Transcript McCown_-_Asphalt_105_

Asphalt 105: Equipment
Sub-Grade Preparation-Equipment
Compaction & Grading
Speaker: Steve McCown
Market Professional
Caterpillar Paving Products
Peoria, IL
2009 RMAC Annual Meeting
The Real World
Todays Reality for most contracting agencies is…..
Growth Happens!
•The majority of our budget
dollars are spent on
maintenance and rehabilitation
of existing roads.
WHY?
2009 RMAC Annual Meeting
The Real World
Our challenge is not the proper construction of
new roads but how to better manage the dollars
we have to improve & maintain our existing streets
and highways.
Public Pressure/Perception
Loss of Revenues
Media attention
Ability to draw new
business and
development
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Evolution of a Road
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Evolution of a Road
•Dirt road light traffic light loads.
•Improved Dirt road with layer of gravel
•Widened Dirt road for 2-way traffic
•Improved with asphalt for increased traffic/loads
•Entered maintenance mode….
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Typical Fix - Overlay
• Re-paving on top of a
weak base is a short
term fix
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Typical Fix - Mill & Fill
•Alternative for mildly
distressed roads where
re-profiling is needed.
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Cold Planing Process
• Cold planing does not
remedy base
problems
• Process does not
remove cracks that
penetrate to base
Asphalt Layer
crack
Aggregate Base
• New asphalt layer will
show reflective crack
quickly
void
• Poor economics
(future maintenance)
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Typical Reconstruction Process
• Removal of the
scarified material
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Typical Reconstruction Process
• Material hauled to
dump site for later
processing as RAP.
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The Full Depth Reclamation alternative
• It is a Process,
Performed in Cold,
which pulverizes and
mixes Existing
pavement structure In
Place with a certain
amount of Underlying
Base Material to form
an Improved and
Upgraded Road Base
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Full Depth Reclamation
• Proven process that
provides quality
results economically
• Fast-growing
maintenance
alternative
• Easily adapts to
current highway
maintenance design
criteria
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Full Depth Reclamation
• Process is different
from cold planing or
cold-in-place recycling
Asphalt
Aggregate Base
• Rotor always
penetrates through the
asphalt into the base
Reclaimed Material
• Rotor depth can be set
to blend desired
portion of the existing
base/sub-base with the
asphalt layer
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Full Depth Reclamation Process
• Eliminates full depth
cracking
• Opens base for
stabilization
Asphalt Layer
Aggregate Base
• Provides better
support for new
asphalt layer
• Cost savings by
re-using existing
pavement material
and done in-place
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Major Indicators for Full Depth Reclamation
• Deep cracking
• Reflective cracking
• Pothole patching
• Rutting/shoving
• Frost heaves
• Parabolic shape
• Insufficient base
strength
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Reclaimed Material
• Material leaving mixing
chamber well-graded &
homogenous
• Pulverized material will
not be smaller than the
original aggregates
• Normal max. particle
size of 50 mm (2")
• Eliminates cracks, ruts,
bumps & potholes in
asphalt layer
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Common Stabilizing Agents
• Asphalt emulsion
• Foamed asphalt
• Portland cement
• Fly ash
• Dry lime
• Lime slurry
• Calcium chloride
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Benefits of Full Depth Reclamation
• Aggregate can be
added to base
• Perfect use for RAP!
• Work is done in-place,
saving expensive
removal & replacement
of deteriorated layers
• Versatility in the
process as well as the
types of structures
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Secondary Road Reclamation
• Roads not designed
to support today’s
higher traffic volume
& loads
• High opportunity
for reclamation
on secondary roads
• Ideal candidates
for both strengthening
& widening
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City Street Reclamation
• Where frequent
cracking & patching
are present
• Can be substituted for
overlay or cold planing
• With adequate traffic
control, street can
remain open
• Businesses and home
owners benefit from
open road
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State Road Reclamation
• Higher quality
structures rehabilitated
with corresponding
gains in base strength
• 0,8 to 1,6 km
(1/2 to 1 mile) of
two-lane road
processed per day
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Interstate Highway Reclamation
• Portion of asphalt
layer milled &
remaining asphalt is
pulverized & blended
with the base
• Full asphalt layer is
recycled or reclaimed
• Thinner wear course
maybe possible
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Airport Reclamation
• Reclamation rather
than overlay eliminates
reflective cracking
• New surface on top
of upgraded, uniformly
compacted base
• Life of the new asphalt
structure is increased
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Pre-Project Evaluation
• Core Sampling
– asphalt layer
– base/sub-base
– sub-grade
• Pavement Condition
Survey
– buried obstacles
– cracking
– rutting/shoving
– settlement
– heaving
– potholes
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Equipment Requirements
• Full Depth Reclamation Process
– reclaiming machine (with additive system)
– motor grader(s)
– compactor(s)
• Auxiliary Equipment (all may not be required)
– tanker truck (water, emulsion)
– end or bottom dump trucks
– water distributor truck
– wheel loader
– oil distributor truck (fog/curing seal)
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Full Depth Reclamation Process
• First step is to
pulverize existing
asphalt layer with
portion of the base
• Sizing is controlled by
operator who balances
machine speed & rear
door opening
• Typical sizing specs
– 100% 50 mm (2")
– 95% 38 mm (1.5")
– 25% max. fines
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Additive Application
• Additives applied after
pulverization or after
rough grading
• Sprayed through onboard emulsion spray
system or tanker truck
• Pulverization & mixing
passes are usually
separate for better
consistency
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Additive Application
• Additives are often
applied directly to the
pulverized material
• Amounts are specified
in liters sq/m
gal (sq/yd)
• Additional aggregate
can also be added
after pulverization
if required. Perfect use
for RAP!
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Mixing Passes
• Multiple passes may
be needed to achieve
adequate homogeneity
• Sequence of mixing
passes depends
on the additive
characteristics
• Mixing depth needs
to match the
pulverization depth
to ensure consistent
material
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Compaction of Reclaimed Material
• Normally after the
mixing pass if
additives are used
• Delayed if asphalt
emulsion is used
• Typical compaction
sequence
– initial or breakdown
– intermediate
– finish
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Shaping Reclaimed Material
• Performed after
breakdown compaction
• Final shaping occurs
after crown & grade
are established & all
compaction is
complete
• Loose material should
be removed for proper
bonding of the asphalt
prime coat or curing
seal
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Curing of Stabilized Base
• Required for
development of strength
& minimization of
shrinkage cracks in
portland cement or
fly ash
• In asphalt emulsion –
water loss is required
for base to set & harden
• Heavy traffic not
allowed during curing
– may cause base
failure
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Quality Control
• Gradation
• Additive content
• Moisture content
• Mix uniformity
• Compaction
• Layer thickness
• Finished surface
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Placing the Pavement Layer
• May follow
pulverization, shaping
& compaction, if no
stabilizing agents were
utilized
• May be possible to
apply a thinner asphalt
layer or economical
chip seal
• Purpose of reclamation
– creation of a higher
value, stronger base
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Typical Asphalt Pavement Structure
Hot Mix Asphalt
Crushed Stone Base
Sand & Gravel Sub-base
Sub-grade
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Construction Materials Coefficients
HMA
a1 = 0.42
D1 = 125 mm (5")
CSB
a2 = 0.14
D2 = 150 mm (6")
Sand
a3 = 0.11
& Gravel
D3 = 200 mm (8")
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Structural Number (SN) Formula
SN = a1D1 + a2D2 + a3D3
Example:
SN = (0.42)(5) + (0.14)(6) + (0.11)(8)
SN = 2.1 + 0.84 + 0.88
SN = 3.82
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Determining the Structural Number
• Class of road – (terminal serviceability typical 3.0 - 5.0)
• Climatic conditions
• Sub-grade soil support value
• Equivalent wheel load repetitions
• Expected life before major maintenance
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New Pavement Structure
HMA
a1 = 0.42
D1 = 125 mm (5")
CSB
a2 = 0.14
D2 = 150 mm (6")
Sand
a3 = 0.11
& Gravel
D3 = 200 mm (8")
SN = 3.88 Life Expectancy = 15 Years Terminal Serviceability = 2.00
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Pavement Structure after 15 Years
Deteriorated HMA
a1 = 0.42
D1 = 125 mm (5")
Decompacted CSB
a2 = 0.14
D2 = 150 mm (6")
Decompacted Sand
& Gravel
a3 = 0.11
D3 = 200 mm (8")
Present Serviceability = 1.44 Terminal Serviceability = 2.00
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Overlay Alternative
HMA Overlay
a1 = 0.42
D1 = 75 mm (3")
Deteriorated HMA
a2 = 0.15
D2 = 125 mm (5")
Decompacted CSB
a3 = 0.06
D3 = 150 mm (6")
Decompacted Sand
& Gravel
a4 = 0.06
D4 = 200 mm (8")
SN = 2.85
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Mill & Fill Alternative
HMA Overlay
a1 = 0.42
D1 = 75 mm (3")
Deteriorated HMA
a2 = 0.06
D2 = 125 mm (2")
Decompacted CSB
a3 = 0.06
D3 = 150 mm (6")
Decompacted Sand
& Gravel
a4 = 0.06
D4 = 200 mm (8")
SN = 2.22
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Reconstruction Alternative
HMA Overlay
a1 = 0.42
D1 = 125 mm (5")
Reconstructed CSB
a2 = 0.14
D2 = 150 mm (6")
Decompacted Sand
& Gravel
a3 = 0.07
D3 = 200 mm (8")
SN = 3.50
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Reclamation Alternative
HMA overlay
a1 = 0.42
Reclaimed ATBa2 = 0.25
D1 = 75 mm (3")
D2 = 200 mm (8")
Decompacted CSB
a3 = 0.09
D3 = 75 mm (3")
Decompacted Sand
Gravel
a4 = 0.06
D4 = 200 mm (8")
SN = 4.01
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Structural Number Comparison
Technique
SN
Overlay
3” Mill & Fill
Reconstruction
Full Depth Reclamation
2.85
2.22
3.50
4.01
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Estimated Service Life
Technique
SN
Life
Reclamation
Reconstruction
Overlay
4.01
3.50
2.85
18 years
15 years
12 years
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Typical Overlay Project
Overlay. The process: Place and compact leveling course with average 1
inch (25 mm) hot mix asphalt concrete. Place and compact 3 inch (76 mm)
wearing course of hot mix asphalt concrete.
Example Only:
Cost per Square Yard
Cost per Mile
Leveling Course, 1" (25 mm) avg. hot mix
$4.40*
$77,440.00
Wearing Course, 3" (76 mm) (hot mix)
$13.20*
$232,320.00
Total estimated cost for one mile
$17.60*
$309,760.00
* Based on asphalt price of $80/ton
2009 RMAC Annual Meeting
Typical Overlay Project
Overlay. The process: Place and compact leveling course with average 1
inch (25 mm) hot mix asphalt. Place and compact 2 inch (50 mm) wearing
course of hot mix asphalt concrete.
Example Only:
Cost per Square Yard
Cost per Mile
Leveling Course, 1" (25 mm) avg. hot mix
$4.40*
$77,440.00
Wearing Course, 2" (50 mm) (hot mix)
$8.80*
$154,880.00
Total estimated cost for one mile
$13.20*
$232,320.00
* Based on asphalt price of $80/ton
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Typical Reclamation Project
Full Depth Reclamation. The process: Pulverize the existing roadway
structure and shoulder material to a width of 30 feet (9.1 m) and a depth of 6
inches (152 mm), reshape and mix asphalt emulsion at a rate of 2.0 gallons
(7.6 liters) per square yard (square meter) to a depth of 6 inches (152 mm).
Shape and compact the emulsion treated base, apply fog seal and allow to
cure. Finish with a hot mix asphalt wearing course after proper curing period.
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Typical Reclamation Project
Example Only:
Pulverizing
Cost per Square Yard
$0.79
$13,904.00
$0.26
Grade Preparation
Cost per Mile
$
4,576.00
Water
$0.11
$ 1,936.00
Mixing
$0.53
$ 9,328.00
$3.36
Emulsion
$47,168.00
Grading and Compaction
$0.42
$ 7,392.00
$0.17
Fog Seal
$
2,992.00
3-inch Hot Mix
Total Estimated Cost for One Mile
$13.20
$232,320.00
$18. 84
$331,584.00
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Expected Service Life/Cost Comparison
Expected Service Life/Cost Comparison. While many factors influence
the useful life of any road or street, there has been sufficient experience
with full-depth reclamation to predict service life (assuming minimal
maintenance). In the above example, using asphalt emulsion for added
binder in the new base and a 3“ (76 mm) wearing course, an 18-year life
for the reclaimed structure is expected.
The same street or road corrected with leveling course and a 3“ (76 mm)
wearing course, has a projected life of 12 years. The potential for
reflective cracking and accelerated deterioration is much greater on
overlaid surface than on reclaimed and paved structures. Therefore, the
reclaimed road will last longer and provide better long-term value.
2009 RMAC Annual Meeting
Expected Service Life/Cost Comparison
Initial Cost per Mile Service Life Before Cost/Year Per Mile
Major Maintenance
Reclaimed Road
$18,421.00
$331,584.00
18 years
Overlaid Road 3”
$25,813.00
$309,760.00
12 years?
Overlaid
years?
Even Road
though2”the initial cost to $232,320.00
reclaim and pave8with
hot mix asphalt is
$29,040.00
usually
about 15-30% higher than the overlay method, in the long term,
full depth reclamation is about 20-40% more economical because
reclaimed roads last longer!
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Other Benefits
• Less Fuel Consumed
• Fewer Emissions
• Less Traffic Disruption
• Less Business
Interruption
• Preserve Natural
Resources
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Thank You!
QUESTIONS?
2009 RMAC Annual Meeting
© Caterpillar 2009
2009 RMAC Annual Meeting