asphalt 105: equipment

2009 RMAC Annual Meeting

Asphalt 105: Equipment

Sub-Grade Preparation-Equipment

Compaction & Grading

Speaker: Steve McCown

Market Professional

Caterpillar Paving Products

Peoria, IL

2009 RMAC Annual Meeting

The Real World

Todays Reality for most contracting agencies is…..

•The majority of our budget dollars are spent on maintenance and rehabilitation of existing roads.

WHY?

Growth Happens!

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The Real World

Our challenge is not the proper construction of new roads but how to better manage the dollars we have to improve & maintain our existing streets and highways.

Public Pressure/Perception

Media attention

Loss of Revenues

Ability to draw new business and development

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Evolution of a Road

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Evolution of a Road

•Dirt road light traffic light loads.

•Improved Dirt road with layer of gravel

•Widened Dirt road for 2-way traffic

•Improved with asphalt for increased traffic/loads

•Entered maintenance mode….

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Typical Fix - Overlay• Re-paving on top of a

weak base is a short term fix

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Typical Fix - Mill & Fill

•Alternative for mildly distressed roads where re-profiling is needed.

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Cold Planing Process• Cold planing removes

a portion of the asphalt layer (profiling)

• Process suitable when base is in good condition and will support axle loads

• Process suitable when cracks do not extend full depth of asphalt layer

Asphalt Layer

Aggregate Base

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Cold Planing Process• Cold planing does not

remedy base problems

• Process does not remove cracks that penetrate to base

• New asphalt layer will show reflective crack quickly

• Poor economics (future maintenance)

Asphalt Layer

Aggregate Basecrack

void

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Typical Fix - Reconstruction Process

• Scarification of existing pavement

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Typical Reconstruction Process

• Removal of the scarified material

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Typical Reconstruction Process

• Material hauled to dump site for later processing as RAP.

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The Full Depth Reclamation alternative

• It is a Process, Performed in Cold, which pulverizes and mixes Existingpavement structure In Place with a certain amount of Underlying Base Material to form an Improved and Upgraded Road Base

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Full Depth Reclamation

• Proven process that provides quality results economically

• Fast-growing maintenance alternative

• Easily adapts to current highway maintenance design criteria

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Full Depth Reclamation

• Process is different from cold planing or cold-in-place recycling

• Rotor always penetrates through the asphalt into the base

• Rotor depth can be set to blend desired portion of the existing base/sub-base with the asphalt layer

Asphalt

Aggregate BaseReclaimed Material

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Full Depth Reclamation Process• Eliminates full depth

cracking• Opens base for

stabilization• Provides better

support for new asphalt layer

• Cost savings by re-using existing pavement material and done in-place

Asphalt LayerAggregate Base

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Major Indicators for Full Depth Reclamation

• Deep cracking• Reflective cracking• Pothole patching• Rutting/shoving• Frost heaves• Parabolic shape• Insufficient base

strength

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Reclaimed Material• Material leaving mixing

chamber well-graded & homogenous

• Pulverized material will not be smaller than the original aggregates

• Normal max. particle size of 50 mm (2")

• Eliminates cracks, ruts, bumps & potholes in asphalt layer

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Common Stabilizing Agents

• Asphalt emulsion• Foamed asphalt• Portland cement• Fly ash• Dry lime• Lime slurry• Calcium chloride

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Benefits of Full Depth Reclamation

• Aggregate can be added to base

• Perfect use for RAP!• Work is done in-place,

saving expensive removal & replacement of deteriorated layers

• Versatility in the process as well as the types of structures

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Secondary Road Reclamation

• Roads not designed to support today’s higher traffic volume & loads

• High opportunity for reclamation on secondary roads

• Ideal candidates for both strengthening & widening

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City Street Reclamation

• Where frequent cracking & patching are present

• Can be substituted for overlay or cold planing

• With adequate traffic control, street can remain open

• Businesses and home owners benefit from open road

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State Road Reclamation

• Higher quality structures rehabilitated with corresponding gains in base strength

• 0,8 to 1,6 km (1/2 to 1 mile) of two-lane road processed per day

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Interstate Highway Reclamation

• Portion of asphalt layer milled & remaining asphalt is pulverized & blended with the base

• Full asphalt layer is recycled or reclaimed

• Thinner wear course maybe possible

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Airport Reclamation

• Reclamation rather than overlay eliminates reflective cracking

• New surface on top of upgraded, uniformly compacted base

• Life of the new asphalt structure is increased

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Pre-Project Evaluation• Core Sampling

– asphalt layer– base/sub-base– sub-grade

• Pavement Condition Survey – buried obstacles– cracking– rutting/shoving– settlement– heaving– potholes

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Granular Materials & Soils – Lab Tests

• Attenberg Limits – ASTM D 4318• Sand Equivalent Value – ASTM D 2419• Sieve Analysis – ASTM C 136• Materials finer than No. 200 sieve – ASTM C 177

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75 mm (3") Asphalt or Less – Lab Tests

• Extraction of Bitumen – ASTM D 2172• Sieve Analysis – ASTM C 136• Materials finer than No. 200 sieve – ASTM C 177

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75 mm (3") Asphalt or More – Lab Tests

• Recovery of Asphalt – ASTM D 1856• Penetration of Bituminous Materials – ASTM D 5• Viscosity of Asphalt – ASTM D 2171

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Equipment Requirements• Full Depth Reclamation Process

– reclaiming machine (with additive system)– motor grader(s)– compactor(s)

• Auxiliary Equipment (all may not be required)– tanker truck (water, emulsion)– end or bottom dump trucks– water distributor truck– wheel loader– oil distributor truck (fog/curing seal)

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Full Depth Reclamation Process• First step is to

pulverize existing asphalt layer with portion of the base

• Sizing is controlled by operator who balances machine speed & rear door opening

• Typical sizing specs– 100% 50 mm (2")– 95% 38 mm (1.5")– 25% max. fines

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Additive Application

• Additives applied after pulverization or after rough grading

• Sprayed through on-board emulsion spray system or tanker truck

• Pulverization & mixing passes are usually separate for better consistency

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Additive Application

• Additives are often applied directly to the pulverized material

• Amounts are specified in liters sq/m gal (sq/yd)

• Additional aggregate can also be added after pulverization if required. Perfect use for RAP!

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Mixing Passes• Multiple passes may

be needed to achieve adequate homogeneity

• Sequence of mixing passes depends on the additive characteristics

• Mixing depth needs to match the pulverization depth to ensure consistent material

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Compaction of Reclaimed Material

• Normally after the mixing pass if additives are used

• Delayed if asphalt emulsion is used

• Typical compaction sequence– initial or breakdown– intermediate – finish

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Shaping Reclaimed Material• Performed after

breakdown compaction• Final shaping occurs

after crown & grade are established & all compaction is complete

• Loose material should be removed for proper bonding of the asphalt prime coat or curing seal

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Curing of Stabilized Base• Required for

development of strength & minimization ofshrinkage cracks in portland cement or fly ash

• In asphalt emulsion –water loss is required for base to set & harden

• Heavy traffic not allowed during curing – may cause base

failure

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Quality Control

• Gradation• Additive content• Moisture content• Mix uniformity• Compaction• Layer thickness• Finished surface

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Placing the Pavement Layer• May follow

pulverization, shaping & compaction, if no stabilizing agents were utilized

• May be possible to apply a thinner asphalt layer or economical chip seal

• Purpose of reclamation – creation of a higher

value, stronger base

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Typical Asphalt Pavement Structure

Hot Mix Asphalt

Crushed Stone Base

Sand & Gravel Sub-base

Sub-grade

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Construction Materials Coefficients

HMA a1 = 0.42 D1 = 125 mm (5")

CSB a2 = 0.14 D2 = 150 mm (6")

Sand a3 = 0.11 D3 = 200 mm (8")& Gravel

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Structural Number (SN) Formula

Example:SN = (0.42)(5) + (0.14)(6) + (0.11)(8)SN = 2.1 + 0.84 + 0.88SN = 3.82

SN = a1D1 + a2D2 + a3D3

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Determining the Structural Number

• Class of road – (terminal serviceability typical 3.0 - 5.0)• Climatic conditions • Sub-grade soil support value • Equivalent wheel load repetitions• Expected life before major maintenance

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HMA a1 = 0.42 D1 = 125 mm (5")

CSB a2 = 0.14 D2 = 150 mm (6")

Sand a3 = 0.11 D3 = 200 mm (8")& Gravel

New Pavement Structure

SN = 3.88 Life Expectancy = 15 Years Terminal Serviceability = 2.00

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Pavement Structure after 15 Years

Present Serviceability = 1.44 Terminal Serviceability = 2.00

Deteriorated HMA a1 = 0.42 D1 = 125 mm (5")

Decompacted CSB a2 = 0.14 D2 = 150 mm (6")

Decompacted Sand a3 = 0.11 D3 = 200 mm (8")& Gravel

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Rehabilitation Techniques• 75 mm (3") HMA overlay

• Reconstruction– mill full depth asphalt removal– re-shape and compact existing crushed stone base– 125 mm (5") HMA overlay

• Full depth reclamation– 200 mm (8") asphalt and base pulverization– stabilize with 7,57 L (2 gal/sq yd) asphalt emulsion– 75 mm (3") HMA overlay

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Overlay Alternative

SN = 2.85

HMA Overlay a1 = 0.42 D1 = 75 mm (3")Deteriorated HMA a2 = 0.15 D2 = 125 mm (5")

Decompacted CSB a3 = 0.06 D3 = 150 mm (6")

Decompacted Sand a4 = 0.06 D4 = 200 mm (8")& Gravel

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Mill & Fill Alternative

SN = 2.22

HMA Overlay a1 = 0.42 D1 = 75 mm (3")Deteriorated HMA a2 = 0.06 D2 = 125 mm (2")

Decompacted CSB a3 = 0.06 D3 = 150 mm (6")

Decompacted Sand a4 = 0.06 D4 = 200 mm (8")& Gravel

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Reconstruction Alternative

SN = 3.50

HMA Overlay a1 = 0.42 D1 = 125 mm (5")

Reconstructed CSB a2 = 0.14 D2 = 150 mm (6")

Decompacted Sand a3 = 0.07 D3 = 200 mm (8")& Gravel

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Reclamation Alternative

SN = 4.01

HMA overlay a1 = 0.42 D1 = 75 mm (3")

Reclaimed ATBa2 = 0.25 D2 = 200 mm (8")

Decompacted CSB a3 = 0.09 D3 = 75 mm (3")

Decompacted Sand a4 = 0.06 D4 = 200 mm (8")Gravel

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Structural Number Comparison

Technique SNOverlay 2.853” Mill & Fill 2.22Reconstruction 3.50Full Depth Reclamation 4.01

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Estimated Service Life

Technique SN LifeReclamation 4.01 18 years Reconstruction 3.50 15 years Overlay 2.85 12 years

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Example Only:  Cost per Square Yard Cost per Mile

Leveling Course, 1" (25 mm) avg. hot mix $4.40* $77,440.00

Wearing Course, 3" (76 mm) (hot mix) $13.20* $232,320.00

Total estimated cost for one mile $17.60* $309,760.00

Overlay. The process: Place and compact leveling course with average 1 inch (25 mm) hot mix asphalt concrete. Place and compact 3 inch (76 mm) wearing course of hot mix asphalt concrete.

Typical Overlay Project

* Based on asphalt price of $80/ton

2009 RMAC Annual Meeting

Example Only:  Cost per Square Yard Cost per Mile

Leveling Course, 1" (25 mm) avg. hot mix $4.40* $77,440.00

Wearing Course, 2" (50 mm) (hot mix) $8.80* $154,880.00

Total estimated cost for one mile $13.20* $232,320.00

Overlay. The process: Place and compact leveling course with average 1 inch (25 mm) hot mix asphalt. Place and compact 2 inch (50 mm) wearing course of hot mix asphalt concrete.

Typical Overlay Project

* Based on asphalt price of $80/ton

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Typical Reclamation Project

Full Depth Reclamation. The process: Pulverize the existing roadway structure and shoulder material to a width of 30 feet (9.1 m) and a depth of 6 inches (152 mm), reshape and mix asphalt emulsion at a rate of 2.0 gallons (7.6 liters) per square yard (square meter) to a depth of 6 inches (152 mm). Shape and compact the emulsion treated base, apply fog seal and allow to cure. Finish with a hot mix asphalt wearing course after proper curing period.

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Typical Reclamation ProjectExample Only: Cost per Square Yard Cost per Mile

Pulverizing $0.79 $13,904.00

Grade Preparation $0.26 $ 4,576.00

Water $0.11 $ 1,936.00

Mixing $0.53 $ 9,328.00

Emulsion $3.36 $47,168.00

Grading and Compaction $0.42 $ 7,392.00

Fog Seal $0.17 $ 2,992.00

3-inch Hot Mix $13.20 $232,320.00

Total Estimated Cost for One Mile $18. 84 $331,584.00

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Expected Service Life/Cost Comparison

Expected Service Life/Cost Comparison. While many factors influence the useful life of any road or street, there has been sufficient experience with full-depth reclamation to predict service life (assuming minimal maintenance). In the above example, using asphalt emulsion for added binder in the new base and a 3“ (76 mm) wearing course, an 18-year life for the reclaimed structure is expected.

The same street or road corrected with leveling course and a 3“ (76 mm) wearing course, has a projected life of 12 years. The potential for reflective cracking and accelerated deterioration is much greater on overlaid surface than on reclaimed and paved structures. Therefore, the reclaimed road will last longer and provide better long-term value.

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Expected Service Life/Cost Comparison

Initial Cost per Mile Service Life Before Major Maintenance

Cost/Year Per Mile

Reclaimed Road $331,584.00 18 years $18,421.00

Overlaid Road 3” $309,760.00 12 years? $25,813.00

Overlaid Road 2” $232,320.00 8 years? $29,040.00

Even though the initial cost to reclaim and pave with hot mix asphalt is usually about 15-30% higher than the overlay method, in the long term, full depth reclamation is about 20-40% more economical because reclaimed roads last longer!

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Structural Layer Coefficients (AASHTO)

• Sandy Gravel 0.07• Crushed Stone 0.14• Cement Treated (not soil cement) compressive strength at 7 days

– 650 psi or more 0.23– 400 psi to 650 psi 0.20– 400 psi or less 0.15

• Bituminous Treated (ATB)– course-graded 0.20 – 0.30– sand asphalt 0.30

• Lime Treated 0.15 – 0.30

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Other Benefits

• Less Fuel Consumed• Fewer Emissions• Less Traffic Disruption• Less Business

Interruption• Preserve Natural

Resources

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QUESTIONS?

Thank You!

2009 RMAC Annual Meeting

© Caterpillar 2009