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: tic@epd.engr.wisc.edu

TIC Website: http://tic.engr.wisc.edu

pudloski@engr.wisc.edu