Transcript Full Depth Reclamation

Full Depth Reclamation
Current Practice
Testing Variability
Presented To:
Canadian User Group for Asphalt
Sunday, November 15, 2009
Delta Beausejour Hotel
Moncton, New Brunswick
Tom Dziedziejko
AME Materials Engineering
FDR
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Rehabilitation Technique that processes the
full depth of asphalt pavement and a
predetermined portion of the underlying base
materials
Uniformly pulverizes and blends to provide an
upgraded and homogeneous material
FDR Equipment
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Including some underlying
granular helps cool cutting
tools and enhances
pulverization action
Allows simultaneous injection
of stabilizing agents.
Pulverizing drum rotates in
an up-cut direction or
opposite to the forward
direction of travel.
FDR Equipment
Pug-Mill and
Expansion
Manifold
Screen Deck
Belt Scale
Crusher
Paver Laid FDR
•Recycling Trains
•Pulverize, Wind row, Pick up
Distresses That Can Be Treated
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Cracking
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Ride Quality
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Rutting, Shoving, Wash Boarding
General Deterioration
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Bumps, Localized Depressions, Cross fall correction,
Permanent Deformation
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Age, Fatigue, edge, slippage, block, longitudinal,
reflection, continuity
Raveling, Potholes, Stripping, Delamination, etc.
Inadequate Structural Capacity
Candidates for FDR
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Good Candidate
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Good But Approach with
Caution
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Potential serious underlying problems
Enhancement likely required
Candidates for FDR
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If existing pavement structure is adequate for loads
then simple pulverization and regrading may be all
that is required before applying surface.
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Corrective aggregate may be required to ensure adequate
drainage and mechanical properties of the treated material.
If structural enhancement is required then
stabilizing agents can be added
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Type of agent used should be selected based on the
properties of the material present.
Types of Stabilizing Additives
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Bituminous
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Chemical
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Foamed Asphalt
Asphalt Emulsions
Portland Cement
Lime
Fly Ash Types C and F
Kiln Dust (Lime/LKD or Cement/CKD), Cement, Lime Blends
Combinations of the above
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Bituminous additives blended with Chemical additives
Types of Stabilizing Additives
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Popularity of Recycling is spawning interest in
new stabilizers and additives
Foam Enhancing additives
 Pine Tar Emulsions
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Bituminous Additives
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Asphalt Emulsions
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Coats all aggregates with emulsion
Emulsion breaks leaving particles cemented together with
bitumen
Paving can not proceed until emulsion break is complete
Days? Weeks? Cement sometimes added to accelerate
break of emulsion
Bituminous Additives
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Foamed Asphalt
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Fast becoming the most popular choice for FDR
Small amount of water added to hot asphalt results in foam
Pulverized material needs fines present up to 20%
Foam mixes with fines present in material to form a mastic binder
Mastic spot welds to larger aggregate in material to form bonds that
hold mix together
Aggregates with PI as high as 15 treated successfully with no
special processes
Typical delay before paving - two days
Additive Selection for FDR
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FDR is a Soil Stabilization Technique
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When Bituminous Additives are used the process becomes a Hybrid
Asphalt and Soil product
Asphalt products provide a binder system
Produces a flexible material with properties that resist fatigue and
adds flexibility to the processed mat.
Additives used provide some enhancement to asphalt
interaction with soils but also impacts soil properties
similar to soil stabilization techniques.
Chemical Additives
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Lime
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Most often used where soil has
high PI (>10)
Benefits
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Mitigates effect of reactive clays
Reduces PI of soil after application
and reduces swelling potential
Decreases susceptibility to
moisture damage (stripping)
Increases tensile and compressive
strength of mix
Typical addition 1% to 3%
No Lime
2%Hydrated
Lime
Dry Strength
445 kPa
372 kPa
Wet Strength
128 kPa
223 kPa
TSR
29%
60%
Chemical Additives
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Portland Cement
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Most often used where soil has low
PI (<10)
Primarily adds strength to weak
materials
Benefits
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Increases compressive strength of
mix.
Strength increase over time
Impact on moisture susceptibility
variable (stripping)
Typical addition 1% to 2%
Excessive addition results in
potential cracking of the stabilized
soil
No Portland
Cement
With 2%
Portland
Cement
Dry Strength
276 kPa
341 kPa
Wet Strength
163 kPa
216 kPa
TSR
59%
63%
Chemical Additives
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Fly ash
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Fly ash is a pozzolan
typically requiring presence
of lime or hydrating cement
to gain strength
Some clays can react with
calcium oxide in Type C Fly
ash alone resulting in
strength gain.
Some fly ash has percentage
of lime present that allows
some hydration
Potential to Mitigate effect of
reactive clays - Lime
Slower strength gain than
cement but carries on longer
Excessive addition results in
potential cracking of
stabilized soil
No Fly Ash
With 1%
Fly Ash
Dry Strength
260 kPa
271 kPa
Wet Strength
168 kPa
292 kPa
TSR
65%
108%
Data Source: Job Report Cold Recycling
WR 2500: Foam recycling in Estes
National Park, Colorado /USA
Pre Engineering
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Rule of Thumb Engineering is the Most Costly Form of
Design
Proper Engineering Assessment should be carried out to
identify the best choice of additive.
Must consider :
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Amount of strength enhancement required.
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Type and quality of base materials present
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Pavement Structural Design – Traffic?
Drainage Characteristics
Presence of Clays and Silts
Plasticity Index
Pavement Drainage
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Ditching
Sub drains
Pre Engineering
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Thickness of existing pavement
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Optimize percent of pulverized pavement in process depth
+ 60% RAP
Identify excessively thick areas
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Over 200mm pavement depth could be a problem to
process due to equipment capacity
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Consider Pre-milling Options to reuse excess in other
parts of project. – Shoulder stabilization
Pre Engineering
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Proper Mixture Design
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Pre tender laboratory design trials to confirm additive
selected will work is advisable.
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Mix design before construction is compulsory
Testing Variability
Accurate Test Results Dictate Acceptance
•Stabilized Sample Temperature is Critical
60
Time (Minutes)
Room Temperature
55
Specimen Surface Temperature
Temperature ('C)
45
600
Poly. (Specimen Internal (core)
Temperature)
Poly. (Specimen Surface
Temperature)
40
35
30
500
400
Internal = 34oC
300
Surface = 28oC
Internal = 26oC
100
200
0
40
20
0
50
100
Time (Minutes)
150
200
250
30
25
20
15
Temperature (oC)
Surface = 24oC
25
35
300
Temp = 25 C: Strength = 360
Temp = 26 C: Strength = 340
Tensile Strength (kPa)
Dry Tensile Strength
Specimen Internal (core)
Temperature
Linear (Room Temperature)
50
Test Variability
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Strength Change with Varying Conditioning Temperature
Wet Tensile Strength
Dry Tensile Strength
600
Tensile Strength (kPa)
500
400
300
200
100
500
400
300
200
100
0
0
15
20
25
30
35
40
15
20
25
30
Temperature (oC)
Temperature (oC)
Tensile Strength Ratio
Tensile Strenght Ratio (%)
Tensile Strength (kPa)
600
160
140
120
100
80
60
40
20
0
15
20
25
30
Temperature (oC)
35
40
35
40
Testing Variability
Tensile Strength Increase with Time
o
(Cooling Time from 60 C)
Strength Increas e
500
Tensile Strength (kPA)
450
2 Hrs Room Curing
400
350
24 Hrs Room Curing
300
4 Hrs Room Curing
250
2
4
Hours
24
Testing Variability
Optimum Moisture – Field Sample – AC 2.8%
•Strength Varies with moisture content at time of compaction
Dry Tensile Strength
2100
2080
2060
2040
2020
2000
1980
1960
1940
1920
1900
Tensile Strength (kPa)
600.0
500.0
400.0
300.0
200.0
100.0
0.0
0.0
2.0
4.0
6.0
8.0
10.0
0.0
2.0
4.0
Moisture (%)
6.0
Moisture (%)
Wet Tensile Strength
400.0
Tensile Strength (kPa)
Bulk Relative Density
Dry Bulk Relative Denstiy
350.0
300.0
250.0
200.0
150.0
100.0
50.0
0.0
0.0
2.0
4.0
6.0
Moisture (%)
8.0
10.0
8.0
10.0
Conclusions
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Select FDR based on engineering design
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Selected process and enhancement should be based
on existing conditions.
Chemical treatments should be established using
Material requirements
Ensure Quality Verification Testing is
completed accurately
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Sample Temperature significantly influences
results
Thank You
Questions ?