Steve Marvin - Non-destructive testing of asphalt pavements
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REMAIN CALM, ALL IS WELL What, Why and Where By Steve Marvin, P.E.
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Presentation delivered at the CalAPA Spring Asphalt Pavement Conference April 9-10, 2014 in Ontario. Topic: Non-destructive testing, including the use of both FWD and GPR testing, how they are done, results from the testing and how they are used in pavement management / preservation decision-making.
Transcript of Steve Marvin - Non-destructive testing of asphalt pavements
REMAIN CALM, ALL IS WELL
What, Why and WhereBy Steve Marvin, P.E.
Goldilocks and the Three Bears First documented testing technician
Original Goldilocks was course, ugly, smelly old woman
Goldilocks and the Three Bears First documented testing technician
Morphed to politically correct cute little girl
Initial observations
House Unlocked
Nice house
Plenty of food
Places to sleep
Tested Observations
PorridgeToo hotToo coldJust right
ChairsToo smallToo big Just right
Beds To hardTo softJust right
Things We Know
All pavements when constructed are the same
Materials Gradation Binder content Aggregate shape Aggregate Size
Things We Know
All pavements when constructed with the same
Relative compaction
Things We Know
All pavements when constructed with the same
Thickness Smoothness Surface texture Skid resistance
Things We Know
All pavements are exposed to the same Weather cycles Rainfall Landscape irrigation runoff Temperatures
Heat Cold Freezing
Things We Know
All Pavements have the same Crown Cross slope Longitudinal slope Frontage Improvements
Things We Know
All Pavements are constructed over the same soil subgrade with Identical wet and dry strengths Identical moisture contents Identical drainage characteristics
Things We Know
They are subjected to the same Axle weights Tire pressures Numbers of axle loads Travel speed
Things We Know
They are subjected to the same Vehicle operation
Speed Stopping Starting Standing Acceleration Turning movements
Things We Know
All Pavements are maintained with Same pavement seals Same crack filling Same interval of maintenance Same pavement rehabilitation,
maintenance and resurfacing
Things We Know
All pavements require Arbitrary 2” thick asphalt concrete
overlays every 10 or 20 years Identical Crack preparation Identical Local reconstruction Identical Edge milling and surface
preparation
Things We Know
No additional information is required
Things We Ignore
Axle weights increased from 18,000 to 20,000 pounds on trucks
Axle weights increased from 18,000 to 28,000 pounds on buses
Tire pressures for trucks and buses have increased to >120psi
Things We Ignore
Traffic volumes have increased
Asphalt binder characteristics are changing
Recycling is increasing
Waste reduction legislation
Things We Need to Know
Pavement construction variations What Why Where Impact
Things We Need to Know
Pavement use variations
Pavement maintenance differences
Environmental differences
How Do We Find Out?
We use pavement management to define similarities
We use engineering properties to define differences
What Sources Do We Have?
Historical plans As-built drawings Visual observations Pavement coring and potholing Ground Penetrating Radar
The Evolution of Subsurface Exploration
1970’s GPR 1970’s Oil and Mineral Deposits Archaeologists Military Big Money $$$$$$ Availability? Equipment and Power Data Capacity Mobility Trained Personnel
TODAY’S GPR
Availability Smaller Equipment Mobility Power needs Analysis time Trained Personnel Data Capacity GPS Compatibility Multiple Types
GPR: Definition
Electromagnetic Radiation Microwave band (UHF/VHF
Frequency) Radio waves transmitted into
the Ground Conductivity Increases Depth
Increases
Higher Frequencies= Low Penetration
Low Frequencies=Deep Penetration
How it Works Changes in Velocity Change in Dielectrics
Typically change in Material or Density
Components Antenna Operating System Large Data Storage
Capacity Spatial Control
GPS DMI
GPR Types
Low Frequency Applications
Less than 16 - 200 MHz Long Wave Length Deep Penetration
Range 30 Ft to 150 Ft Poor Resolution Cart Mounted or Sled
Geotechnical Mining Archeological
Investigation Ice, Snow Pack
GPR Types
Mid FrequencyApplications
270 MHz to 900 MHz Long Wave Length Not as Deep
Penetration Range 50 ft to 12 ft
Better Resolution Cart Mounted or Sled
Geotechnical Archaeological
Investigations Utility Large Subsurface Voids Ice, Snow Pack
GPR Types
High Frequency Applications
1600 MHz to 2600 MHz Short Wave Length Shallow Penetration
Range 0 Ft to 1.5 Ft Good Resolution Hand Held Device
Concrete Structures Bridge Deck (PCC)
Rebar Post Tension Cables Corrosion
GPR Types
High Frequency Applications
1 GHz to 2 GHz Short Wave Length Shallow Penetration
Range 0 Ft to 2.5 Ft Good Resolution Horn Antenna
Roadway Thickness Shallow Utility Shallow Voids
Document Pavement History
Rapid Data Acquisition
9” AC over 20” AB(Example A)
3.5” AC over 10” PCC(Example B)
PCC
4” AC over 6” AB(Example – New Pavement)
Anaheim Street (Port of Long Beach)9th Street to LA River Bridge
Carson Street(Intersection Testing)
Buried PCC
Buried PCC
Long Term/Historical Changes
Historical Changes
Historical Parking Lot Improvements
New Parking Lot Construction
Network level documentation
How is it behaving?
How strong is the roadway? Areas of strength and weakness
How does that compare with past use? Explain current behavior
How will it support projected future use? Magnitude of reinforcement required
Impacts on performance
Indirect estimates Estimates from component analysis
based on Thickness information Visible conditions In-situ moisture conditions Subgrade strengths
Impacts on performance
Direct measurement In-place strength testing
Multiple locations Magnitude of deflection Shape of deflection basin
Load/stress distribution
In place strength testing
In place strength testing
In place strength testing
In place strength testing
In place strength testing
Specific Strength Measurements
Comparative Analysis
Combined Analysis
Cost Effective Rehabilitation Strategies
Real Information
Pavement Coring Defines layer types and history
Ground Penetration Radar Provides continuous documentation of
thicknesses Estimating/Guessing
Based on past observable damage In Place Strength Testing
Permits modeling of future use and needs
Rational Engineering Judgment
Information Based
Subjective v. Objective Analysis
Empirical v. Mechanistic Analysis
SEARCHING FOR THE SIMPLE ANSWER
The Pavement Tree
