Hans Ho: Pavement maintenance challenges and opportunities
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Pavement Preservation
CALIFORNIA ASPHALT PAVEMENT ASSOCIATIONFALL ASPHALT PAVEMENT
CONFERENCESACRAMENTO, CA
October 29 – 30, 2014
Hans Ho, PhDTechnical Director
(Retired)
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Sum of all activities to provide and maintain serviceable roadways
Includes
Corrective & Preventive Maintenance
Minor rehabilitation
Does not include
Reactive maintenance
Major rehabilitation or reconstruction
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Cost effectiveness Energy savings Reduced emissions Reduced user costs Life extension User satisfaction Safety
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Right Treatment
Right Pavement
Right Time
“
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How do I get the decision makers to understand that “worst first” does not work?
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Pavement Preservation - Concept
Time or Traffic
Condition(or $ needed) Rehabilitation
Trigger
Preventive Trigger
Original Pavement
Optimal Timing
$1
$30-$40
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ASSUMPTION: You own 300 lane miles of road & Have a budget of $1.5M for:
• pavement reconstruction• rehab • maintenance
• Typical Breakdown
• $1M for reconstruction and rehab =“worst first” scenario &
• $500K for maintenance
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Reconstruction ~ $25.00 per yd2
• (6”mill and fill with HMA @ $75/ton)
• $1M÷$25/yd2 = 40K yd2 or 5.7 LM
Cost of maintenance ~ $4 per yd2
• $500K÷$4/yd2 = 125K yd2 or 17.8 LM
Total LN Mi repaired is 23.5
For 300 lane miles, road cycle will be ~13 years
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Costs of reconstruction ~ $25.00 per yd2
$500K÷$25/yd2 = 20K yd2 = 2.8 LN Mi
Cost of maintenance ~ $4.00 per yd2
$1M÷$4/yd2 = 250K yd2 = 35.5 LN Mi
Total LN Mi repaired ~ 38 For 300 lane miles, road cycle will be ~ 8 years
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• Management Support• Public understanding and
acceptance• Dedicated & Continuous
Funding• Good products and
workmanship• Contractor relationship• In house training
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Fog & Rejuvenating Seals ~$0.50 - $0.75/yd2
GME – Gilsonite Modified Emulsion ~$0.95/yd2
Chip Seals Cold Applied-▪ PMCRS-2h ~$1.75/yd2
▪ PMRE ~$2.00/yd2
Hot Applied –▪ Asphalt Rubber ~$2.75 - $3 /yd2
▪ Terminal Blends ~$2.50 - $2.75/yd2
Slurry Seals ~$1.50/yd2
Micro-Surfacing ~$1.75/yd2
Bonded Wearing Course ~$9- $10/yd2
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Benefits:
• Renews aged asphalt pavements
• Seal small voids and surface cracks
• Improve lane delineation and pavement marking
• Prevent raveling of loose aggregate with chip seals
• Prevents water penetration
Material:
• SS-1h
• CSS-1h
• CQS-1h
• PMRE
• Gilsonite Modified Emulsion
Material need to be diluted
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Light application of diluted slow-setting asphalt emulsion
Common uses Seal aged surface
Improve lane delineation Typical treatment life: 1 to 3 years
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Heavily aged, dense-graded HMA
Open-graded HMA
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Fog seal over existing chip seal
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1. Asphalt – PG graded asphalt 2. Rejuvenator - Acts to penetrate and add
additional maltenes to the asphalt matrix to restore flexibility to the binder. Good aggregates don't wear out as fast as asphalt becomes brittle
3. Gilsonite – Mined asphalt. Acts as a modifier to increase the polar content to form a film thickness that no other product can match.
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Reduces raveling, by locking in fines in mat. Blacker surface for better line delineation allows us to use blast furnace slag to help
restore the loss of minor fines and improve the skid numbers.
Department of Defense only uses GilsoniteModified Emulsion to reduce (FOD) Foreign Object Debris (Proprietary product known as GSB-88)
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Application rate: 0.45 to 0.70 l/m2 (0.10 to 0.15 gal/yd2)
Spray temperature range: 20 to 70 °C (70 to 160 °F)
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Spray Bar and Nozzles
Single Overlap hh
Roadway SurfaceDouble Overlap
Roadway SurfaceTriple Overlap
Roadway Surface
h
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BAD…
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Equipment inspection
Good
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Using excess emulsion for the existing pavement surface
Placing in wet and/or cool weather
Over or under dilution Incompatible water for
dilution Skid issues
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Chip Seals Chip seals consist of asphalt emulsions, asphalt rubber
binder or terminal blend binder followed by a single layer
of aggregate.
Chip seals can consist of multiple layers (single and
double chip seals), and are typically followed with a fog
seal. Chip seals can also be covered with a slurry or
microsurfacing thereby creating a “cape seal”.
Typical Treatment life: 5 – 7 years
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Chip Seals
Benefits:
• Renews aged asphalt pavements
• Improves surface friction course
(skid resistance)
• Seals small voids and surface cracks
• Improves lane delineation and pavement marking
• Prevents raveling of loose
aggregate with chip seals
• Prevents water penetration
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Polymer Modified Emulsion Chip Seal PMCRS-2h Scrub Seals PMRE (Rejuvenating Chip Seals) Usually .25-.40 gal/yd2 binder
Hot Applied Chip Seal Asphalt Rubber Chip Seal Terminal Blend (Modified Binder Chip Seal) Usually .35-.6 gal/yd2 binder
Chip over Paving Fabric .25-.35 gal/yd2 binder plus chip seal over top
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Step 4 Construction Inspection
Roll
Chip
Spray
Sweep
Sweep Again
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Start/Stop Application on Building Paper Chipper Within 100’ of Distributer Chipper Speed =NO rolling Chips Application Appears Uniform Rollers Tight to Chipper, Speed 7mph
maxChipper always within 100 feet of Distributer
NOTE DISTANCE
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Poor Workmanship
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Inadequate/Uneven Aggregate Coverage or Precoating Issues
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Polymer Modified Rejuvenating Emulsion Broom scrubs material in Emulsion + Broom = the ability to eliminate
crack filling = cost savings.
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• PMRE asphalt emulsion
• Sand or aggregate
• Broom is dragged behind the distributor
truck to embed the emulsion into the cracks
• On sand seals, pneumatic tired rollers
embed the sand into the emulsion
Scrub Seals using sand or aggregate:
SCRUB AND SAND SEALS
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SCRUB SEALS
Emulsion Wave
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Asphalt Rubber Terminal Blends
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Chip over Paving Fabric
• Low volume roads
• Good seal due to high asphalt content
•.28-.35 gal/yd2 of asphalt followed by chip seal with .3-.5 gal/yd2
of emulsion or hot applied binder
• Flexible solution for a flexible road!
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RAC/Sami 10 Years old “Ventura” warranty project
10 year old “Ventura” ARCS
Nothing done
Fabric ready for chip
Cape Seal
Terminal Blend Chip Seal
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Improper surface preparation
Applying in cool and/or wet weather
Using dirty rock Not accounting for new
patches or flushed surfaces
Not taking traffic into account
Over spreading or under spreading binder or aggregate
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Slurry SealingBenefits:
• Improved surface friction course (skid resistance)
• Seals small voids and surface cracks
• Improves lane delineation and pavement marking
• Prevents water penetration
•Typical Treatment Life: 5 – 7 years
• Can be part of a “cape seal”
(slurry seal over a chip seal)
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Existing road surface
- Laid at one-stone thickness- Largest stone bears traffic load
1/4 - 3/8”
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Micro-Surfacing
Benefits:
• Chemically driven emulsion which can reduce traffic delays to
less than 1 hour
• Improved surface friction course (skid resistance)
• Seals small voids and surface cracks
• Improves lane delineation and pavement marking
• Day or night construction
• Rut filling and re-profiling
• Prevents water penetration
•Typical Treatment life: 8 – 12 years
•Can be part of a “cape seal”
(slurry seal over a chip seal)
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Existing road surface
- Applied in multi-stone thickness
- Stone interlock and modified binder bears traffic load
- May be applied in multiple layers
3/8” +
3/8” +
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BAD
GOOD
GOOD
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Improper surface preparation or placing on badly cracked pavements
Not following the mix design Construction in wet weather Equipment not calibrated Poor workmanship, including too much water
in the mix Insufficient applications rate Inadequate QC and acceptance testing
50
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Part Chip Seal Application of .13-.25 gal/SY of a polymer
modified emulsion for adhesion Part HMA Overlay
Use of gap or open graded, polymer or rubberized HMA to finish the process
Typical Treatment Life: 8 – 12 years
What is Bonded Wearing Course
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From the chip seal
Spray application that seals the existing roadway
Bonding of the new surface to the old surface
Quick process – up to 50,000 SY per day
From the HMA overlay
Improved ride quality
Quick return to traffic
No sweeping or fog seal needed
Bonded Wearing Course
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HMA
Emulsion
Joint Matching Device
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Existing Pavement
The emulsion membrane “wicks up”around the HMA aggregates
9-12 mmcoating on aggregates
5/8”minimumDepth of Mix
3/16”Emulsionmembranedepth
The emulsion cures, bonding the mix & pavement
3/8”Nominal Ag Size
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Tack Coat Application Rate:
0.14 – 0.25 gal/yd2
Lift Thickness:
¾” – 1”
Compaction:
Method – 2 passes with a minimum of two rollers in static mode
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Machine is designed to reduce thermal and mechanical segregation
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NY-191326.351/010103YvashHR1
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Since 1998 in California
First project – Lark Ellen Blvd, Los Angeles County
Since 2002 for Caltrans
Hwy 50 over Echo Summit, Lake Tahoe
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MTC Demo Project- Before
Madison from 7th
to 8th Streets
City of Oakland
Bonded Wearing Course –Applied 2003
Bonded Wearing Course – As of
March 26, 2013
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California Chip Seal Association www.chipseal.org
Pavement Preservation Workshop, February, 2015 hosted by the California Chip Seal Association
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www.telfercompanies.com
Thank you
Hans Ho, PhDTechnical Director (Retired)[email protected](925) 228-1515 X1329