As the saying goes, Good roads cost money, and bad roads cost more. Hear the latest from the world of pavement preservation and how preservation strategies can stretch tight road maintenance dollars, as well as when maintenance becomes rehabilitation.
Hans Ho: Pavement maintenance challenges and opportunities
1. Pavement Preservation
CALIFORNIA ASPHALT
PAVEMENT ASSOCIATION
FALL ASPHALT PAVEMENT
CONFERENCE
SACRAMENTO, CA
October 29 – 30, 2014
Hans Ho, PhD
Technical Director
(Retired)
2. 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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3. Cost effectiveness
Energy savings
Reduced emissions
Reduced user costs
Life extension
User satisfaction
Safety
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6. How do I get the decision
makers to understand that
“worst first” does not work?
7. Pavement Preservation - Concept
Preventive
Trigger
Condition
(or $
needed) Rehabilitation
Time or Traffic
Trigger
Original Pavement
Optimal Timing
$1
$30-$40
8. 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
9. 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
10. 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
11. • Management Support
• Public understanding and
acceptance
• Dedicated & Continuous
Funding
• Good products and
workmanship
• Contractor relationship
• In house training
14. 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
15. Light application of diluted slow-setting
asphalt emulsion
Common uses
Seal aged surface
Improve lane delineation
Typical treatment life: 1 to 3 years
19. 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.
20. 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 Gilsonite
Modified Emulsion to reduce (FOD) Foreign
Object Debris (Proprietary product known as
GSB-88)
21.
22. 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)
23. Spray Bar and Nozzles
Single Overlap hh
RoDaoduwbaley OSuvrefralacep
RoaTdrwipaley OSuvrefralacep
Roadway Surface
h
26. 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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27. 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
28. 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
29. 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
31. 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
max
Chipper always within
100 feet of Distributer
NOTE DISTANCE
35. Polymer Modified Rejuvenating Emulsion
Broom scrubs material in
Emulsion + Broom = the ability to eliminate
crack filling = cost savings.
36. SCRUB AND SAND SEALS
Scrub Seals using sand or aggregate:
• 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
39. 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!
40. Fabric ready for chip
RAC/Sami 10 Years old “Ventura” warranty project
10 year old “Ventura” ARCS
Nothing done
Cape Seal
Terminal Blend Chip Seal
41.
42. 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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43.
44. Slurry Sealing
Benefits:
• 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)
45. - Laid at one-stone thickness
- Largest stone bears traffic load
Existing road surface
1/4 - 3/8”
46. 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)
47. - Applied in multi-stone thickness
- Stone interlock and modified binder bears traffic load
- May be applied in multiple layers
Existing road surface
3/8” +
3/8” +
50. 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
51.
52. What is Bonded Wearing Course
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
53. Bonded Wearing Course
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
55. The emulsion membrane “wicks up”
around the HMA aggregates
9-12 mm
coating on
aggregates
Existing Pavement
5/8”
minimum
Depth of Mix
3/16”
Emulsion
membrane
depth
The emulsion cures,
bonding the mix & pavement
3/8”
Nominal
Ag Size
56. 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