compaction will be tested by DCP unstabilized or Nuke Gauge for stabilized

18 QC/QA Tests 18 Gradation Maximum Size Requirements Depth Checks Ball Test Foaming Tests Calibration area for density check with nuke gauge Yield Checks Forms and procedures are in the Grading and Manual and website

19 Measuring Grinding Depth 19 A. General Measuring grinding depth in the field is a method of determining the grindinbg depth of HMA and base for (S)FDR and CIR B. Equipment Tape measure, Straight Edge, and Shovel C. Procedure 1. Always wear the proper safety equipment and never stand close to a reclaimer while it is in motion, wait until it is a safe distance away before measuring. 2. Use a shovel to reach the bottom of the reclaim layer, use the adjacent bituminous pavement as a guide. 3. Place the straight edge on the bituminous pavement and the tape measure on the bottom of the reclamation cut and measure the cut depth the nearest 0.5-inch. Measure the cut depth on both sides. Measure both HMA and Base against a non reclaimed HMA.

20 Ball Test Test to see if you can form a ball (if not mix may be too lean) If emulsion is used, let it harden for a half hour, foam test right away, break open with fingers: Should/may flex slightly look if uniform no blobs of oil.

21 Measuring Expansion Ratio & Half-Life of Foamed Asphalt in the Field 21 Figure 28 Measuring Expansion Ratio for Foamed Asphalt NOTE: BAD SAFETY PRACTCE. WEAR GLOVES!

22 Problems FDR and SFDR: Chunks 22

23 Problems SFDR & CIR 23 Material Sticking to Tires

24 Other Problems 24 Incorrect or poor Equipment to reclaim or Compact Teeth Too Dull Reclaiming too fast - chunks Milling too Deep No Rock left in reclaim Material Check Cores and GPR beforehand Reclaiming too Deep Either going into the subgrade or little base to compact against Be aware of 50/50 blend thought process in design May not have structure or adequate rock or going into subgrade For SFDR higher oil demand, HMA 2% oil, Base 4.5% oil demand

25 MnDOT Inspectors Guide For FDR and SFDR On Grading and Base Website Eleven Pages Quick Read Preliminary Responsibilities Coring, GPR, & DCP Choosing Method Mix Design Equipment Requirements Weather Pre-meeting with Contractor Inspector Responsibilities Field Tests Depth Checks and Gradation Ball and Tire Test Compaction Tests Foaming Tests Common Problems 25