techniques for prevention and remediation of non-load ... am... · nla distress is the result of...
TRANSCRIPT
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Techniques for Prevention and Remediation of Non-Load Related
Distresses on HMA Airport Pavements
Airfield Asphalt Pavement Technology Program
Project 05-07
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Problem
80 to 85% of the airfield pavements are Hot Mix Asphalt
The Majority of these are General Aviation Airfields
Limited Funding for Maintenance and Repairs
Result is non-load associated block cracking and surface distress
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Objective
To provide comprehensive technical guidance on the causes and measures required to correct and/or prevent non-load related distress on HMA airfield pavements.
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Research Team
Douglas I. HansonAMEC Earth and Environmental
Dr. Gayle King GHK, Inc
Dr. Mark BuncherThe Asphalt Institute
John DuvalThe Asphalt Institute
Phil BlankenshipThe Asphalt Institute
Mike AndersonThe Asphalt Institute
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Definitions
Block CrackingInterconnected cracks that divide the pavement into approximately rectangular pieces. range in size from approximately 1 by 1 ft to 10 ft by 10 ft. Caused mainly by volume changes within the HMA caused by daily temperature cycling (that results in daily stress/strain cycling). It is not load associated. The occurrence of block cracking usually indicates that the asphalt binder has hardened significantly.
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Definitions
Longitudinal or Transverse CrackingA poorly constructed paving lane joint.Shrinkage of the HMA pavement due to low temperatures or hardening of the asphalt binder orA reflection crack caused by cracks beneath the surface course
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Definitions
RavelingRaveling and weathering are the wearing away of the pavement surface caused by the dislodgement of aggregate particles and loss of asphalt binder. Such damage may indicate that the asphalt binder has age-hardened significantly.
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OUTLINEFactors Contributing to Non-Load Associated (NLA) Distress
Geographical Distribution of Airfields Potentially Exhibiting NLA Distress
Steps that can be taken to Prevent NLA Distresses In Airfield Pavements
Steps that can be taken to Medicate NLA Distress
Laboratory Test Procedures that can be used to define the Extent and Nature of NLA Distress
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Factors Contributing to NLA Distress
Climate,
Crude source,
Mixture variables, and
Construction variables.
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Climate
ProcessAs the temperature increases the rate of oxidation increasesResult is asphalt binder becomes more brittleWhen temperature drops – thermal stress develops – asphalt binder has lost elasticity and cannot recover and it cracks
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Asphalt Crude Source
Some asphalts age more rapidly than others
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Mixture Variables
Aggregate Absorption
PG Binder Grade
Asphalt AdditivesPolymersHydrated Lime
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Pavement Variables
Age hardening is most prominent at the surface
Aging will occur primarily in top ½ inch
Temperature of pavement will drop 6oC per inch of thickness
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Pavement variables
0
2
4
6
8
10
12
14
16
18
0 2 4 6 8 10 12
Aging Index
Air
Void
s
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Geographical Distribution
Data SourcesState Aviation Data Bases
Used MICRO PAVER pavement distress data from state aviation data bases
LTPP Bind Developed by the Federal Highway AdministrationUses 30 years of historical records to establish average high and low temperatures at hundreds of weather stations across the country.
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Geographical Distribution
States Included in the Analysis and the Number of Airports with Useable Distress Data
47
35
33
49
117
1215
83
66
35
80
33
8684
9
28
4
5
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Geographical Distribution
Size of sample16 States
781 Million Square Yards of HMA Pavement
142 Million Square Yards of Pavement with NLA Distress
Or 18.3%
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Geographical Distribution
0
10
20
30
40
50
60
70
80
LOW MEDIUM HIGH
PER
CEN
T N
LA D
ISTR
ESS
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Geographical Distribution
0
2
4
6
8
10
12
14
16
18
20
RUNWAY TAXIWAY APRON
Perc
ent N
LA D
istr
ess
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Geographical Distribution
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What do you do to prevent?
Climate,
Crude source/Binder Grade,
Mixture Design
Construction
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Crude Source/Binder Grade
Canada and the US are now using the SuperPave binder system for the purchase of asphalt binders such as a PG 64-22
SUGGESTION – Drop the low temperature PG grade one grade
Example if you should use a 58-22 use a a 58-28.
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Mix Design
The key is film thicknessTherefore
Sufficient asphaltConsider dropping the design air voids from 4% to 3 ½ % or even 3%. The result is increased asphalt and film thicknessBe sure you do not accomplish this by increasing the fines
Look at using low permeability mixes, such as SMA
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Construction
Goal is to restrict the supply of oxygen into the pavement
Therefore:Insure that you achieve compaction Then seal the pavement to zero permeability soon after placement
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What do you to Mitigate?
Implement an active pavement preservation program to include:
Preventive maintenance, Minor rehabilitation (non-structural), and Some routine maintenance activities.
The goal is to reduce aging and extend service life and in some cases restore the function of the existing pavement.Or – apply the “Right Treatment at the Right Time”
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What do you to mitigate?
0 Years
Fog seals; Chip seals, Slurry seals
Crack sealing, Ultrathin bonded wearing courses, Cape seals
In-place recycling
Reflective crack interlayer systems
Micro-surfacing
Base stabilization; Reconstruction
Pavement Condition
Curve shape determined by
materials & construction
quality, climate, etc.
Curve shape determined by
materials & construction
quality, climate, etc.
Hot mix overlays
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What do you do to mitigate?
Pavementcondition
Time
Pavement Preservation Treatments
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What do you do to mitigate?
Estimated Life Extensions (years)
Surface Treatment
Good Condition(PCI=80)
Fair Condition (PCI=60)
Poor Condition (PCI=40)
Spray Applied Seal 3 - 5 1 - 3 1 - 2 Chip Seal 7 - 10 3 - 5 1 - 3 Slurry Seal 7 – 10 3 - 5 1 - 3
Microsurfacing 8 – 12 5 - 7 2 - 4
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What do you do to mitigate?
Pavement Age
Pave
men
t Con
dito
n In
dex Pavement Mainteneance Trigger
Pavement Rehabilitation Trigger
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What do you do to mitigate?
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What do you do to mitigate?
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LABORATORY TEST PROCEDURE
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Test Procedure – DC(T)
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Summary & Conclusions
NLA Distress is the result of age hardening of the asphalt binder
As the binder hardens it loses it ductilityOxygen must penetrate the surface of the pavement to before it can react
Therefore – take steps to reduce the permeability of the pavement!!!!!!!
“Apply the right treatment at the right time”
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QUESTIONS