U.S. National Overview Cold-In Place- Recycling. Laramie, Wyoming 18 th July 2013

Transcription

1 U.S. National Overview Cold-In Place- Recycling Laramie, Wyoming 18 th July 2013

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3 Why recycle? Correct pavement defects Increase structural capacity Geometry Limited elevation rise or limited width Reuse valuable resources Economics Reduce environmental impact

4 FHWA Recycled Materials Policy Recycling and reuse can offer engineering, economic and environmental benefits. Recycled materials should get first consideration in materials selection. Determination of the use of recycled materials should include an initial review of engineering and environmental suitability. An assessment of economic benefits should follow in the selection process. Restrictions that prohibit the use of recycled materials without technical basis should be removed from specifications.

5 What is in-place recycling? A pavement rehabilitation technique that reuses existing materials in a cost-effective way.

6 What is in-place recycling? Cold In-Situ Recycling Base Stabilisation Full Depth Reclamation 350mm 350mm

7 CIR Cross Section

8 CIR Cold in-place recycling with HFMS-2/CMS- 2/CSS-1 In place 3-5 as a train, partial depth (stay within asphalt layer) 4 typical Type 1 with crusher Type 2 no crusher Copyright - Colas Solutions, 2011

9 Typical Pavement Deterioration and preservation or treatment method Condition Excellent Good Fair Poor Very poor Failed Fog seal Chip seal Micro surfacing Thin overlay / HIR Ultra-thin bonded Mill & fill or HIR Cold in-place recycle Full depth reclamation Reconstruct Time, years

10 Pavement Preservation HIR CIR FDR Time / Traffic Loading

11 Condition Survey Functional Distress Surface Distress HIR Core or Depth Check Determine Cause of Pavement Distress Cracking >2 CIR and Wearing Surface FWD on Project with Questionable Structural Section Structural Distress FDR and Overlay

12 Candidate?

13 Candidate?

14 Candidate?

15 Typical CIR Candidate Asphalt pavement with good drainage with side ditches or an internal drainage structure 4 inches or greater asphalt pavement over aggregate base or stabilized base 4 inches or greater asphalt pavement over PCC Very worn asphalt pavement with cracks not going through entire asphalt layer (or low severity at bottom) Asphalt pavement with no signs of rutting or fatigue cracking due to subgrade or aggregate base issues

16 CIR Definition Cold in-place recycling (CIR) is the on-site recycling process with a typical treatment depth of 3 to 5 inches, using a train of equipment (tanker trucks, milling machines, crushing and screening units, mixers, a paver, and rollers), an additive or combination of additives (asphalt emulsions, lime, fly ash, cement), generating and re-using 100% RAP, with the resulting recycled pavement usually opened to traffic at the end of the work day.

17 Type 1 Type 2 ADD AGGREGATE 4 MILLING MACHINE 10 CROSS SECTIONAL DIAGRAM TYPE 1 & TYPE 2 RECYCLE PROCESS

18 CIR TRAIN LIME SLURRY TANK MILLING MACHINE CRUSHER PUG MILL EMULSION TANK PAVER

19 Recycling Train Type 1 (with pugmill and paver) Courtesy Center for Transportation Research and Education, June 2007, Iowa State University Can be placed on ground or directly in paver hopper

20 Recycling Train Type 2 (with mix paver)

21 UNFINISHED SIDE AS COMPARISON COMPLETED RECYCLED LAYER

22 Cold-In-Place Recycling

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24 CIR Alternatives Overlay Mill and fill Hot in-place recycling Not a real alternative due to typical ¾ 2 depth. Some contractors perform 2.5 depth.

25 Is pre-milling needed (curb and gutter, room for overlay, etc.)? Existence of manholes and obstructions Recovered core depth and location of cores Base and subgrade types and depth Drainage concerns Existence of shoulders / type / to be recycled? Cross slope existing and new Client expectations Information needed

26 Mix Design Testing Depends on specification requirements and job requirements Some states require volumetric design only (i.e. PA) Some states require target gradation (i.e. NY) Some states require Superpave gyratory compaction and strength / performance testing (i.e. IL, KS)

27 Various mix design tests CIR CIR Grinder / crusher Extraction Mixer Superpave gyratory compactor or Marshall Raveling test Marshall or ITS Retained strength Thermal cracking Purpose Simulate milling AC content and gradation Simulate mixing Simulate long-term density Adequate setting Long-term strength Key performance indicator Non-load cracking

28 Sample Cores

29 Mix Design Kansas DOT 4 in (100 mm) specimens shall be prepared in a Superpave Gyratory compactor. The mixture should meet the following criteria at the selected design asphalt emulsion content: Property Compaction effort, Superpave Gyratory Compactor Density, KT-15 Gradation for Design Millings, KT-3 Marshall stability *, KT-14, 104o F (40o C) Retained stability based on cured stability ** Thermal cracking, AASHTO TP9-96, Modified in KT-60 Raveling Test, Ambient, KT-61 Criteria Refer to KT-58 Report Report 5.56 kn, min. (1,250 lbs) 70 % min. See note in KT-60 2 % max. * Cured stability tested on compacted specimens after 140 F (60 C) curing to constant mass. ** Vacuum sat. of 55 to 75 percent, water bath 77 F (25 23 hours, last hour at 104 F (40 C) water bath.

30 Mix Design - CDOT

31 Longevity Factors CIR with surface treatment 6 to 8 years CIR with HMA treatment 12 to 20 years

32 Gradation / material changes CIR Gradation in field can be different than design gradation, resulting in a needed emulsion content change Gradation on project will change depending on machine speed and temperature Too coarse raveling Could measure using 12 diameter sieves down to No. 30 FDR Most common problems are RAP / base blends that are different than mix design impact on coating and needed emulsion content While good field sampling should obtain materials representative of field conditions, not every problem area (or thin bituminous, etc.) will be identified

33 Barriers to increased use of in-place recycling Lack of mix design (agency response) Unsuccessful experiences Lack of experienced contractors Lack of agency experience Lack of engineering design Competing industries Lack of project selection criteria Lack of specifications Source: NCHRP Synthesis 421, Table 40

34 What comes first? Agencies new to CIR / FDR want local contractors existing contractors will only travel so far Potential contractors for CIR would invest in equipment if there was continuous work

35 Barriers from 2012 Western States Recycling Workshop CA No real challenges listed for implementation NV No real barriers, but turnover in the DOT has probably led to more mill and fill WA Limited PP dollars, CIR limited to worst roads (there aren t many), high traffic volumes, fabric ID Doing FDR when could be doing CIR due to familiarity with FDR; need to understand project selection better for CIR MT CIR failures from years ago still carries over to doing little of it today

36 Barriers from 2012 Western States Recycling Workshop UT Many CIR projects on interstates with success; need better QA and way for DOT lab verification CO No barriers AZ No barriers discussed; want end-result spec AK No barriers discussed NE Subs and primes working together / scheduling; they do some work, but mill and fill with 50% RAP is cost competitive TX Alternate bids with HMA makes it tough to do CIR

37 Progress is being made ARRA is addressing the barriers A new BARM with specific project selection criteria, best practices for construction, and other information (2014) Mix design procedures that work well will be published on website NCHRP 9-51 is incorporating FDR and CIR into the MEPDG pavement design program Colas is participating

38 Project selection Distresses not excessive for the treatment Composite pavement - CIR Summary Drainage! Can t be over-emphasized. Investigation and Sampling Design samples must represent the width and length of the project Design samples must represent material changes in the pavement structure Make note of stripped or delaminated layers. Beware of treatment depth or process that leaves these layers in place. Clay or weak subgrades and CIR train support

39 Recycling works and has a proven track record Reduces costs and time 25-33% or more savings ½ to 1/3 the time of reconstruction Conserves energy 50-70% reduction Summary Conserves resources by using existing, in-place materials (often high quality) Eco-friendly by reducing the use of fossil fuels

40 GREEN?

41 Valuable resources if more information is needed ARRA Basic Asphalt Recycling Manual Recycling and Reclamation of Asphalt Pavements Using In-Place Methods, NCHRP Synthesis 421, 2011 Cold In-Place Recycling and Full Depth Recycling with Asphalt Products, Illinois Center for Transportation, Series No , March 2009 Cold In-Place Recycling in New York State, Contract 6764F-2, New York State DOT, July 2010 Recycling seminars External Resources

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43 Discussion or Questions? (easy questions only!) Iain Jack Heartland Asphalt Materials