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Transportation Information Center thanks its partners for their support and assistance
ACE Educational Seminar The Winding Roads of Dairy
Built to Work, Built to Last
Steve Pudloski, Director
Wisconsin Transportation Information Center
“The Basics of a Good Road” 1. Get water away from the road
2. Build on a firm foundation
3. Use the best materials
4. Compact all layers properly
5. Design for traffic loads and volumes
“The Basics of a Good Road” 6. Design for maintenance
7. Pave only when ready
8. Build from the bottom up
9. Protect your investment
10. Keep good records
Types of pavements & road surfaces
Asphalt
Hot mix – new or resurfaced; 7 < in. or 7 > in.
Cold mix – new or resurfaced; 7 < in or 7 > in.
Warm mix
Portland Cement Concrete
Sealcoat over Gravel – built up surface < 1 in.
Gravel
Earth
Graded and drained or not graded and drained
Brick or Block
Factors affecting pavement life
Subgrade soil
Pavement materials
Traffic loads and traffic volume
Thickness
Construction quality
Age
Maintenance
Water - drainage
Basic distress mechanisms
Moisture related
Load related
Temperature related
Age related
Moisture
Infiltration
Lubricates
Particles
Weakens
materials
1. Get water away from the road
Moisture Related Why is water a big problem under pavements?
In Subgrade Soil
Moisture
Infiltration
Into
Voids
Freezing
Water
Expands
Breaks
Material
Apart
1. Get water away from the road Moisture Related
Why is water a big problem in pavements?
in Subgrade, Aggregate Base and Asphalt Surface
1. Get water away from the road
Ditch must be below the road base.
2. Build on a firm foundation Water, Soils, and Pavements
All pavements rely on the soil beneath the pavement for support.
Wet soils provide less support causing pavements to exceed their load carrying capability and/or their range of flexibility.
Variations in soil moisture occur seasonally. Good drainage systems minimize the variation.
2. Build on a firm foundation
Native Soils and Water Soils loose strength when wet
• Lubrication of the soil particles
• Replace mineral matter with water
• Expansion of water as it freezes
Not all soils loose the same strength when wet, loss depends on
• Class (clays loose the most strength)
• Particle size
• Particle shape
• Mixture or gradation (how many voids)
2. Build on firm foundation
Subgrade soils are native soils
Mixture of mineral and organic matter with voids that are filled with water and/or air
Soil types and strengths can vary from spot to spot and from layer to layer
Load bearing strength of any given soil will vary with water content
There is an optimum water content at which a soil is most dense and will carry the greatest load. Compact at optimum water content.
Compaction Fundamentals
Typical Specification Block
95-100% of maximum dry density
OMC ± 2% moisture
Improve Poor Foundations
If Native Soils Have Poor Strength Use Chemical stabilization
• Flyash or Lime
• Portland Cement
Over Excavate, Fill with Select Material
Use Geosynthetics • Woven Geotextile
• Non-woven Geotextile
• Geogrid
• Geo Cell
Base sinks into soft subgrade
Separation
Geo-fabric
Separation & Stabilization
Geotextile used to prevent mixing of road base into subgrade soil
In subgrades with a CBR greater than or equal to 3, use Class 2 geotextiles
In subgrades with a CBR between 1 and 3, use Class 1 geotextiles
Both woven and non-woven can be used for separation application
Base the selection of fabric on your state DOT material specification
Woven Geotextile
Geotextile Separation Test Results
Minnesota LRRB tests (slit tape, heavy
woven, non-woven, & none under 4”, 6” and
8” stone) Non-woven 20% more friction than woven
NW + 4” = W + 6” = No �Geo + 8”
Anchoring fabric not necessary
Compaction of stone is important
No punctures in any of the fabrics
Oklahoma test (woven, non-woven, & none
under 4” of stone) After one winter all un-reinforced sections failed
Non-woven recommended because
• higher friction
• More permeable
Picture 1 from Oklahoma Test
Picture 2 from Oklahoma Test
Picture 3 from Oklahoma Test
Picture 4 from Oklahoma Test
Picture 5 from Oklahoma Test
Geogrid for Reinforcement
Mechanical Interlock
Openings in geogrid reinforce rock base by increasing aggregate interlock
Stress Transfer
MIDOT Highway 69
MIDOT HWY 69
MIDOT HWY 69
Logging Road – Twin Lakes, MI
Logging Road – Twin Lakes, MI
Geogrid with Geosynthetic Fabric
Geocell Confinement Systems
Geocells are 3-dimensional honeycomb-like structures filled with sand, rock or concrete.
The Geocell is made of strips of polymer sheet or geotextile connected at staggered points so that, when the strips are pulled apart, a large honey-comb mat is formed.
The Geocell provides a physical containment for a depth of soil and a transfer of load through the geocell structure.
Geocell Confinement System
Geocell System with Sand Fill
3. Use the Best Materials – Base
Aggregate Base Size of the particles
Distribution of sizes (called gradation)
Moisture content
Wear -- abrasion resistance
Hardness -- strength in compression
Fracture -- number of faces
Freeze/thaw soundness
Deleterious materials
gravel and “stone” (crushed stone)
Gravel – usually natural material - from gravel pits -rounded/weathered
Stone – crushed material – from quarry – fractured faces
Classification of Soils by Size Using Common Nomenclature
Larger than 12” – boulders
Between 12” and 3” – cobbles
Between 3” sieve and #4 – gravel
Between #4 and #200 sieves – sand
Smaller than #200 sieve – fines (silt & clay)
For particles smaller than #200 -- use hydrometer test -- “specific gravity”
How Size & Distribution are Measured
Stack of nesting sieves with the biggest openings at the top and a pan at the bottom
Pour the stone in the top, washed, shake the stack, weigh each sieve, determine percent passing each sieve
Typical Sizes of Sieves
75 mm (3 in)
50 mm ( 2 in”)
37.5 mm (1 1/2 in)
12.5 mm (1/2 in)
25 mm (1 in)
19 mm (3/4in)
12.5 mm (1/2 in)
9.5 mm (3/8 in)
4.75 mm (#4)
0.2 mm (#10)
0.0425 mm (# 40)
0.075 mm (#200)
31.5 mm (1 1/4 in)
Sieve Analysis Used to Determine
Classification of the material
Does sample meet specifications
Gradation – well, poorly, or open graded
Estimate of strength
Specific particle sizes – for filters/drains
D10, D30, D60:
Sieve size in millimeters that 10, 30 and 60%, respectively pass
Typical Grain Size Distribution
Why Use Well Graded Stone
Smaller particles fill up spaces between the larger rock to reduce air voids in the mix, thereby
increasing aggregate interlock and strengthening the structure
Stone Particles
3. Use the Best Materials – Surface
WAPA Asphalt Design Guide
Asphalt Binder Grades
4. Compact All Layers
95-100% of maximum dry density
OMC ± 2% moisture
Steel Wheeled Roller Gravels, sands, silts
May use in vibratory or static mode
Sheepsfoot Roller –
Clay
Compactor “walks” out of the soil
Pneumatic (Rubber Tired) Roller
Clays, silts, sand
Tire pressure can be adjusted
Grid Roller
Gravel, breaker-run, cobbles
Paver Screed –Key Component
Provides initial (85%) compaction
Smoothes surface
Provides slope/crown
Governs thickness
Rolling Operations for Asphalt Pavement
Compaction Phases
Breakdown (Initial)
• Provide initial compaction/density
• Use vibratory steel-wheeled roller
Intermediate
• Use vibratory steel-wheeled or pneumatic roller
Finish
• Remove roller marks – smooth surface
• Use static (non-vibratory) steel-wheeled roller
Steel Wheeled Roller
Vibratory mode for
breakdown rolling
Static mode (vibrator
off) for finish rolling
Pneumatic Roller
Often used for
Intermediate rolling
Tire pressure must be
uniform
Wheels are staggered
to provide full-width
compaction
Combination of Breakdown and Intermediate Rolling
Wheel Load
Hot-mix asphalt
Base
Subbase
Natural soil called subgrade
5. Design for Traffic Loads & Volumes
Different Pavement Types
Subbase
Subgrade
Base
Asphalt Layer
Subbase
Subgrade
Concrete Section Asphalt Section
How Pavements Carry Loads
6500 lbs 6500 lbs
pressure < 0.3 psi
pressure
3 psi
Portland Cement Concrete
Hot Mix Asphalt Concrete
Pavement Thickness Design
Adequate pavement thickness design is the result of a thorough soil survey coupled with a mathematical evaluation of such factors as vehicle volume and composition, subgrade soil support, and the strengths of materials used in the pavement structure.
Evolving Design Methodology
Empirical - - - Combination - - -Mechanistic
(Road Test) (MEPDG)
Empirical Method of Thickness Design
Design period of the pavement. In the USA 20 years is typical, although recent approach is called “perpetual” pavement, or “ long lasting” pavement
Design traffic load is estimated for 1/2 the design period. For a 20 year design period the projected ADT in year 10 is the basis of the design.
Empirical Method of Thickness Design
Calculate traffic factor for design year
Project the number and mix of vehicles
One 80,000# truck equals the loading (damage) of 7,000 to 10,000 cars
AASHTO : 18,000# per axle or 18kips Equivalent Single Axle Loads (ESALS)
Empirical formula to calculate traffic factor which will be used with soil and pavement strengths to set thickness
Soil Strength by Soil Type
Excellent to Good Soils (High Support)
Retains substantial amount of support capacity when wet.
Clean and sharp sand and gravel that are well graded, i.e., good distribution of particle sizes and low voids. Minimally affected by frost.
Medium Soils (Medium Support)
Retains moderate amount of firmness when wet. Loams, silty
sands and sand & gravel with some clay and fine silt. Some frost heaving.
Poor Soils (Poor Support)
Becomes soft and plastic when wet. High clay and silt content.
Organic soils are also poor.
Soil Capacity to Bear Loads
Field sample that is tested in the lab with the test at saturated conditions
CBR is the California Bearing Ratio
Crushed Limestone CBR = 100 Good Soil CBR = 17 Medium Soil CBR = 9 Poor Soil CBR = 3
New Measure is Resilient Modulus
Structural Number (Dt)
is an abstract number related to the strength required of the total pavement structure and is the sum of the strength of each pavement layer. It is calculated by multiplying the thickness of the layer by the strength coefficient of the layer. Dt = a1D1 + a2D2 + a3D3 a1, a2, a3 are coefficients of Strength of the surface, base, and subbase materials. D1, D2, D3 are the thickness in inches of the surface, base, and subbase materials
Structural Number
TF
IBR
Thickness Design Bulletin
Location of crack along HMA Surface
Contraction
HMA surface
Friction on Underside of HMA Surface
Tensile Stress in
HMA Surface
Existing
Crack or
Cold Joint
Existing
Crack or
Cold Joint
Temperature-Related
Age Related
Asphalt pavement oxidizes from
exposure to sunlight (Ultra-Violet
Rays cause the pavement to be less
flexible)
Life of an Asphalt Surface - 1
“Almost” New Street
Life of an Asphalt Surface - 2
“Transverse Cracking”
Life of an Asphalt Surface - 3
“Start of Block Cracking”
Life of an Asphalt Surface - 4
“Alligatoring with Pothole”
6. Design for Maintenance
Adequate road and shoulder width
Adequate ditches…deep enough & no erosion
Culverts marked for inspection and cleaning
Enough space for snow to be lowed off the road
Proper ditch cross slopes
Safe roadside clear zone
Roadside that can be mowed easily
7. Pave Only When Ready
25,000 miles of gravel road in Wisconsin
Adequate until 300 vehicles per day
Don’t assume putting on a lift of asphalt will fix a poor gravel road
Test the soil to determine syrength
Count the trucks
Don’t build a road in a bathtub --daylight the base
Adequate ditches that drain the pavement structure -- at least one foot below the bottom of the pavement structure
Adequate crushed aggregate base
8. Build from the bottom up
Road failures start at the bottom
Poor soil support
Loads exceed the design life
Poor drainage
Loss of surface integrity
Fixes of road failure often need to start at the bottom, too
http://tic.engr.wisc.edu/publications.html
Time to
Use your
PASER
rating to
plan
9. Protect your Investment
PASER rating system for paved surfaces
Pavement Rating
Overlays & Reconstruction
Surface Treatments
Routine Maintenance
Importance of preventive maintenance
Importance of preventive maintenance
Type 70 - HMAC y = -0.00005610x3 + 0.00720159x2 - 0.34291690x + 9.66382562
R2 = 0.98940032
0.0000.5001.0001.5002.0002.5003.0003.5004.0004.5005.0005.5006.0006.5007.0007.5008.0008.5009.0009.500
10.00010.500
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78
Age
Ra
tin
g
Visual Distresses in Asphalt Pavements
1. Surface Defects
2. Surface Deformation
3. Cracking
4. Potholes and Patches
Asphalt Surface Defects
Ravelling
Flushing
Polishing
Asphalt Surface Deformation
Rutting
Shoving
Settling
Frost Heave
Cracking
Transverse
Reflective
Slippage
Longitudinal
Block
Alligator
Potholes & Patches
Asphalt Pavement Treatments
Crack fill or crack seal
Chip seal
Double chip seal
Slurry seal
Fog seal
Temporary patch
Spray patch
Permanent hot patch
Infra-red patch
Thin Overlay (3/4”)
Overlay (2-3”)
Mill and Overlay
Full depth reclaim
White top with PCC
Reconstruction
Filling and Sealing Cracks
Crack sealing
prevents damage
Rout the cracks
Seal the Cracks
Sealcoats Reduce Sun Damage
Chip Seal Process -- Oil Distributor
Coat with stone chips
Place chips, one stone deep
Roll stone into the oil
Slurry Seal
Slurry is asphalt emulsion + aggregate
Wet Slurry
Cured Slurry
8 - 15 Ultrathin Bonded HMA
6 - 12 Microsurfacing
4 - 10 Slurry Seals
4 - 8 Chip Seals
2 - 4 Fog Seals
2 - 4 Crack Sealing
Years Treatment
Frequency of Preventive Maintenance
2 - 4 5 - 7 8 - 12 Thin Overlay
2 - 4 5 - 7 8 - 12 Microsurfacing
1 - 3 3 - 5 7 - 10 Slurry Seal
1 - 3 3 - 5 7 - 10 Chip Seal
1 - 2 1 - 3 3 - 5 Fog Seal
Poor Condition
Fair Condition Good Condition
Treatment
Estimated Life Extension (years)
Overlay
Overlay
Mill then Overlay
Milling / Overlays
Preheater
Preheater Heater/Scarifier
Paver Roller
Hot In-Place (Surface) Recycling
Cold In-Place Recycling
Full Depth Reclamation
Reconstruction
Utility Accommodation & Permits
Governments own the ROW and should require permits for all work in it
There should be standard locations to reduce conflicts
Inspect construction by others in ROW to stop buried mistakes and future problems
Participate in a utility coordination and planning process to coordinate future activities of all utilities with street work
Road Cuts Shorten Pavement Life
Transportation Information Center thanks its partners for their support and assistance
Steve Pudloski 608-262-8707
432 N. Lake Street
Madison, Wisconsin 53706
Toll Free: (800) 442-4615
TIC Email: [email protected]
TIC Website: http://tic.engr.wisc.edu