FDR Project Selection and Upfront Testing Tom Scullion TTITREATMENT EMULSION FOAMED ASPHALT CEMENT...
Transcript of FDR Project Selection and Upfront Testing Tom Scullion TTITREATMENT EMULSION FOAMED ASPHALT CEMENT...
FDR Project Selection and Upfront Testing
Tom Scullion TTI
FULL DEPTH RECLAMATION WITH ASPHALT BINDERS
STATE OF THE ART
Lubbock Jan 2019
Overview of Presentation
1. Why Asphalt Treatment
2. Challenges/Opportunities for FDR in Texas1. For TxDOT and Counties
3. Critical steps in FDR Design process
4. Use of NDT in upfront testing
5. Case study on US 84 Lubbock
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Comparative Costs of FDR materials and TreatmentTreatment TxDOT Project Lettings from May 2014 to November 2018
TREATMENT EMULSION FOAMED ASPHALT CEMENT
Districts
AmarilloBeaumont
OdessaSan Angelo
AtlantaLaredo
LubbockSan Antonio
Waco
Districts that have used emulsion & foamed asphalt.
# Projects 15 5 82
$/TON (Material) $507.25 $498.14 $152.25
$/SY (Treatment) $3.99 $4.14 $2.36
Total $/SY $12.23 $9.93 $4.07
Assumptions: Treatment Depth of 8 inches Unit Weight of 125 LBS./CF
238 Gallons of Emulsion per Ton
Total $/SY for Emulsion & Foamed Asphalt include 1% cement. Cement Treatment at 3%
Why Asphalt Treatment?
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• Curing time is less.
• Traffic can be returned onto lane sooner minimizing lane closures.
• Not prone to shrinkage cracking.
• Less susceptible to fatigue damage under heavy loads.
• Flexible to bridge softer and expansive soils.
• Better resistance to moisture prior to sealing.
Texas…
• Opportunities No shortage of candidates
• Inadequate structure for loads
• Inadequate width
Challenges
• Variable pavement structure
• Construction on top of expansive clays
• Often poor existing base materials
• Early opening requirements in Energy Sector
• Need to accelerate Lab designs
• Need updated Specs and Design recommendations
TxDOT Challenges and Opportunities for FDR
Challenges for Counties
Working with Williamson CountyJeff Ivey Point of Contact
2 locations samples 8 inches deep
Dried, Sieve Analysis, PI -determines Job Mix options
Critical Steps in TxDOT’s FDR Process1. Assemble Background information
Coring logs
Maintenance
Typical section
2. Non-destructive testing
Ground Penetrating Radar (GPR)
Falling Weight Deflectometer (FWD)
Determine thickness & strength variability
Determine sampling locations
3. Verify Pavement Structure & Sampling
Auger or milling machine for sampling.
Drill logs for project
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4. Laboratory Mixture Design
Plasticity Index
Moisture-Density Curve
Binder tests (foaming)
Asphalt %, additive %, add rock % and foaming water %
5. Pavement Thickness Design
6. Construction Quality Control
Depth of pulverization
Gradation
Moisture content
Emulsion content
Foaming asphalt properties
7. Construction Quality Assurance – Density
8. Performance Evaluation – FWD and Visual
E. Preparation of the Base Specimens Stabilized with the Emulsion-Cement Mix - CONTINUED
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10. Mix for no more than 60 ± 10 seconds.
11. Place the loose mixture into a bowl.
12. Move the blended specimens into an oven and
cure at 60°C (140°F) for 30 minutes. Do not mix
during curing.
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13. Compact the cured mixtures according to (B).
14. Place the compacted specimens on the porous
stones.
Day 3
Day 4
15. Move the specimens into a climate chamber set
at 60°C (140°F).
16. Cure the specimens in the chamber for 48 hours
(2 days).
17. Remove the specimens from the hot chamber
and cool them at 25°C (77°F) for 24 hours (1 day),
but not more than 48 hours (2 days).
Upfront Site Investigation
PI Soil Maps
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Step 2 NDT Air-Coupled GPR (use visual + GPR to select sampling locations)
• Integrated Video and FWD
• Data collected at highway speed (60 mph)
• Effective depth of penetration 20 ins
• TxDOT has 5 available units
• Measures layer thickness and locate subsurface defects and section breaks
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Bottom HMA
Bottom base
FM 1996 Waco
Step 2 in the FDR ProcessFalling Weight Deflectometer
(FWD)
Subgrade Modulus determination
Step 3 in the FDR Process
Sampling Equipment
• Use GPR/visual information to determine sampling locations.
GradallMilling AttachmentAuger
Critical Steps in the FDR ProcessCoring Log
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CENTER/BETWEEN WHEELPATHS OUTSIDE WHEELPATHSEVERE RUTTING, ALLIGATOR & LONGITUDINAL CRACKING
Why Upfront TestingTxDOT’s 1st foamed asphalt project (2000) < 1 year old
Recycled 10 inches deep - Problem: locally only 7 inches of pavement over black clay
374+2439
382 +2439
383+4488
Section SB 1
SB 2
SB 3
SB4
NB 1
NB 2
Is SB 2/3 FDR candidates?
383+ 5254
Corridor Study on US 84
SB 2 Problem Section7.7 miles section
2 Inches HMA surfacing6 inches Type B or ASB11 – 12 inches “reworked base”Subgrade (sand to clay with sulfates)
50 full depth patches SB OL Each patch 12 to 14 inches deep Multiple full depth patches inside lane
Condition• Lots of maintenance on-going• 2 inch mill/fill just completed by
TxDOT forces• Localized failures still exist
Start SB 2
End SB 2
patch Patch 12 – 14”BottomHMA 8-9”
GPR dataExamples of full depth patches
surface
Current failures - sample recovery
Typical failure
Recent 2” Mill/Fill
Sampling Base and Surface
South Bound Drill LogsSite HMA Base (PI) Subgrade (PI) Sulfates
(ppm)Comments
1 7.5” 12” Red Clay Top 2 inch Stripped over crack
1A 7.5” 8” (9) Red Clay (39) 480 Top 2 inch Stripped over crack
2 7.0” 12” (25) Grey Clay (33) 950 Poor base (High PI)
3 8.5” 11” Silty Sand Poor base – FDR Sampling location
3A 8.0” 12” (15) Silty Sand (15) 1310
4 3” 17” (9) Red Clay (21) 27000 Very Thin HMA cracked
Low QualityReworked Base
Cause of Problem
• Water entering low quality base material thru cracks in the HMA layer
• 8 inches of HMA reasonable quality
• “Reworked Base” PI ranges from 15 to 25
• FDR options to address problem layer and structural needs– FDR on base materials
– CIR on salvaged HMA
Lime Treatment of Existing base3% lime works fine
How good is the US 84 RAP(Active/Inactive Binder)
US 84 judged to be excellent RAP attains passing wet strength with no treatmentLocation sampled had a new 2 inch mill/fill
IDT on 100% RAP samplesEverything except Hamburg looks good SS 3254
Because of success in Amarillo recommend 1.5% lime plus either emulsion or foam
Proposed FPS 21 Pavement Design
Conclusions
• Upfront testing is important to
– Select sampling locations
– Hopefully avoid surprises in construction
– Part of the structural evaluation to determine if FDR or CIR is an alternative for this highway
– To determine what thickness of surfacing is required to handle traffic loads