October 9, 2008 Spokane, Washington Fundamentals of Design and Construction of Full-Depth Reclamation Pavements The Washington State County Road Administration.

October 9, 2008Spokane, Washington

Fundamentals of DesignFundamentals of Designand Construction ofand Construction of

Full-Depth Reclamation Full-Depth Reclamation PavementsPavements

The Washington State County Road Administration The Washington State County Road Administration BoardBoard

Designing for Society:Designing for Society:Knowledge, Innovation, and SustainabilityKnowledge, Innovation, and Sustainability

Gregory E. Halsted, P.E.Program Manager – SC/RCC PavementsPortland Cement Association

Since its founding in 1916, the Portland Cement Association has had the same mission:"Improve and expand the uses of portland cement and concrete."

Divisions• Market Promotion• Research• Technical Services• Codes and Standards

Affiliates• American Concrete Pavement Association• The CTL Group• Cement Association of Canada

Regional Promotion GroupsRegional Promotion Groups

Water Content

Cem

ent

Co

nte

nt

Cast

Rolled

No Wearing Course RequiredWearing Course Required

Roller-Compacted Concrete

Conventional Concrete

Soil-Cement

Flowable Fill

Cement-Modified Soil

Full-DepthReclamation

Cement-Treated Base

Cement-Based Pavement Cement-Based Pavement MaterialsMaterials

PerviousConcrete

Hydration Products

• all particles not coated• voids not filled• linkages bind soil agglomerations together

Cementitious Gel or Paste

• coats all particles• fills voids

ConcreteConcrete Soil-CementSoil-Cement

Soil-Cement Materials in a Soil-Cement Materials in a Pavement SectionPavement Section

Cement-Modified Soil (CMS)Cement-Modified Soil (CMS)

The objective of CMS is to amend undesirable

properties of problem soils or substandard materials so that they are suitable for use in construction. The amount of cement added to the soil is less than that required to produce a hardened mass

but is enough to improve the engineering properties of the

soil.

Reasons to ModifyReasons to Modify• Improve the properties of the subgrade

soil–Reduce volume change caused by moisture– Improve wet strength– Improve compactibility

• Expedite construction by improving subgrade support in wet weather–Eliminate muddy construction sites–Create an all-weather work platform

It is important to remember thatsoil modification is different than soil stabilization

Benefits of Cement-Modified SoilBenefits of Cement-Modified Soil• Small addition of cement

to soils to change properties

• Eliminates need for removal/replacement of inferior soils

• Low cost soil improvement• Improves pavement

support• Forms weather-resistant

work platform• Provides permanent non-

leaching modification

Cement-Treated Base (CTB)Cement-Treated Base (CTB)

CTB refers to an intimate mixture of soils and/or

aggregates with measured amounts of portland cement and water that hardens after

compaction and curing to form a strong, durable, frost

resistant paving material. CTB can be mixed in place using on-site materials, or

mixed in a central plant using selected material.

What is CTB?What is CTB?

• Extremely dense• Intimately blended• Highly compacted• Mixture of

Aggregates or soil or combinations Portland cement Water

• Base or subbase for either concrete or bituminous surfacing

• Stable platform as a building pad• Provides wet-dry and freeze-thaw

durability

Why Use CTB?Why Use CTB?

• Low first cost and life cycle cost

• Allows thinner pavement sections

• Can use in-situ materials

• Reduces use of virgin aggregates

• Reduces moisture susceptibility

• Frost resistant• Spans weak subgrades

Full-Depth Reclamation (FDR)Full-Depth Reclamation (FDR)

The FDR process pulverizes the existing asphalt and blends it with underlying base, subbase, and/or

subgrade materials, which are mixed with cement to provide a new stabilized

base. A new surface is then applied, providing a new roadway structure using

recycled materials from the failed pavement.

Definition of ReclamationDefinition of Reclamation• Method of flexible pavement reconstruction that utilizes

the existing asphalt, base, and subgrade material to produce a new stabilized base course for a chip seal, asphalt, or concrete wearing surface.

• Alternative Terms:– Full-Depth Recycling (FDR)– Full-Depth Rehabilitation (FDR)– Cement Recycled Asphalt Base Stabilization (CRABS)– Cement-Treated Base (CTB)– Cement-Treated Existing Roadway Materials (C-TERM)– Cement Stabilized Reclaimed Base (CSRB)– Full-Depth Reclamation with Portland Cement (FDR-PC)

Challenges FacingChallenges FacingAmerica’s RoadwaysAmerica’s Roadways

Challenges FacingChallenges FacingAmerica’s RoadwaysAmerica’s Roadways

• Continuing Growth• Rising Expectations from Users• A Heavily Used, Aging System• Environmental Compatibility• Changes in the Workforce• Funding Limitations

Combined with large increases in traffic volumes and/or allowable loads often leads to serious roadway base failures!

How do you know if you haveHow do you know if you havea base problem and not justa base problem and not just

a surface deficiency?a surface deficiency?

Examples of Pavement DistressExamples of Pavement Distress• Alligator Cracking• Rutting• Excessive Patching• Base Failures• Potholes• Soil Stains on Surface

Advantages of ReclamationAdvantages of Reclamation

• Use of in-place materials• Little or no material

hauled off and dumped• Maintains or improves

existing grade• Conserves virgin material• Saves cost by using

in-place “investment”• Saves energy by reducing

mining and hauls• Environmentally friendly

Engineering BenefitsEngineering Benefits

• Increased Rigidity Spreads Loads• Eliminates Rutting Below Surface• Reduced Moisture Susceptibility• Reduced Fatigue Cracking• Thinner Pavement Section• Retards Reflective Cracking

DESIGNDESIGN

Obtain representative samplesObtain representative samplesfull length, width, and depth!full length, width, and depth!

Laboratory TestsLaboratory Tests

• Sieve Analysis (ASTM C136)• Atterberg Limits (ASTM D4318)• Moisture-Density (ASTM D558)• Durability Tests

– Wet-Dry (ASTM D559)– Freeze-Thaw (ASTM D560)

• Soluble Sulfates (ASTM C1580)• Compressive Strength (ASTM D1633)

PCA RecommendedPCA RecommendedParticle SizeParticle Size

Distribution forDistribution forFull-Depth ReclamationFull-Depth Reclamation

• 100% passing a 3-inch sieve

• 95% passing a 2-inch sieve (min)

• 55% passing a No. 4 sieve (min)

Laboratory Mix DesignLaboratory Mix Design• Sieve a sufficient quantity of the roadway

material through the ¾-inch sieve to determine maximum dry density (MDD) and optimum moisture content (OMC) at various cement percentages (ASTM D558)

• Usually about 100 poundsof dry soil is required

• Determine MDD and OMC– 4, 6, and 8 percent cement– By weight of dry material

• Prepare samples with cement– 9 specimens– 3 at each percentage

Strength DeterminationStrength Determination

• Unconfined Compressive Strength Testing– ASTM D1633– Used by most State DOT’s and the FAA– Simple and quick procedure– 7-day strengths ranging

from 300 psi to 400 psiare generally recommended

– Proven strength (support)under heavy traffic conditions

– Proven durability (performance)in both wet-dry and freeze-thawenvironments

Please keep in mind that Please keep in mind that strength and durabilitystrength and durability

are NOT the same thing!are NOT the same thing!

The purpose of themix design procedureis to select thecorrect additive thatmost closely balancesboth strength ANDperformance for theroadway materials!

Determining the thickness ofDetermining the thickness ofFDR pavementsFDR pavements

Commonly used methodsinclude those based onlayer coefficients for thedifferent pavementmaterials and thosebased on a moremechanistic-empiricalapproach.

?

Thickness DesignThickness Design• AASHTO

–Use layer coefficients 0.12 to 0.30–Compare with granular base 0.06 to

0.18–Design Equation:

• Structural Number = a1D1+ a2D2+…+ anDn

D1

D2

D3

3-Layer Pavement Section

a1

a2

a3

LayerCoefficient

Thickness DesignThickness Design• PCA

– Empirical method– Based on subgrade

strength, material type, axle loads,and frequencies

– Publication EB068:Thickness Design forSoil-Cement Pavements

5.75 in

CONSTRUCTIONCONSTRUCTION

An easy construction process whenAn easy construction process whencontrolled by good specifications!controlled by good specifications!

• Processing• Compactin

g• Finishing• Curing• Surfacing

PulverizationPulverization• Pulverize mat to

appropriate gradation• Usually, only one pass

is required!

Material RemovalMaterial Removal(if necessary)(if necessary)

Cement SpreadingCement Spreading• Cement is spread on top of

roadway in measured amount in either a dry or slurry form

Blending of MaterialsBlending of Materialsand Moisture Additionand Moisture Addition

• Cement isblended into pulverized,reclaimedmaterial and, with the addition of water, is brought to optimum moisture

Initial CompactionInitial Compaction

Grading and ShapingGrading and Shaping

• Material is graded to appropriatePlan line,grade, andcross-sections

Final CompactionFinal Compaction• Material is compacted• 98% minimum standard

Proctor density• 5-test average• None below 96%

CuringCuring

Bituminous Compounds(cutbacks or emulsions)

Water(kept continuously moist)

Primary Testing RequirementsPrimary Testing Requirements

Gradation Moisture Density

A common gradation requirement is for 100% to pass a 3-inch (50 mm), a

minimum of 95% to pass a 2-inch (50

mm), and a minimum of 55% to pass a No. 4 (4.75 mm) sieve

(ASTM C 136).

A common density requirement is to be between 95% and 98% of the

established laboratory standard

Proctor density (ASTM D 558).

A common moisture requirement is to be

within 2% of the laboratory established

optimum moisture content (ASTM D

558).

Completed portions of FDR base can be opened immediately to low-speed local traffic and to construction equipment, provided the curing material or moistcuring operationsare not impaired,and provided theFDR base issufficiently stableto withstandmarring orpermanentdeformation.

TrafficTraffic

Subsequent pavement layers (asphalt, chipseal, or concrete) can be placed any time after finishing, as long as the soil-cement is sufficiently stable to support the requiredconstructionequipmentwithout marringor permanentdistortion ofthe surface.

SurfacingSurfacing

Based on 1.6 km of 7.3 m-wide, 2-lane road, with a 150 mm base

Energy Use and MaterialsEnergy Use and MaterialsReclamation -vs- New BaseReclamation -vs- New Base

More AdvantagesMore Advantages• Minimizes inconvenience for both homeowners

and businesses• Less construction and transportation

equipment• Can apply local traffic

almost immediately• Fast operation• Worldwide availability• Familiar to engineers• 25% to 50% cheaper

than removal and replacement!

The The BIGGESTBIGGEST Advantage! Advantage! Versatility through use of portland cement

Stabilizes many materials

HMA or surface treatments

gravel or crushed stone bases

sands, silts, and plastic clays

combinations of all materials“Portland Cement is probably the closest thing we

have to a universal stabilizer.”

Chemical Stabilization Technology for Cold Weather

United States Army Corps of Engineers

September 2002

for additional information, please visit the PCA website at

www.cement.org/pavements

Thank You!

[email protected]